Three-Dimensional Finite Element Analysis of a
Complex Excavation on the MIT Campus
by
MASSACHUSETTS
INSTITUTE
O F TE C
Zhandos Y. Orazalin
Bachelor's Degree in Civil Engineering
Karaganda State Technical University, Kazakhstan (2008)
L IRA R IES
ARCHIVES
Submitted to the Department of Civil and Environmental Engineering
in Partial Fulfillment of the Requirements for the Degree of
Masters of Science in Civil and Environmental Engineering
at the
MASSACHUSSETTS INSTITUTE OF TECHNOLOGY
June 2012
C 2012 Massachusetts Institute of Technology. All rights reserved.
Signature of Author...........
.............................................
Department of Civil and Environmental Engineering
May 21, 2012
~N
C ertified by ..............................................
.
........ ..................
Andrew J. Whittle
Professor of Civil and Environmental Engineering
Thesis Sufrvisor
A c c e pte d by .........................................................
y
. . .......... . . . .
N----Heidi S. Nepf
Chair, Departmental Committee for Graduate Students
Three-Dimensional Finite Element Analysis of a Complex
Excavation on the MIT Campus
by
Zhandos Y. Orazalin
Submitted to the Department of Civil and Environmental Engineering on May 21, 2012
in Partial Fulfillment of the Requirements for the Degree of
Masters of Science in Civil and Environmental Engineering
ABSTRACT
Large excavation projects in urban areas are complex geotechnical problems when it is
necessary not only to ensure the stability of the excavation and support system, but also to
minimize impacts on adjacent buildings and structures. These problems require more
comprehensive analyses that represent the four-dimensional (space-time) processes associated
with performance of the excavation support system.
The goal of this research is to evaluate the use of three-dimensional finite element
analysis in Plaxis 3D 2011 to simulate ground deformations, pore pressures, and diaphragm wall
deflections for the very well instrumented excavation for the basement of the Stata Center on the
MIT campus. The model predictions are compared with the field measurements that include
vertical inclinometers, settlement points, magnet extensometers, and piezometers.
The Ray and Maria Stata Center building at MIT was designed with a basement for
underground parking requiring a 42 ft deep excavation. The excavation was supported by a
perimeter diaphragm wall that formed part of the permanent structure and extended 45 ft into a
deep layer of underlying Boston Blue clay. The diaphragm wall was braced by a combination of
prestressed tieback anchors, preloaded raker and corner bracing support elements. The control of
ground movements was a critical aspect of the subsurface design due to the close proximity of
the excavation to the historical MIT Alumni swimming pool building.
This study has shown that the three-dimensional finite element analysis can be effectively
used for such a complex excavation project and is capable to achieve reasonably consistent
predictions of wall deflections, ground movements, and pore pressures for tieback, cornerbraced, and raker supported diaphragm walls despite of simplifications in the base case model.
The simulation has also captured the three-dimensional effects causing the induced ground
deformations to be smaller near the corner areas. Further numerical analyses are now needed to
assess the importance of soil constitutive behavior on the observed field performance of the
support system for the Stata Center basement.
Thesis Supervisor: Andrew J. Whittle
Title: Professor of Civil and Environmental Engineering
2
ACKNOWLEDGEMENTS
I would like to thank my thesis and research advisor, Professor Andrew Whittle, as well
as my academic advisor, Professor Herbert Einstein for their support and continuous guidance. I
am also very grateful for the opportunity to learn from Dr. John Germaine, Dr. Lucy Jen, and
Professor Ruben Juanes. I express my deep appreciation to my father, Professor Yerbol Orazaly,
and my mother, Azhimova Shara.
Also, I would like to thank all my friends and colleagues at MIT for their support and
encouragement.
3
TABLE OF CONTENTS
A BSTRA CT.................................................................................................................................2
A C KN O WLED GEM EN TS....................................................................................................
3
TA BLE O F C O N TENTS.......................................................................................................
4
List of Figures..............................................................................................................................6
List of Tables...............................................................................................................................11
1 IN TRO D U C TIO N ...................................................................................................................
12
1.1 Problem Statem ent and Research Objectives......................................................................12
1.2 O rganization........................................................................................................................14
2 BA CK G RO U ND ......................................................................................................................
15
2.1 Project D escription............................................................................................................
15
2.2 Subsurface Soil Conditions.............................................................................................
16
2.3 Groundw ater Conditions..................................................................................................
18
2.4 Adjacent Structures............................................................................................................
19
2.5 Excavation Support System .............................................................................................
20
2.6 Construction Sequence....................................................................................................
22
2.7 G eotechnical Instrum entation...........................................................................................
23
3 THREE-DIMENSIONAL FINITE ELEMENT MODEL................................................41
3.1 Base Case Model Assum ptions........................................................................................
41
3.1.1 M odel D escription.......................................................................................................41
3.1.2 Soil Profile......................................................................................................................42
3.1.3 Groundw ater Conditions.............................................................................................
44
3.1.4 Support System s.........................................................................................................
44
4
3.1.4.1 Diaphragm W all and Foundation Properties.............................................................45
3.1.4.2 Corner Bracers Properties...................................................................................
45
3.1.4.3 Rakers Properties......................................................................................................46
3.1.4.4 Tiebacks Properties...............................................................................................
47
3.2 Development of the Three-Dimensional Model in Plaxis 3D.........................................
49
3.2.1 Excavation Sequence and Phases..............................................................................
49
3.2.2 Com plex G eometry Design........................................................................................
49
4 RESU LTS A N D INTERPRETATION ..............................................................................
68
4.1 Wall D eflections...................................................................................................................68
4.2 Pore Pressures.......................................................................................................................72
4.3 Excavation H eave.................................................................................................................74
4.4 Surface Settlem ents...............................................................................................
.... 75
4.5 Structural Loads....................................................................................................................76
4.6 Effects of Partial Drainage...............................................................................................
5 SU M M A RY A ND CO NCLUSIO NS .....................................................................................
76
126
5.1 Sum mary..........................................................................................................................126
5.2 Conclusion..........................................................................................................................127
REFERENCES ..........................................................................................
129
A PPEND IX 1..............................................................................................................................
134
A PPENDIX 2 ..............................................................................................................................
135
A PPEND IX 3..............................................................................................................................137
5
List of Figures
Figure 2-1: Map of MIT Campus showing the location of the Stata Center.............................29
Figure 2-2: View of MIT Stata Center building.......................................................................30
Figure 2-3: Project Plan and Adjacent Buildings Location....................................................
31
Figure 2-4: Geotechnical Instrumentation Location Plan.........................................................32
Figure 2-5: Subsurface Profiles Plan........................................................................................
33
Figure 2-6: Subsurface Profiles A, B, and C............................................................................34
Figure 2-7: Subsurface Profiles D and E................................................................................
35
Figure 2-8: In-Site Stress and Pore Pressure vs. Elevation.......................................................36
Figure 2-9: Undrained Shear Strength Profile.........................................................................37
Figure 2-10: General Trends in Excavation............................................................................
38
Figure 2-11: Typical Cross-Section of Tiebacks and Excavation...........................................39
Figure 2-12: Typical Cross-Section of Rakers and Excavation................................................40
Figure 3-1: Schematic plan of structural support system with dimensions...............................59
Figure 3-2: CAD model of the support system..........................................................................59
Figure 3-3: Example of excavation modeling - Phase #3 (12/05/2001)....................................60
Figure 3-4: Example of excavation modeling - Phase #30 (5/08/2001)....................................61
Figure 3-5: CAD Model (simple case) - creation of full cluster................................................62
Figure 3-6: CAD Model (simple case) - creation of input cluster based on available
info rm ation .....................................................................................................................................
62
Figure 3-7: CAD Model (simple case) - subtracting input cluster from full cluster.................63
Figure 3-8: CAD Model (simple case) - mesh tessellation settings for cluster conversion..........63
Figure 3-9: CAD Model (simple case) - converted cluster.......................................................64
Figure 3-10: CAD Model (simple case) - converted cluster preparation................................64
Figure 3-11: Importing prepared soil cluster into the Plaxis 3D model....................................65
6
Figure 3-12: CAD Model (complex case) - input cluster based on available information..........65
Figure 3-13: CAD Model (complex case) - inversion of input cluster....................................66
Figure 3-14: CAD Model (complex case) - subtracting new input cluster from previous phase
6
clu ster.............................................................................................................................................6
Figure 3-15: CAD Model (complex case) - input cluster differentiated...................................67
Figure 3-16: CAD Model (complex case) - mesh tessellation settings for cluster
conversio n......................................................................................................................................
67
Figure 4-1: Wall deflections measured by inclinometers SC-04 and SC-05 along the East Wall
vs. 3D Finite Element Analysis predictions (Base Case A).......................................................78
Figure 4-2: Wall deflections measured by inclinometers SC-06 through SC-08 along the South
Wall vs. 3D Finite Element Analysis predictions (Base Case A).............................................79
Figure 4-3: Wall deflections measured by inclinometers SC-09 through SC- 11 along the West
Wall vs. 3D Finite Element Analysis predictions (Base Case A).............................................80
Figure 4-4: Wall deflections measured by inclinometers SC-01 through SC-03 along the North
Wall vs. 3D Finite Element Analysis predictions (Base Case A).............................................81
Figure 4-5: Excavation Progress on December 5, 2000 and 3D Finite Element Analysis
Predictions (B ase C ase A )........................................................................................................
82
Figure 4-6: Excavation Progress on December 19, 2000 and 3D Finite Element Analysis
Predictions (B ase C ase A ).........................................................................................................
83
Figure 4-7: Excavation Progress on December 27, 2000 and 3D Finite Element Analysis
Predictions (B ase C ase A ).........................................................................................................
84
Figure 4-8: Excavation Progress on January 11, 2001 and 3D Finite Element Analysis
Predictions (B ase C ase A )........................................................................................................
85
Figure 4-9: Excavation Progress on January 17, 2001 and 3D Finite Element Analysis
Predictions (B ase C ase A )........................................................................................................
86
Figure 4-10: Excavation Progress on January 29, 2001 and 3D Finite Element Analysis
Predictions (B ase C ase A )........................................................................................................
87
Figure 4-11: Excavation Progress on February 6, 2001 and 3D Finite Element Analysis
Predictions (B ase C ase A )........................................................................................................
88
7
Figure 4-12: Excavation Progress on February 13, 2001 and 3D Finite Element Analysis
Predictions (B ase Case A )........................................................................................................
89
Figure 4-13: Excavation Progress on February 23, 2001 and 3D Finite Element Analysis
Predictions (B ase C ase A ).........................................................................................................
90
Figure 4-14: Excavation Progress on March 14, 2001 and 3D Finite Element Analysis
Predictions (B ase Case A ).........................................................................................................
91
Figure 4-15: Excavation Progress on April 25, 2001 and 3D Finite Element Analysis Predictions
(B ase C ase A )................................................................................................................................92
Figure 4-16: Excavation Progress on May 8, 2001 and 3D Finite Element Analysis Predictions
3
(B ase C ase A )................................................................................................................................9
Figure 4-17: Excavation Progress on May 17, 2001 and 3D Finite Element Analysis Predictions
(Base C ase A )................................................................................................................................94
Figure 4-18: Wall Deflections Comparison Technique for the North Wall - Measured Data vs.
95
Simulation (B ase C ase A ).........................................................................................................
Figure 4-19: Wall Deflections Comparison Technique for the East Wall - Measured Data vs.
Simulation (B ase C ase A ).........................................................................................................
96
Figure 4-20: Wall Deflections Comparison Technique for the South Wall - Measured Data vs.
97
Simulation (B ase C ase A ).........................................................................................................
Figure 4-21: Wall Deflections Comparison Technique for the West Wall - Measured Data vs.
98
Simulation (B ase C ase A ).........................................................................................................
Figure 4-22: Piezometric elevations measured by PZ-1 vs. 3D Finite Element Analysis
predictions (B ase C ase A ).........................................................................................................
99
Figure 4-23: Piezometric elevations measured by PZ-2 vs. 3D Finite Element Analysis
predictions (B ase C ase A )............................................................................................................100
Figure 4-24: Piezometric elevations measured by PZ-3 vs. 3D Finite Element Analysis
predictions (B ase C ase A )............................................................................................................10
Figure 4-25: Piezometric elevations measured by PZ-4 vs. 3D Finite Element Analysis
predictions (B ase C ase A )............................................................................................................102
Figure 4-26: Piezometric elevations measured by PZ-5 vs. 3D Finite Element Analysis
predictions (B ase C ase A )............................................................................................................103
8
1
Figure 4-27: Vertical Ground Movements measured by EXT-I (upper level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................104
Figure 4-28: Vertical Ground Movements measured by EXT-I (lower level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................105
Figure 4-29: Vertical Ground Movements measured by EXT-2 (upper level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................106
Figure 4-30: Vertical Ground Movements measured by EXT-2 (lower level) vs. 3D Finite
Element Analysis predictions (Base Case A)..............................................................................107
Figure 4-31: Vertical Ground Movements measured by EXT-3 (upper level) vs. 3D Finite
Element Analysis predictions (Base Case A)..............................................................................108
Figure 4-32: Vertical Ground Movements measured by EXT-3 (lower level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A )..............................................................................109
Figure 4-33: Vertical Ground Movements measured by EXT-4 (upper level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................110
Figure 4-34: Vertical Ground Movements measured by EXT-4 (lower level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................111
Figure 4-35: Vertical Ground Movements measured by EXT-5 (upper level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................112
Figure 4-36: Vertical Ground Movements measured by EXT-5 (lower level) vs. 3D Finite
Elem ent Analysis predictions (Base Case A)..............................................................................113
Figure 4-37: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the East wall vs. measured data (June 1, 2001)...............................................................114
Figure 4-38: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the South wall vs. measured data (June 1, 2001).............................................................115
Figure 4-39: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the W est wall vs. measured data (June 1, 2001)..............................................................116
Figure 4-40: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the North wall vs. measured data (June 1, 2001).............................................................117
Figure 4-41: Settlement contours for the East wall based on compiled data from the surface
settlement points vs. 3D Finite Element Analysis predictions (Base Case A)............................118
9
Figure 4-42: Settlement contours for the North wall based on compiled data from the surface
settlement points vs. 3D Finite Element Analysis predictions (Base Case A)............................119
Figure 4-43: Settlement contours for the North wall based on compiled data from the surface
settlement points vs. 3D Finite Element Analysis predictions (Base Case A)............................120
Figure 4-44: Settlement contours for the West wall based on compiled data from the surface
settlement points vs. 3D Finite Element Analysis predictions (Base Case A)............................121
Figure 4-45: 3D Finite Element Analysis predictions (Base Case A) of tieback loads vs. time
alon g the E ast w all.......................................................................................................................122
Figure 4-46: 3D Finite Element Analysis predictions (Base Case A) of tieback loads vs. time
along the West w all.....................................................................................................................123
Figure 4-47: 3D Finite Element Analysis predictions (Base Case A) of tieback loads vs. time
along the South w all.....................................................................................................................124
Figure 4-48: 3D Finite Element Analysis predictions-Case B (Partial Drainage Analysis) vs.
B ase C ase A (U ndrained Analysis)..............................................................................................125
10
List of Tables
Table 2-1: Summary of construction activities with corresponding dates...............................
25
Table 2-2: Details for the tiebacks at the MIT Stata Center....................................................
26
Table 2-3: Details for Corner Bracing at the MIT Stata Center.............................................
27
Table 2-4: Details for Raker Supports at the MIT Stata Center.............................................
28
Table 3-1: Summary of Plaxis 3D Materials Properties - Soils...............................................
51
Table 3-2: Summary of Plaxis 3D Materials Properties - Node-to-node Anchors..................
52
Table 3-3: Summary of Plaxis 3D Materials Properties - Plates.............................................
52
Table 3-4: Summary of Plaxis 3D Materials Properties - Embedded piles..............................53
T able 3-5: Calendar plan...........................................................................................................
54
Table 3-6: Full list of Plaxis 3D phases with correlated duration time....................................55
Table 3-7: Details of Plaxis 3D Model Phases.........................................................................
11
56
1 INTRODUCTION
1.1 Problem Statement and Research Objectives
Large excavation projects in urban areas are complex geotechnical problems where it is
necessary not only to ensure the stability of the excavation and support system, but also to
minimize impacts on adjacent buildings and structures. These problems require more
comprehensive analyses that represent the four-dimensional (space-time) processes associated
with performance of the excavation support system. The goal of this research is to evaluate the
use of three-dimensional finite element analysis (using a commercial Finite Element Analysis
code, Plaxis 3D 2011) to simulate ground deformations, pore pressures, and diaphragm wall
deflections for the very well instrumented excavation for the basement of the Stata Center on the
MIT campus.
The Ray and Maria Stata Center building at MIT was designed with a basement for
underground parking requiring a 42 ft deep excavation. The excavation was supported by a
perimeter diaphragm wall that formed part of the permanent structure and extended 45 ft into a
deep layer of underlying Boston Blue clay. The diaphragm wall was braced by a combination of
prestressed tieback anchors, preloaded raker and corner bracing support elements. The control of
ground movements was a critical aspect of the subsurface design due to the close proximity of
the excavation to the historical MIT Alumni swimming pool building. The construction history
and measured performance of the excavation support system were documented in the SM thesis
by Olsen (2001).
The development of the three-dimensional finite element model for the Stata Center
constitutes a challenging task, because it not only requires a reliable modeling of the constitutive
behavior of the soil coupled with groundwater seepage flow, but also needs to represent a large
12
range of structural support system elements and a complex non-uniform excavation process. The
complexity of the project has defied previous attempts at three-dimensional modeling. However,
with the latest generation of Plaxis 3D 2011, we now have the advantage of a suitable threedimensional flow-deformation analysis tool to create a comprehensive model of the entire
excavation project with more than 300 tieback and raker support elements. This analysis is the
first attempt to use these modem tools for a well-documented case history.
Therefore, the main research objective is to evaluate the use of three-dimensional finite
element analysis to simulate ground deformations, pore pressures, and diaphragm wall
deflections for this very well instrumented excavation. The model predictions are compared with
the
field
measurements
that
include
vertical
inclinometers,
settlement points,
magnet
extensometers, and piezometers. The thesis provides full results of the analysis and detailed
directions to reproduce the base case model predictions.
This study is a part of research with the goal to investigate the key parameters affecting
the excavation performance and the predictive capabilities of the three-dimensional finite
element analysis applied to geotechnical engineering problems. Taking into account the
complexity of the project and challenges of a three-dimensional analysis, a base case simulation
with a simple soil model was needed in order to obtain preliminary results. Several models have
been developed, calculated and carefully analyzed. Two of them are presented and discussed in
detail - the Base Case Model (A), which assumes undrained conditions within the clay, and the
Model (B), which takes into account the effects of partial drainage. Both models simulate the
adjacent swimming pool building as a three-dimensional surface surcharge (1.28ksf). All three
dimensional models are currently limited to a Mohr-Coulomb soil model, which represents a
13
reasonable "first-order" approximation of soil behavior and is defined by input parameters that
specify the linear elastic behavior (E, v') and yield conditions (c',
#').
1.2 Organization
Chapter 2 provides background information for this thesis and presents the description of
the excavation project used as a case study for the three dimensional finite element analysis. The
chapter includes a detailed overview of the excavation support system and construction history
of the project. It also describes the subsurface soil and groundwater conditions of the site and
geotechnical instrumentation used to monitor the excavation performance.
Chapter 3 describes the development of the three dimensional finite element model and
the base case model assumptions. That includes the information on the soil profile, groundwater
and boundary conditions and properties of the structural elements. The process of modeling
complex geometries for large three dimensional analyses is also fully described.
Chapter 4 presents and evaluates the results obtained from the base case model. The
model predictions include wall deflections, pore pressures, surface settlements, excavation heave
and structural loads. These results are compared with the field measurements. Also, the observed
three dimensional effects are discussed in detail.
Chapter 5 contains a summary of the thesis. The conclusions are summarized and
recommendations from this work are presented. Chapter 5 is followed by three appendices. They
include all the necessary details to recreate the three dimensional model of the excavation for the
basement of the Stata Center at MIT in Plaxis 3D 2011.
14
2 BACKGROUND
2.1 Project Description
The Ray and Maria Stata Center is an academic complex designed by renowned architect
Frank Gehry for the Massachusetts Institute of Technology (MIT). The building is home to the
Computer Science and Artificial Intelligence Laboratory (CSAIL), the Laboratory for
Information and Decision Systems (LIDS) and the Department of Linguistics and Philosophy.
The Stata Center has become "iconic" and well known due to its impressive design featuring
unusual shapes such as tilting towers and many-angled walls (Figure 2-2). It also has a great
number of sustainable design elements that include innovative storm water retention and
management system, as well as demand controlled ventilation system.
The underground part of the Stata Center building was complete in a period of 11 months
from July 2000 to June 2001. Almost 5 months of this period were spent on the slurry wall
construction which was accomplished in early November, 2000. The mass excavation for the
Stata Center building started on November 14, 2000, and the project was believed to be the
largest open excavation in the history of Cambridge (Joyce, 2004). Nevertheless, the excavation
work and associated support system installation were successfully completed as scheduled on
June 19, 2001. The construction dates with the time frame for the excavation and associated
support system are summarized in Table 2-1.
The site for the MIT Stata Center has a very large rectangular plan area (approx. 320ft x
390ft), which abuts an existing building along its southern edge (Figure 2-3). A floating mat
foundation system was designed so that the weight of the building is balanced against the weight
of the soil extracted from the site. The excavation support system comprises a reinforced 30
inches thick concrete diaphragm wall that is supported through the use of: 1) three levels of
15
tiebacks on the west, south, and east sides, 2) two levels of corner bracing, and 3) two levels of
raker supports on the north side.
Tiebacks were installed at an angle of 20 degrees from the horizontal at El. 10, El. -1, and
El. -10 and preloaded from 112 to 128 kips. Two levels of corner bracing consisting of 36-indiameter pipe struts were installed at El. 10 and El. -10.
The City of Cambridge prohibited the installation of tiebacks beneath the Vassar street
such that two levels of inclined raker bracing (at El. 10 and El. -10) were used along the North
side of the excavation. The raker bracing consisted of 36-in-diameter pipe struts extending from
embedded plates in the diaphragm wall to kicker blocks embedded in the concrete mat
foundation.
2.2 Subsurface Soil Conditions
The site is situated on filled land within the Charles River Basin at the east side of the
MIT campus in Cambridge, Massachusetts (Figure 2-1). In preparation for the design and
construction of the Stata Center a geotechnical exploration program and specialized laboratory
testing (at MIT Geotechnical Laboratory) were undertaken to provide data on the engineering
properties of the soil underlying the proposed building location. The subsurface exploration
program consisted of 20 shallow test borings, 2 deep borings, and 10 piezocone tests advanced to
refusal in the glaciomarine deposits or bedrock (Hewitt, et al., 2003). Piezocone testing was used
to identify sand layers and lenses within the marine clay and to recognize relative changes in
stress history and undrained shear strength profile.
A typical subsurface profile underlying the Stata Center in the middle of the site would
consist of 11 ft of fill, 6 ft of organics, 14 ft of sand, 85 ft of clay, and 15 ft of glacial till. The
16
principal stratum is the marine clay (Boston Blue Clay) - which can be sub-divided into an upper
overconsolidated clay crust and a lower normally consolidated unit. Five subsurface profiles
(location is schematically drawn in Figure 2-5) showing soil and water conditions, adjacent
structures, and the Stata Center excavation are shown in Figures 2-6 and 2-7.
The description of the subsurface layers can be found below, proceeding downward from
the ground surface (Hewitt, et al., 2003):
1) Miscellaneous Granular Fill - the layer consists of coarse to fine sand or gravelly sand,
with varying amounts of cinders, glass, brick, rubble, and wood. It varies in density from loose to
dense with an average Standard Penetration Test N value of 15 and ranges in thickness from 5 to
19 ft.
2) Organic Silt and Peat - a deposit of organic silt and peat is a soft, gray, compressible
layer containing some fibers, and interbedded with peat that is soft, brown, and fibrous. The
stratum thickness varies from 4 to 22 ft. Some fine sand and shells are present.
3) Marine Sand - the marine sand stratum is a dense, gray, fine to medium sand with
some gravel. It ranges in thickness from 0.5 to 16.5 ft and the top of the layer is located at depths
ranging from 13 to 30 ft. (El. +7 ft to -11 ft). The Standard Penetration Test blow counts ranged
from 19 to 32 blows/ft.
4) Marine Clay - the Boston Blue Clay consists of medium stiff to stiff, silty clay with
occasional fine sand seams. This stratum is typical of the Boston area with an upper layer
consisting of a stiff crust, becoming softer and more compressible with depth. The thickness of
the clay varies from 55 to 90 ft within the location of the Stata Center. Undrained shear strength
profiles (Figure 2-9) were developed from the laboratory CRS data using SHANSEP procedure.
As recommended by Berman et al. (1993), the SHANSEP parameters m=0.77 and S=0.205 were
17
used to determine the undrained shear strength (Hewitt, et al, 2003). The profiles typically
decrease from 1,600 psf to 1,300 psf at El. -55 ft, and then increase to a maximum of 1,900 psf
at the bottom of the marine clay.
5) Glacial Till -a heterogeneous layer of dense sand, gravel, silt, clay and boulders was
encountered underlying the marine deposits (Boston Blue Clay). This glaciomarine deposits
appear to vary in thickness from 5 ft to possibly 20 ft in some places with it averaging roughly
12 ft in thickness.
6) Bedrock - the bedrock is a part of the Cambridge Argillite formation, which is a
relatively soft gray sedimentary rock. Bedrock is encountered at depths approximately 131 ft (El.
-110 ft).
2.3 Groundwater Conditions
Two groundwater observation wells were installed in the test borings HA-I and HA-5 on
the northeast and southwest sides of the site (Figure 2-4). Groundwater was observed in
completed test borings at depths ranging from El. 5 ft to El. 11 ft. The water level in the wells
was also checked right before excavation work began and was found to be at El. 14.0 ft and El.
14.2 ft, respectively. The groundwater table elevation is affected by a great number of factors
with include below-grade structures, precipitation, local construction activity, pumping of
dewatering systems, leakage from utilities, and seasonal variations. The water level in the
Charles River is maintained in the range of El. 12 to El. 13. Although previous investigations
have found that the water pressures in the clay and underlying till are higher than hydrostatic by
about 5 ft to 7 ft of head (Berman, 1993), there was no evidence to support these conditions
18
during investigations or construction of the Stata basement. As a result, hydrostatic pressures
were used for the design calculations (Olsen, 2001).
2.4 Adjacent Structures
As can be seen in Figure 2-3, the Stata Center site is surrounded by existing structures.
The adjacent structures can impact both the performance and the design of the excavation
support systems; therefore, all adjacent buildings were carefully studied and documented. Figure
2-3 shows the locations and foundation systems of for these adjacent buildings.
Building 36 is located to the west of the site near the northwest corner, 24-ft from the
diaphragm wall, and is a 9-story concrete building with two belowgrade levels. The building is
built on a mat foundation bearing on the marine sand at El. -2 ft.
Building 26 is a 5-story concrete structure with a penthouse and one below-grade level
situated to the west of the site 54 ft from the diaphragm wall. The foundation system is footings
bearing on the marine sand at El. 1 ft.
Building 57, the MIT Alumni Pool Building, is a 3-story building with a swimming pool
that extends below grade. It is located to the south of the site at a distance of approximately 3.5 ft
from the diaphragm wall. The structure is supported by belled concrete caissons bearing
primarily in the marine sand at El. -12 ft with a typical shaft diameter of 3-ft with the bells
varying from 3 to 10 ft. The loads supported by these caissons vary from 80 to 320 kips.
Building 70 was a parking garage (since demolished) with 8 stories with a below grade
level located to the east of the site with the nearest point 28-ft from the Stata Center. The
foundation system comprises pressure injected footings bearing in the marine sand at El. -6.25
ft.
19
Vassar Street is a two lane road that is approximately 45 ft wide located to the north of
the site and at its nearest point is 20 ft from the diaphragm wall. A great number of utilities are
located beneath the street which have affected the design of the excavation support system.
2.5 Excavation Support System
The wall system consists of a 30 in reinforced concrete diaphragm wall as the permanent
basement wall. The slurry wall was comprised of 65 diaphragm wall panels that were installed
with numbering starting in the southwest corner and continuing counter-clockwise around the
perimeter. The wall was designed to extend to El. -50 ft (approximately 28 ft into the marine
clay deposits) top elevation varying from El. 15.4 ft to El. 19.0 ft with the surface at El. 21.0 ft.
The wall was designed to support loads through skin friction but not through end-bearing. The
diaphragm wall was cast in-situ with sleeves pre-installed to simplify the installation of tieback
anchors. The bearing plates were also used to strengthen the contact areas with corner braces and
rakers.
The foundation consists of a 4.0 ft thick reinforced concrete slab (mat foundation). At the
excavation level of El. -21 ft, a concrete mud mat was placed to stabilize the surface of the clay
and to make it easier to construct the reinforcing cage for the slab, as well as to pour it. The top
of the mat foundation is at El. -16.6 ft.
The support system was designed with a total of 289 tiebacks spread out on the south,
east, and west sides of the site to provide lateral support. They were installed at El. 10.0 ft, -1.0
ft, and -12.0 ft and inclined at an angle of 200. The design loads are 112 kips for the top level
and 128 kips for the second and third levels. The tiebacks were designed to have total lengths of
90 ft, 48 ft, and 38 ft, with bond lengths of 40 ft, 50 ft, and 50 ft for first, second, and third levels
respectively. A typical cross section showing the tiebacks and the diaphragm wall with the
20
excavation progress is in Figure 2-11. The tiebacks details can be found in Table 2-2. The
tiebacks each consist of 4, 0.6 in. diameter high strength steel tendons (270 ksi) where the free
lengths are sheathed with a polyethylene tube material to preclude bonding in that portion. The
Type 1/11 Portland Cement with water to cement ratio of 0.49 by weight and a minimum 28 day
compressive strength of 4,000 psi was used in the grouted anchors.
The tiebacks are drilled with a casing through the layers of fill, organics, and sand using
internal flush methods deep into the overconsolidated clay crust. Each drilled hole is filled with
grout and the tendon and post-grouting pipes are inserted while the casing is removed. The postgrouting pipe consists of a 0.75 in PVC pipe with holes, so post-grouting can be undertaken
(instead of redrilling) if the anchor fails to achieve its proof load. The grout can be applied at
pressures up to 800 psi if post-grouting is necessary. The tiebacks will then be locked-off at
100% of their design load once the grout has had time to set. All tiebacks are also proof tested to
130% of their design load.
The corner bracing consists of 36 in diameter steel pipe struts that are installed at El. 10 ft
and El. -10 ft. The pipe struts were pre-loaded by jacking them in place at 50% of their design
load. The details for corner bracing support can be found in Table 2-3 (design loads, jacking
loads, and strut sizes). The numbering system used to identify each corner brace identifies the
comer location, the bracing level (1 for El 10 ft and 2 for El -1Oft), and its position from the
corner (starting from the closest to the corner).
The support system for the north wall comprises two levels of raker struts that transfer
earth pressures to the mat foundation (and transferring the load through basal shear resistance
across to the south wall). The construction sequence assumes that a large portion of the site will
be excavated to final grade leaving a 20 ft berm in front of the north wall. The foundation mat is
21
poured from the south wall and the rakers are then set in place and pre-loaded. Each raker
comprises a 36 in diameter steel pipe strut that supports the wall (at El 10 ft and El -10 ft) and is
inclined downward to a kicker block cast into the mat. They are also pre-loaded to 50% of their
design load. Figure 2-12 shows a typical cross section of rakers and excavation progress. The
details for each of the rakers can be found in Table 2-4.
2.6 Construction Sequence
The MIT Stata Center project started with the installation of the reinforced concrete
diaphragm wall using the slurry trench method. This was accomplished from July to November
2000, a period of approximately 5 months. A grouting program was undertaken to strengthen the
sand layer below building 57 to minimize settlements due to loss of ground for the wall directly
adjacent to its foundation prior to installation of the south wall.
The excavation began approximately in November of 2000, after the perimeter
diaphragm wall installation. Dewatering wells were installed within the excavation to maintain
the water table below the excavation grade. Two groundwater observation wells were set up
outside of the diaphragm wall (Figure 2-4) and recorded no appreciable lowering of the water
table surrounding the site during this process. The excavation work developed a general trend of
progressing from the southwest toward the northeast. At each grade elevation, the excavation
progresses from the southwest corner northwards along the west wall to enable installation of
tieback anchors (Figure 2-1). The next phases included the excavation along the south wall and
then north along the east wall (#2 and #3 in Figure 2-10). The soil in the middle of the site was
kept as a central surcharge to improve the stability of the lateral earth support system. Next, the
excavation was gradually pulled back northward, as shown in Figure 2-10. This same pattern was
repeated for each tieback levels. The north side was left to the end in order to install the raker
22
supports. Support installation progressed as quickly as the tiebacks could be installed by the drill
rigs, as well as the corner bracing could be fabricated on site and put in place.
The excavation process was constantly monitored, described in the daily field logs and
recorded on the webcams located around the site; numerous photos were also taken during the
each construction phase. The summary of construction activities with corresponding dates is
presented in Table 2-1.
2.7 Geotechnical Instrumentation
The performance of the excavation support was monitored throughout the excavation in
order to ensure that movements were within acceptable limits and to mitigate possible damage to
the surrounding structures. Any movement toward the excavation generates settlements and
lateral deformations in the retained soil. Therefore, one of the main potential causes of damage to
surrounding structures is the movement of the diaphragm wall into the excavation. This damage
is primarily related to the differential settlement and lateral strain between structural supports
(Boscardin, 1989). A system of instruments that included vibrating wire piezometers, magnetic
extensometers, vertical inclinometers, groundwater observation wells, and settlement points was
implemented in order to monitor the movements and provide advance warning of any potential
failures.The instrumentation plan is shown in Figure 2-4.
The vibrating wire piezometers are used to determine changes in pore pressure within the
clay layer and can reflect changes in groundwater pressure due to overburden release, pumping,
or inflows into the excavation. This information is essential for calculating changes in the
effective stress within the clay (and hence, estimating soil settlement).
23
The magnetic extensometers consist of magnets positioned at various depths in a
borehole pipe. A probe passing through the pipe detects the adjacent magnets and its location is
recorded. The distribution of vertical deformations can be measured within the soil column by
recording these locations over time.
The vertical inclinometers are tubes that are located vertically within the diaphragm wall.
The bottom of these pipes is fixed in the bedrock. Lateral deformations are measured by
integrating tilt measurements from a torpedo probe pulled through the tube. The inclinometers
are marked on all drawings as SC-x, where "x" is the number of the inclinometer.
The settlement points consist primarily of metal screws that are fixed to buildings or
sidewalks. They are then optically surveyed to measure whether or not a building or the ground
surface are moving. The measured data is logged over the full period of construction and beyond.
To sum up, a total of 11 inclinometers, 12 piezometers, 2 observational wells, 5 borehole
extensometers, and between 100 and 150 settlement points were installed and monitored. These
data are presented, analyzed and compared with the three dimensional finite element analysis
results in Chapter 4.
24
Table 2-1: Summary of construction activities with corresponding dates
Construction activities
Description
Start Date
End Date
Duration
Diaphragm Wall installation
July, 2000
November, 2000
-150 days
First Level of West Tiebacks
12/05/00
12/27/00
22 days
First Level of South-West Bracing
12/06/00
12/13/00
7 days
First Level of South Tiebacks
12/21/00
01/05/01
15 days
First Level of South-East Bracing
12/18/00
01/05/01
18 days
First Level of East Tiebacks
01/02/01
01/09/01
7 days
First Level of North-West Bracing
01/08/01
01/17/01
9 days
Second Level of West Tiebacks
01/02/01
01/18/01
16 days
Second Level of South Tiebacks
01/12/01
01/23/01
11 days
Second Level of East Tiebacks
01/23/01
02/01/01
9 days
Second Level of South-West Bracing
01/22/01
01/29/01
7 days
Third Level of West Tiebacks
01/29/01
02/09/01
11 days
Third Level of South Tiebacks
02/02/01
02/20/01
18 days
Second Level of South-East Bracing
02/02/01
02/16/01
14 days
Third Level of East Tiebacks
02/21/01
03/26/01
33 days
First Level of North-East Bracing
03/06/01
03/14/01
8 days
Second Level of North-West Bracing
04/25/01
05/01/01
6 days
Foundation slab at the center
03/03/01
04/25/01
53 days
First Level of Raker support
04/06/01
05/15/01
39 days
Second Level of Raker support
05/09/01
06/01/01
23 days
Second Level of North-East Bracing
05/30/01
06/06/01
7 days
Excavation process
11/14/00
06/19/01
-217 day
25
Table 2-2: Details for the tiebacks at the MIT Stata Center (adapted from Olsen, 2001)
Number of Design Load
Wall
Tiebacks
Prestressing
Installed
Free
Bond
ITiebacks I
(kips)
Load (kips)
South S1-1 to Sl-45
S2-1 to S2-45
S3-1 to S3-45
45
45
45
112
128
128
112
128
128
20
20
20
50
20
10
40
50
50
East
E1-1 to El-25
E2-1 to E2-25
E3-1 to E3-25
25
25
25
112
128
128
112
128
128
20
20
20
50
20
10
40
50
50
West
1-1 to Wl-2
W2-1 to W2-2
W3-1 to w3-27
26
26
27
112
128
128
112
128
128
20
20
20
50
20
10
40
50
50
26
Angle (deg) Length (ft) Length (ft)
Table 2-3: Details for Corner Bracing at the MIT Stata Center (after Olsen, 2001)
Unbraced
Length
Design Load
(normal to
the wall)
Tributary
Length
Angle B/N
Strut and
Wall
Diameter
Wall
Thickness
Design
Load
Jacking
Load
(in)
(in)
(kips)
(kips)
Strut Size
Elevation
Length
Strut
(ft-CCB)
(1f)
(ft)
(kips/ft)
(ft)
(degrees)
NW1-1
10
8.6
8.6
26
16.25
40.39
NWI-2
NW1-3
10
10
40.8
76.6
40.8
38.3
26
26
24.25
24.25
40.4
40.4
36
36
NWI-4
10
114.7
57.4
26
25
40.4
36
NW2-1
NW2-2
NW2-3
NW2-4
-10
-10
-10
-10
8.6
40.8
76.6
114.7
8.6
40.8
38.3
57.4
44
44
44
44
16.25
24.25
24.25
25
40.39
40.4
40.4
40.4
36
36
36
SWI-1
10
7.8
7.8
26
16.25
45
598
0
SW1-2
10
37.8
37.8
26
23.25
45
36
0.38
855
427
SWI-3
10
73.2
73.2
26
14.25
45
36
0.38
524
262
SW2-1
SW2-2
SW2-3
-10
-10
-10
7.8
37.8
73.2
7.8
37.8
73.2
44
16.25
23.25
14.25
45
W14X132
0.519
0.519
1011
1447
887
0
723
443
NE1-1
NE1-2
NEI-3
NEI-4
10
10
10
10
7.8
7.8
26
W14X90
37.8
36.6
54.3
26
26
26
16.25
25
25
25
45
37.8
73.2
108.5
45
45
45
36
36
36
598
919
919
919
0
460
460
460
NE2-1
NE2-2
NE2-3
NE2-4
-10
-10
-10
-10
7.8
37.8
73.2
108.5
7.8
37.8
36.6
54.3
44
44
44
44
16.25
25
25
25
45
45
45
45
36
36
36
W14X132
0.519
0.519
0.63
1011
1556
1556
1556
0
778
778
778
SE1-1
SE1-2
10
10
7.8
20.2
7.8
20.2
26
26
10.84
19.59
45
48.09
W14X90
36
0.38
398
720
0
360
SEI-3
SE1-4
SEI-5
10
10
10
55.5
90.9
121.3
55.5
45.5
60.7
26
26
26
25
23.25
14.25
46.32
45.84
45.95
36
36
36
0.38
0.38
0.38
919
855
524
460
427
262
SE2-1
-10
7.8
7.8
44
10.84
45
674
0
SE2-2
-10
20.2
20.2
44
19.59
48.09
36
0.393
1219
609
SE2-3
SE2-4
SE2-5
-10
-10
-10
55.5
90.9
121.3
55.5
45.5
60.7
44
44
44
25
23.25
14.25
46.32
45.84
45.95
36
36
36
0.63
0.519
0.393
1556
1447
887
778
723
443
ME
--
44
44
-Tm
-
45
45
W14X90
555
0
0.38
0.38
828
828
414
414
0.38
853
427
0.519
0.519
0.63
939
1401
1401
1444
0
700
700
722
W14X120
W14X90
36
36
0.38
0.38
0.38
W14X90
*NOTE: This is the location of the strut described, with NW1 -1 meaning Northwest comer level one nearest brace to the corner.
-
-
Table 2-4: Details for Raker Supports at the MIT Stata Center (after Olsen, 2001)
00
Raker*
N1-1
N1-2
N1-3
N1-4
NI-5
NI-6
N1-7
N1-8
Elevation
(@north wall)
(ft-CCB)
10
10
10
10
10
10
10
10
Overall
Length
(ft)
88.6
88.7
89.5
89
88.6
88.6
88.6
89.3
Unbraced
Length
(ft)
88.6
88.7
89.5
89
88.6
88.6
88.6
89.3
Design Load
(normal to
the wall)
(kips/ft)
26
26
26
26
26
26
26
26
N2-1
N2-2
N2-3
N2-4
N2-5
N2-6
N2-7
N2-8
-10
-10
-10
-10
-10
-10
-10
-10
85.2
85.6
86.9
86.2
85.2
85.2
85.2
85.4
85.2
85.6
86.9
86.2
85.2
85.2
85.2
85.4
44
44
44
44
44
44
44
44
Tributary
Length
(ft)
25
23.5
23.5
24
24
25
25
25
Angle B/N
Raker and
Wall
(vertical)
(degrees)
16.61
16.61
16.61
16.61
16.61
16.61
16.61
16.61
Angle B/N
Raker and
Wall
(horizontal)
(degrees)
91.53
87.18
81.61
84.54
91.53
91.53
91.53
97.14
25
23.5
23.5
24
24
25
25
25
3.6
3.6
3.6
3.6
3.6
3.6
3.6
3.6
91.53
84.18
78.65
81.06
91.53
91.53
91.53
94.14
Strut Size
Wall
Diameter Thickness
(in)
in)
36
0.519
36
0.519
36
0.519
36
0.519
36
0.519
36
0.519
36
0.519
36
0.519
36
36
36
36
36
36
36
36
0.803
0.803
0.803
0.803
0.803
0.803
0.803
0.803
Design
Load
(kips)
678
638
644
652
650
678
678
683
Jacking
Load
(kips)
339
319
322
326
325
339
339
341
1103
1041
1057
1070
4057
1103
1103
1105
551
521
528
535
529
551
551
553
*NOTE: Raker Name is given as first: location, second: level, third: number from west to east(ie. N1-1 means North raker level one farthest west)
Figure 2-1: Map of MIT Campus showing the location of the Stata Center
..........
=:-.- :::-::::
..................
..........
4.
.A
I
It
mw.
Ln
,
raa
of
r r--4
F7i E:
0
Figure 2-2: View of MIT Stata Center building (photo courtesy Philip Greenspun)
..
...
.......
..
......
.....
.....
-1MEPLANTAKENFROM TWOOCWt PLANOf LAND.
N
TlE Or TE flOLOOMAE
MMA$OV9AU1S
AND
PN AM
J...~L
2. EWMMONSREFERTO CAMWUM MY SW
Figure 2-3: Project Plan and Adjacent Buildings Location
WW~D(ON),
Figure 2-4: Geotechnical Instrumentation Location Plan
APPROX.
LOCATION OF
SUBSURFACE PROFILES
0
Figure 2-5: Subsurface Profiles Plan
200
400
i
r ----------- I
a VAMAR-221M
I
a
ACH31MM
93
-19
-4M
ON
I
I
V'A
va
5A
I
ansr
M
SECTIONB
min
IIT
5rdpm.).
as
B.
-u
K-u
m
-I.
IN
S
k
VAoCAR*TlET
*M.
T
NAT
I
-in
am-1
N
S4
[~]
SClay
Fill
Organics
0
Sand
I Bedrock
Glacial TiLL
Figure 2-6: Subsurface Profiles A, B, and C
SECTION D
ID
W41
a.=T
Tm
c34n
RVAxC
,
,
_____
.
35
-----------
- - - - -- -
- - - - - - -
ill, I -#,Itl
II Ifill'
lifficli iillifl f11-1
IIIIIII HillIII IIIIIIIIII1111111111111111111111111
-30
1-M
1-70
- -- - - -- - - -
---- -- -
-1w
000
4WCI
E
SECTIONE
?LMJ
24
mi
"mobAemmI DMVOAT
aO
25
IN
.s
.....
....... .
Is
[] FiLt
1 Clay
0 Organics IGaciaL TilL
MBedrock
E3Sand
Figure 2-7: Subsurface Profiles D and E
.................
....
20
4:-200
-80
0
2
4
6
8
In-Situ StressPore Pressure (ksf)
Assumes Hydrostatic pwp
Figure 2-8: In-Site Stress and Pore Pressure vs. Elevation
36
10
-10.00
Su vs Elevation
0.00-20.00
-10.00-20.00-
-30.00
-30.00
-40.00
4
-
-40.00-
C0
-50.00w-
50 .00
w-60.00 -70.00-
-60.00
-80.00-90.00-
-70.00
-100.000
-80.00
0
500
1000
1500
2000
2500
3000
Shear Strength, Su (psi)
-
B-102
Profile computed using SHANSEP technique
1000
1500
2000
2500
3000
Shear Strength, Su (psf)
-
-B-101
500
P-1
P-4
P-7
P-10
-
P-2
P-5
P-8
Su (avg) P4 -
P-3
P-6
P-9
Su (avg) P5
Combined data from Cone Penetration Tests P1 to P10
Figure 2-9: Undrained Shear Strength Profile (after Olsen, 2001)
aM 70
00
Sc-!
I
I
SC-9(17
SC-a
C-
SOUTH WALL
amO57in
~
GENERA
-
40s
S
Figure 2-10: General Trends in Excavation
............
Uwsm
A "
TRENDS IN EXCAVATION
22f
2C
0
Building Surcharg
1.28ksf (E. -10fl
Sand
C'on
1'
'ri, ~
T '7 '7 ty'~'yT '7 Y 'Y'7'7'7Y~7'7TV '71'
Slab
'~
0
.Y-.
(41
Diaphragm
w
(A
Tiebaci Inclinatic i Wall
Free
Level
El. (f )Length
(0)
1
20
10
50
2
20
-1
20
3
20
-10
10
-12
-50
Wall
(2.5 ft thick)
200
150
100
50
0
Fixed jSpacingPreload
(ft) (kips)
50
5
112
50
5
128
50
128
5
Length()
(4)
-50
Figure 2-11: Typical Cross-Section of Tiebacks and Excavation (after Whittle, 2002)
-100
-100
20
0
-0
Sand
4ft Concrete Slab 9.
-241
0
Diaphragm
Wall
(2.5ft thick)
.44
Raker 2: EL. -10ft
RAer 1: EL +10ft
>)
--50
0
-100
.
.V
.
Diam eter
Raker
(1
3. 0
3. 0
1
2
-120
-50
0
Wan
Thickness (ins)
0.41
0.80
50
Spacing
(1)
25
25
Preload
(kips)
325
530
100
-- 100
150
Figure 2-12: Typical Cross-Section of Rakers and Excavation (after Whittle, 2002)
I- I.,...
................
.....
. .........................
.......
.......................
..............
....
..
.....
2 00
3 THREE-DIMENSIONAL FINITE ELEMENT
MODEL
3.1 Base Case Model Assumptions
3.1.1 Model Description
Comprehensive finite element analyses of soil-structure interaction offer a complete
framework for interpreting the spatial and temporal behavior for complex excavation support
systems (such as the Stata Center basement). These methods are based on calculation algorithms
that solve the systems of partial differential equations and are functions of multiple variables
such as stresses, strains, and constitutive model parameters (Potts et al., 2002). The Finite
Element Method (FEM) is a technique to find the solution to these systems of equations taking
into account a given geometry. The variables are combined into matrices and equilibrium is
satisfied by the systems of equations using numerical procedures using a computer program. The
Plaxis 3D 2011 program, a commercial special purpose finite element code, is used to build the
three-dimensional model and perform the analysis for this project.
The excavation for the Stata Center has a complex geometry and variety of structural
support systems which makes the project challenging to model (Figure 3-1). However, the
uniqueness of this project is that the excavation process was very well documented - it was
constantly photographed, monitored, and described in daily field logs, as well as recorded on
webcams located around the construction site. Using these data, it is possible to create a precise
three-dimensional numerical model of the actual excavation with respect to the time frame of
construction sequence.
41
All available data were gathered and carefully analyzed. The information obtained from
the project drawings (dimensions, structural elements location and coordinates) was used to
create the initial model in a CAD (Computer-Aided Design) program, AutoDesk AutoCAD 2012
Educational Version. Figure 3-2 illustrates the CAD model of the support system in the actual
scale. Using the exact dimensions, the full three-dimensional model of the diaphragm wall with
associated support system was created in Plaxis 3D 2011.
The south-west corner was selected as a reference point, so the outer horizontal
boundaries of the geometry model were Xmi=-500 ft, Xmax=881 ft, Ymn=-500 ft, Ymax=811 ft.
The equal distance of 500 ft was measured from the each side of the diaphragm wall to the model
boundaries. It has been verified by trial analyses that this distance was "far enough" and the
model boundaries did not influence the results.
3.1.2 Soil Profile
The ground surface is approximately level at El. +21 ft, and the groundwater table is in
the overlying fill at the depth of 6 ft. The soil profile of the model consists of 11 ft of fill, 6 ft of
organics, 14 ft of sand, 85 ft of marine clay, and 15 ft of glacial till. The marine clay (Boston
Blue Clay) is sub-divided into an upper overconsolidated clay crust and a lower normally
consolidated unit. The clay has low hydraulic conductivity and is modeled as an Undrained
Elastic-Plastic (EPP) material with the undrained shear strength profile which decreases from
1,600 psf to 1,300 psf at El. -55 ft, and then increases to a maximum of 1,900 psf at the bottom
of the stratum. The other layers are also represented by the EPP (Mohr-Coulomb) model.
42
The EPP (linear elastic perfectly-plastic) Mohr-Coulomb constitutive model requires two
stiffness and three strength parameters.
The stiffness parameters of the Mohr-Coulomb model are (based on soil sample tests):
* E' - Effective Young's modulus, kip/ft2
* v - Effective Poisson's ratio
The alternative stiffness parameters are (influences by E' and v):
" G - Shear modulus, kip/ft2
G=
*
Eoed
(3-1)
2(1+v)
- Oedometer modulus, kip/ft2
Eoed
(1+
)(1-2v)
(3-2)
Stiffness varying with depth is defined by a value of Eime which is the increment of
stiffness per unit of depth. The stiffness is equal to E' for any z-coordinate above zref. For any zcoordinate below Zref the stiffness is given by (z< zref):
E'(z) = E' + (Zref - z)Einc
(3-3)
The strength parameters of the Mohr-Coulomb model are (based on soil sample tests):
" Su - Undrained Shear Strength, kip/ft2
"
"
*
<p - Effective friction angle,
- Dilatancy angle,
Plaxis 3D 2011 also offers an advanced option for the input of clay layers in which the
undrained shear strength, Su, changes with depth. In order to account for the increase/decrease of
the undrained shear strength with depth the Suice value is used, which is Su per unit of depth
43
(expressed in the unit of stress per unit depth). For any z-coordinate below Zref the stiffness is
given by (z< zef):
Su(z) = Su + (Zref - z)Sugne
(3-4)
Table 3-1 summarizes the model parameters used to represent the soil profile based on
the subsurface exploration program.
3.1.3 Groundwater Conditions
Since the site surface is assumed to be mainly horizontal, the stresses initialization is
performed using Plaxis "Ko procedure" with all soil clusters activated. The boundary conditions
used in the model are the Plaxis standard boundary conditions with fixity in the horizontal plane
at the basal boundary and zero prescribed lateral displacements along the corresponding axes at
the borders. The hydraulic conditions include head-based groundwater flow boundary conditions
(head = 15ft) at the bottom and the sides of the model. The groundwater table is specified at the
elevation of 15 ft. The specific "water levels" inside the watertight diaphragm wall are
introduced for each level of excavation to model the excavation dewatering. The current analysis
assumes the steady-state groundwater seepage and uses groundwater flow calculation mode for
each phase of the model.
3.1.4 Support Systems
The diaphragm wall panels and mat foundation were modeled as plate elements; rakers
and corner bracers were represented as prestressed node-to-node anchors. The free lengths of
tiebacks were modeled using node-to-node anchors, and the embedded pile elements represented
44
the grouted part. The input parameters for all structural elements and prestress values can be
found in Tables 3-1 to 3-4.
3.1.4.1 Diaphragm Wall and Foundation Properties
The diaphragm wall is represented by three-dimensional elastic plate elements. The toe of
the diaphragm wall does not extend into the underlying rock; therefore, it is free to move within
the soil mass. The wall is 2.5 ft thick and consists of reinforced concrete. The mat foundation
consists of a reinforced concrete slab that is 4.0 ft thick and is also modeled by the plate element.
Table 3-1 summarizes the input parameters for diaphragm wall and foundation
represented as Plaxis plate elements.
3.1.4.2 Corner Bracers Properties
The corner bracing consists of 36 in diameter steel pipe struts installed at El. 10 ft and
El. -10 ft. These were pre-loaded by jacking them in place at 50% of their design load. The
details for each struts can be found in Table 2-3, including design loads, jacking loads, strut
sizes, and angle formed between the braces and the wall. Figure 3-2 also illustrates the location
of each corner bracing strut.
The wall thickness of the first level steel pipe struts is 0.38 in. The properties of the first
level corner bracing support are estimated in the following way:
As=(D - (D2 _ 2t) 2 )
=
42.523 in 2 = 0.295 ft2
(3-5)
4.176- 106 ksf
(3-6)
where:
As - cross-sectional area, in2
D - diameter, in
t - wall thickness, in
Es= 29 000 ksi
45
EA = E, As= 1.232 -106 kip
(3-7)
where:
EA - axial stiffness, per anchor in the unit of force, kip
E, - Young's modulus of steel, ksf
As - cross-sectional area, ft2
The wall thickness of the second level steel pipe struts is 0.63 in. The properties of the
second level corner bracing support are estimated in the following way:
As =
4
(D2 - (D2 - 2t)2) = 70 in 2 = 0.486 ft2
(3-8)
where:
As - cross-sectional area, in 2
D - diameter, in
t - wall thickness, in
Es = 29 000 ksi = 4.176-106 ksf
(3-9)
EA = Es As = 2.030 -106 kip
(3-10)
where:
EA - axial stiffness, per anchor in the unit of force, kip
Es - Young's modulus of steel, ksf
As - cross-sectional area, ft2
These input parameters for the corner bracing support which is represented as node-tonode anchors and their prestress values can be found in Table 3-2.
3.1.4.3 Rakers Properties
Each raker comprises a 36 in diameter steel pipe strut that supports the wall (at El. 10 ft
and El. -10 ft) and is inclined downward to a kicker block cast into the foundation slab. All
46
rakers were pre-loaded to 50% of their design load. The details for raker support can be found in
Table 2-4 and the locations for their installation is shown in Figures 2-1 and 2-2.
The properties of the first level raker support are estimated in the following way:
As =0.32 ft2
(3-11)
Es 30 000 ksi = 4.320-106 ksf
(3-12)
EA = Es As= 1.382 -106 kip
(3-13)
where:
EA - axial stiffness, per anchor in the unit of force, kip
Es - Young's modulus of steel, ksf
As - cross-sectional area, ft2
The properties of the second level raker support are estimated in the following way:
As =0.63 ft2
(3-14)
E,= 30 000 ksi = 4.320-106 ksf
(3-15)
EA = Es As= 2.722 -106 kip
(3-16)
where:
EA - axial stiffness, per anchor in the unit of force, kip
Es - Young's modulus of steel, ksf
As - cross-sectional area, ft2
These input parameters for the raker support which is represented as node-to-node
anchors and their prestress values can be found in Table 3-2.
3.1.4.4 Tieback Properties
Each tieback consists of 4, 0.6 in. diameter high strength steel tendons (270 ksi). The free
length is sheathed with a polyethylene tube material to preclude bonding in that portion. The
47
grouted anchors consist of Type I/II Portland Cement and water. The water to cement ratio of
0.49 by weight and a minimum 28 day compressive strength of 4,000 psi.
The properties of the tieback support are estimated in the following way:
As=4(
7--2)=7.85-10-3
4
ft 2
(3-17)
where:
As - cross-sectional area, ft2
D - diameter, ft
Es= 29 000 ksi = 4.176-106 ksf
EA = Es As= 32.78-10
3
(3-18)
(3-19)
kip
where:
EA - axial stiffness, per anchor in the unit of force, kip
Es - Young's modulus of steel, ksf
As - cross-sectional area, ft2
The grouted part of the tieback support is represented as an embedded pile element. In
case of failure, the first element that fails is the steel tendon. Therefore, the total bearing capacity
of the embedded pile is:
N
embedded pile -
Lpile (Ttop,max + Thotmax)
=
800 kip
(3-20)
where:
N
embedded pile
Lpile
- bearing capacity of the embedded pile element, kip
- embedded pile element length, ksf
- the skin resistance at the pile top, in force per unit pile length, kip/ft
Tbot,max - the skin resistance at the pile bottom, in force per unit pile length, kip/ft
Ttop,max
These input parameters for the tieback support which is represented as node-to-node
anchors and embedded pile elements, as well as their prestress values can be found in Tables 3-2
and 3-3.
48
3.2 Development of the Three Dimensional Model in Plaxis 3D
3.2.1 Excavation Sequence and Phases
Although many projects can be easily sub-divided into discrete phases, the construction
schedule of the Stata Center basement involved a number of concurrent activities occurring at
different parts of the site at any given time. For example, a period of time could include
excavation work, tieback installation, and corner bracing installation happening simultaneously.
It is not a trivial task to correlate this whole construction process into the distinct stages over
selected time intervals in an FE model. The first Plaxis models for this project included up to 60
phases in an attempt to correlate the complex schedule with the available data. However, after a
more detailed interpretation of the calendar plan, the base case model with only 35 staged
construction phases was chosen. Table 3-4 summarizes the actual construction phases with the
start and end dates of each field activity based on daily field reports, together with the selected
phases for the current Plaxis 3D model. The full list of Plaxis 3D phases with the time frame is
presented in Table 3-5, and the details for each phase are shown in Table 3-6.
3.2.2 Complex Geometry Design
In order to capture the three-dimensional effects of the soil and support system responses
from a non-uniform excavation process, the complex soil volumes were imported to Plaxis 3D
from a CAD program where these shapes were extruded based on the photographs and
excavation plans. Figures 3-3 and 3-4 depict the example summaries of excavation modeling for
the Phase #3 and #30 - the CAD models of the excavation progress based on the field data
corresponding to the appropriate time frame and the Plaxis 3D input/output for the same phases
are shown.
49
Figures 3-5 to 3-10 present the process of geometry design for the simple case. First, an
empty cluster is established in the CAD program (AutoDesk AutoCAD 2012 Educational
Version) based on the input coordinates. Next, the three-dimensional soil volume for the
excavation phase using the field data is created. This soil volume cluster is then subtracted from
the empty cluster using standard commands. The obtained volume element is converted into the
CAD mesh using the mesh tessellation options presented in Figure 3-8 and subdivided into
distinct elements using the "explode" command. Finally, the converted soil cluster is directly
imported into the Plaxis 3D 2011 and used in the model (Figure 3-11).
Figures 3-12 to 3-16 present the process of geometry design for the complex case when
there is a need to take into account the previous excavation volumes. Figure 3-14 shows placing
the existing soil cluster for Phase #13
into the next cluster phase. Then, both volumes are
subtracted from each other in order to get the differentiated excavation volume. Next, all soil
cluster volumes are directly imported into Plaxis 3D 2011 after several intermediate conversion
steps described previously.
A great number of soil shapes and excavation sequences were created during this project.
Some of them required extremely complicated meshes with a very large number of elements.
The base case model for the current purposes uses an optimal version of the soil volume cluster
configuration that generated a fine mesh with the total of 111 886 elements and 173 787 nodes.
50
Table 3-1: Summary of Plaxis 3D Materials Properties - Soils
Identification
Identification
Units
#
Fill
Organics
Sand
Upper Clay
Lower Clay
Glaciomarine
1
2
3
4
5
6
Soil Model
MC
MC
MC
MC
MC
MC
Drainage type
Drained
Undrained (B) Drained
Undrained (B)
Undrained (B)
Drained
number
Color
_
_
_
Top Elevation
ft
21
10
4
-10
-55
-95
y
E
kip/ft3
kip/ft2
0.1200
200.0
0.1000
400.0
0.1300
600.0
0.1170
420.0
0.1230
0.1400
920.0
7500
v (nu)
0.3000
0.3000
0.3000
0.3000
0.3000
0.3000
G
kip/ft2
76.92
153.8
230.8
161.5
353.8
2885
Eocd
kip/ft2
269.2
538.5
807.7
565.4
1238
10.10E3
SUref
kip/ft2
0.000
37.00
1.650
0.000
0.000
0
1.000
0.000
1.300
<p (phi)
0.000
35.00
0.000
45.00
Vs
ft/s
143.6
222.4
238.9
210.7
304.1
813.9
VP
ft/s
268.6
416.1
446.9
394.2
569.0
1523
Eine
kip/ft2/ft 0.000
0.000
0.000
11.11
12.00
0.000
Zref
ft
21.00
10.00
4.000
-10.00
-55.00
-95.00
Suine
Ko
kip/ft2/ft 0.000
0.5000
0.000
0.6000
k
ft/day
0.3000
0.000
0.5000
0.3000
-7.800E-3
0.8000
7.OOOE-3
0.01500
0.6000
0.3000E-3
0.000
1.000
0.03000
3.000
Table 3-2: Summary of Plaxis 3D Materials Properties - Node-to-node Anchors
Identification
Units CornerBracing1
CornerBracing2
Rakers1
Rakers2
Tiebacks
Identification number
#
1
2
3
4
5
kip
1.232E6
2.030E6
1.382E6
2.722E6
32.78E3 (per 5 ft)
Color
EA
III_65.56E3
Prestress values
kip
See Table 2-3
See Table 2-3
See Table 2-4
(per 10ft)
See Table 2-4
See Table 2-2
Table 3-3: Summary of Plaxis 3D Materials Properties - Plates
Uh
Identification
Units
Identification number
DiaphragmWall
Foundation
#
1
2
d
ft
2.500
4.000
y
Linear
kip/ft
0.1500
Yes
0.1500
E
kip/ft2
471.0E3
471.0E3
E2
kip/ft2
471.0E3
471.0E3
Color
Yes
0.1500
0.1500
G12
kip/ft2
204.8E3
204.8E3
G13
kip/ft2
204.8E3
204.8E3
G23
kip/ft2
204.8E3
204.8E3
V12
....
..
....
...
Table 3-4: Summary of Plaxis 3D Materials Properties - Embedded piles
Identification
Units
Identification number
#
Grout
Color
E
kip/ft2
1.670E6
y
Pile type
kip/ft3
0.1500
Predefined
Predefined pile type
Massive circular pile
Diameter
ft
1.640
A
ft2
2.112
I3
ft 4
0.3551
0.3551
2ft
Skin resistance
Trop,_max
Tot, max
.........
..........
kip/ft
kip/ft
Linear
20.00
20.00
Table 3-5: Calendar plan
Actual Project phases
Description
Start Date
Daphragm Wall installation
C-,'
Calendar plan
End Date
Duration
First Lewi of West Tiebacks
12/05/00
12/27/00
22 days
First Lewi of South-West Bracing
12/06/00
12/13/00
7 days
First Lewi of South Tiebacks
12/21/00
01/05/01
15 days
First Lewi of South-East Bracing
12/18/00
01/05(01
18 days
First Level of East Tiebacks
01/02/01
01/09/01
7 days
First Levl of North-West Bracing
01/06/01
01/17/01
9 days
Second Level of West Tiebacks
01/02/01
01/18101
16 days
Second Level of South Tiebacks
01/12/01
01/23/01
11 days
Second Level of East Tiebacks
01/23/01
02101/01
9 days
Second Level of South-West Bracing
01/22/01
01/29/01
7 days
Third Level of West Tiebacks
01/29/01
02/09/01
11 days
iebacks
02/02/01
02/20/01
18 days
Second Level of South-East Bracing
02/02/01
02/1&01
14 days
Third Level of South
Novmber
Third Level of East Tiebacks
02/21/01
03/26101
33 days
First Level of North-East Bracing
03/06/01
03/14/01
8 days
Second Level of North-West Bracing
04/25/01
05/01/01
6 days
Foundation slab at the center
03/03/01
04/25/01
53 days
First Level of Raker support
04/06/01
05/1501
39 days
Second Level of Raker support
05/09/01
06/01/01
23 days
Second Level of North-East Bracing
05/30/01
06/0&01
7 days
Excavation process
11/14/00
06/19/01
-219 day
January
February
March
AprlI
May
June
..
Phase #
-
--
Date
..
....
.....
.
December
July, 2000 November, 2000 -150 days-
zPhs
______
r
-#- -- )LL
_4___
C
to C
LL
____MV___M
.
Table 3-6: Full list of Plaxis 3D phases with correlated duration time
Phases
Description
Date
Duration
0) Initial
1) Surcharge
2) Wall installation
3) Exc1
4) CornerSW1
5) Exc2
6) TiebacksW1
7) Exc3
8) TiebacksSl_ElCornerSE1
9) Exc4
5-Dec-00
19-Dec-00
27-Dec-00
11-Jan-01
14-Nov-00
5-Dec-00
13-Dec-00
19-Dec-00
P
27-Dec-00
P
11-Jan-01
10) CornerNW1
P
11) Exc5
P
12) TiebacksW2
P
13) Exc6
14) CornerSW2
15) TiebacksS2
16) Exc7
17-Jan-01
29-Jan-01
Exc8
TiebacksW3
Exc9
ExclO
TiebacksS3
CornerSE2
6-Feb-01
13-Feb-01
23-Feb-01
26) CornerNE1
27)
28)
29)
30)
31)
32)
33)
34)
35)
Exc12
Exc13
Foundation
RakersN1
Exc14
CornerNW2
RakersN2
Exc15
CornerNE2
15
6
12
6-Feb-01
P
10-Feb-01
13-Feb-01
20-Feb-01
P
8
4
3
7
P
24) TiebacksE3
25) Exc1l
8
P
17) TiebacksE2
18)
19)
20)
21)
22)
23)
17-Jan-01
P
P
29-Jan-01
153
21
8
6
23-Feb-01
3
P
14-Mar-01
25-Apr-01
8-May-01
17-May-01
55
14-Mar-01
6-Apr-01
25-Apr-01
8-May-01
15-May-01
P
17-May-01
1-Jun-01
6-Jun-01
19
23
19
13
7
2
15
5
Table 3-7: Details of Plaxis 3D Model Phases
Available excavation data
Model Phase
Description
Date: December 5, 2000
Plaxis 3D phase: #3
Excavation clusters
deactivated
Maximum Excavated
Elevation=8 ft
Date: December 19, 2000
Plaxis 3D phase: #5
Excavation clusters
deactivated
Maximum Excavated
Elevation=8 ft
First Level of South-West
Bracing installed
Date: December 27, 2000
Plaxis 3D phase: #7
Excavation clusters
deactivated
Maximum Excavated
Elevation=-4 ft
First Level of West
Tiebacks installed
Date: January 11, 2001
Plaxis 3D phase: #9
Excavation clusters
deactivated
Maximum Excavated
Elevation=-4 ft
First Level of South and
East Tiebacks installed
First Level of South-East
Bracing installed
56
Table 3-7: Details of Plaxis 3D Model Phases (continue)
Actual Phase
Description
Model Phase
-0 'A
Date: January 17, 2001
Plaxis 3D phase: #13
Excavation clusters
deactivated
Maximum Excavated
Elevation- 14 ft
First Level of North-West
__________
1
4
Bracing installed
Second Level of West
Tiebacks installed
Date: January 29, 2001
Plaxis 3D phase: #16
Excavation clusters
deactivated
Maximum Excavated
Elevation=-14 ft
Second Level of South
Tiebacks installed
Date: February 6, 2001
Plaxis 3D phase: #18
Excavation clusters
deactivated
Maximum Excavated
Elevation=-14 ft
Second Level of East
Tiebacks installed
Second Level of SouthWest Bracing installed
f
Date: February 13, 2001
Plaxis 3D phase: #21
I
Excavation clusters
deactivated
Maximum Excavated
Elevation=-21 ft
Third Level of West
Tiebacks
________________________
L
57
Table 3-7: Details of Plaxis 3D Model Phases (continue)
I
Actual Phase
[
Description
Date: February 23, 2001
Plaxis 3D phase: #25
Model Phase
Excavation clusters
deactivated
Third Level of South and
East Tiebacks installed
Second Level of SouthEast Bracing installed
Date: March 14, 2001
Plaxis 3D phase: #27
Excavation clusters
deactivated
First Level of North-East
Bracing installed
4
t
Date: April 25, 2001
Plaxis 3D phase: #29
Excavation clusters
deactivated
Foundation slab installed
',A -01
4
Date: May 8, 2001
Plaxis 3D phase: #30
Excavation clusters
deactivated
First Level of Raker
support installed
Date: May 17, 2001
Plaxis 3D phase: #33
Excavation clusters
deactivated
Second Level of NorthWest Bracing installed
Second Level of Raker
support installed
58
Figure 3-1: Schematic plan of structural support system with dimensions
Figure 3-2: CAD model of the support system
59
p
a;-,i -, I kji,-
~
1641011 0.004+
Photo of excavation progress on 11/28/2000
CAD model of excavation progress on 12/05/2001
0
4100
1'
Ow
Plaxis 3D output - total ground deformations (Phase #3)
77f11111
Plaxis 3D input model (Phase #3)
Figure 3-3: Example of excavation modeling - Phase #3 (12/05/2001)
...........
-74
-b*
CAD model of excavation progress on 5/08/2001
Photo of excavation progress on 5/04/2001
I-M
1.)
Plaxis 3D output - total ground deformations (Phase #30)
Plaxis 3D input model (Phase #30)
Figure 3-4: Example of excavation modeling - Phase #30 (5/08/2001)
..............
-
o.a
Egio d
o
Solid~dtig-
Mesh
Mod.g"
-
% G+
Mody
Da-
04A
L Sctio .
-
0wo
.
smO
It
M,
-2D
4
SA
C
Figure 3-5: CAD Model (simple case) - creation of full cluster
>
P-'
M.d 9 .
-
F
SoidEdding
J
" eV
r
()CO
Modfy
5.tdio
e
"
C
-eninates
WIdU.
-
5e
iLnf a tByLo
10740
,go=62
Figure 3-6: CAD Model (simple case) - creation of input cluster based on available
information
62
Q
00
Cyr-
P
Th.,k.,5
Edge TapeFas
F4k
w
Sh..
Suten
t
M-'e
GenO
R-k.
Sph-
Sww
PIk.4-
I-II(-4-Vi-]ICOW..f"...I
; sunnue
PBRemACTe
___
T__
r--ff_____7_Lq
Figure 3-7: CAD Model (simple case)
Mah
a
C...t
M&.hEt
-
subtracting input cluster from full cluster
S.ctenSlre
M.sh
__
reme-so
o
--
LWO
Obs~um
w g ox]t
abin..n~
....
Figure
3-:
Mar
T
m
D.....-.
et..s
ce
Figure 3-8: CAD Model (simple case)
-
mesh tessellation settings for cluster conversion
63
sme4q
Meh
WS
Obert
b
@ More
Split Face Ct c wt to soli
(:)
& th Les
I - f~f.
smoth.,
Extrde
6 ..
Add Remv
RefineMeh
Creas Cr-s
Fce
0. CeHAl.
CO c
m0oo
Msh
Edik
Co
L sectin
NcOe
Section
rMsh
Movenm
epired
.PLan.
GenestSechen
Secton-
Secto
I
_________________________________
______________________________________________
Figure 3-9: CAD Model (simple case) - converted cluster
x
n
cJ~J~-
ib I&O 0 91
b*~d. ~
O
has.
o
- @s.-
o
Af A Mi
&98 -.
LP- Rw-
-
-
Lu-i-.. k
9 *
StA
Rm
un
.
P (§e
FptodesaemOun~dabject
whenyeuwntomddyif
o
--
n
a
ft
PP-
w w
==
t-
mer-t'ysW
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64
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4 RESULTS AND INTERPRETATION
This chapter compares the field measurements with the model predictions of wall
deflections, ground deformations, and pore pressures obtained from the three dimensional finite
element Base Case (A) analysis using MC soil model assuming undrained conditions within the
clay layer. The results are presented and interpreted. The effects of partial drainage (Case B
analysis, which incorporated the actual construction time from the calendar plan) on wall
deflections are discussed. A "curve integration" method
for evaluating the results is also
presented.
4.1 Wall Deflections
Figures 4-1 through 4-4 compare the lateral wall deflections at different stages of the
excavation for the North, East, South, and West walls at the actual location of vertical
inclinometers in the field. The inclinometers SC-01 through SC-03 are located along the North
wall. The movements of the East wall are measured by the inclinometers SC-04 and SC-05. In
addition, the inclinometers SC-06 through SC-08 are installed along the South wall, and the rest
of inclinometers, SC-09 though SC-11, measure the lateral wall deflections of the West wall.
Each predicted phase correspond to a specific date according to the construction sequence and
calendar plan (Table 3-5).
A general pattern of measured movements at the center of a wall typically correspond to
an initial cantilever movements of about 0.4-0.75 in during the excavation to the first tieback
support level, as well as 1.25 in before the first level of raker support. The movement was fully
recovered (except the North Wall) and the wall moved back during pre-stressing the first level of
bracing. After the installation of the first level support, the wall rotated at the brace during the
68
excavation progress. At the subsequent bracing, the wall kept moving laterally below the brace
location. The maximum movements (June, 2001) measured in the inclinometers range from 2.02.5 in at SC-02 (North), SC-04 (East), and SC-10 (West) to about 3.2 in at SC-07 (South). The
greatest movements were observed within the middle of a tieback supported wall while the
smallest movements were recorded by the inclinometers located closer to the corners. This is a
well-known three-dimensional effect attributed to the increased rigidity of the corner braces
combined with corner effects (Finno et al., 2005). In contrast, the North wall, supported by the
raker support, showed an opposite pattern with the smallest movements occurring at the center.
However, this observation could be attributed in part to the fact that the plan geometry of the
North wall consisted of two planes that intersect at the wall center (Figure 3-1).
Figure 4-1 summarizes wall deflections measured by two inclinometers located along the
East wall versus the predictions from the Base Case (A) analysis at the corresponding location
and time. The location of inclinometers on the site plan with dimensions is also shown. For the
inclinometer SC-04 located in the middle of the wall, the analysis shows a reasonable agreement
with the measured wall deflections, except the initial cantilever movement which is
underestimated by 0.5 in possibly due to the simplifications in the initial excavation geometry.
At the Phase #29, which corresponds to the installation of the foundation slab, the analysis
underestimates the maximum wall deflections by 0.35 in. The final maximum movement is
underestimated by 0.25 in during the last phase #35 corresponding to the date of 6/16/2001. The
model predictions show more movement of the top of the wall than the field measurement with
the maximum difference of 0.4 in. For the inclinometer SC-05 located close to the south-east
corner, the mode shape of deformation is an agreement with the measured data and shows the
effects of corner bracing support (the movements of the top of the wall are minimal and the
69
maximum deflections are less than those in the middle of the wall). The maximum wall
deflection at the Phase #21 (02/06/2001) is the same as in the measured data, but the toe
movement is overestimated by 0.5 in. The final maximum wall deflection at the last phase is also
underestimated by 0.5 in.
Figure 4-2 presents the comparison of wall deflections measured by inclinometers located
along the South wall and the model predictions. The MIT Alumni swimming pool building is
located 5 ft from the edge of the excavation at this location and is simulated as a threedimensional surface surcharge (1.28 ksf) at the level of the pile tip (El. -10 ft). The inclinometer
SC-07 located in the middle of the wall recorded the maximum wall deflection of 3.2 inches; the
phase #35 predictions for the same location show 2.9 in. The predictions for the inclinometer
SC-06 show a very good agreement with the measured data until the "installation of foundation
slab" phase. The field data indicate the further movement of 0.5 in at that location. The
maximum wall deflections at the location of inclinometer SC-08 are slightly overestimated by
0.2 in and the movements of the top of the wall are overestimated by 0.35 in.
Wall deflections measured by inclinometers SC-09 through SC-Il along the West wall
versus three-dimensional finite element analysis predictions are summarized in Figure 4-3. The
general wall behavior is similar to that of the east wall. The noticeable three-dimensional effects
that cause the induced ground deformations to be smaller near the corner of an excavation wall
than near its center (Finno et al., 2005) were also observed in the measured data and captured by
the analysis. The inclinometers SC-09 and SC- 11 show an excellent agreement between
measured and predicted movements. The maximum wall deflections match perfectly, but the top
and toe movements are overestimated by 0.3-0.6 in. The predicted maximum wall deflections in
the middle of the wall are reasonably consistent with the data.
70
Figure 4-4 presents the results for the North wall supported by the raker support system.
The measured data in inclinometers SC-01, SC-02, and SC-03 show perfect correlation with the
predicted data when small movements at the toe of the wall were observed at the early phases of
the analysis. However, the analysis greatly underestimates wall deflections as soon as the only
narrow soil berm was left in place before the first level raker brace installation along the north
wall. The predictions overestimate toe movements of wall by 0.5-0.6 in while underestimating
the maximum wall deflection by the same amount at the corner locations. The values of
maximum wall deflection in the middle of the North wall are 2.0 in for both measured and
predicted data.
Figures 4-5 through 4-17 show the view of excavation progress with corresponding
Plaxis model, three-dimensional wall deflections, and total ground deformations during each of
the construction phases. The three-dimensional effects of corner bracing support and effects of
the North Wall geometry can be seen from the total three-dimensional deformations of the wall.
In order to quantitatively assess the obtained predictions from the Base Case (A) model
and consistently compare them with the field data, a "curve integration" method was used. The
idea of this method is to obtain and compare the areas under each curves on the "elevation vs.
wall deflection" plots (Bolton, et al., 2010). Inclusive areas (areas broken by missing values) are
used to compare the bending moments. The total area ratio is used as a general comparison
criteria which takes into account discrepancies in both the mode shape of the wall (magnitudes of
bending) and movements of top and bottom. Figures 4-18 to 4-21 summarize the results of this
wall deflections comparison technique for the centers of the North, East, South, and West walls
of the MIT Stata Center project. It is clear that the Base Case (A) analysis underestimates the
71
magnitudes of wall bending and slightly overestimates the toe movements during the final phases
of excavation. These results can be attributed to the following possible factors:
1. The Base Case analysis assumes a constant height of the diaphragm wall with the
top at the ground surface (El. +21 ft) while the actual top elevation varied from
El. 15.4 ft to El. 19.0 ft.
2. The material properties of the diaphragm wall are assumed to be linear-isotropic.
3. The soil layers in geological profile are assumed to be horizontal. A simple
elastic-perfectly plastic constitutive soil model is used.
4. The groundwater table is assumed to be at El. +15 ft around the excavation site
and is lowered inside the impermeable diaphragm wall each time to match the
current maximum level of excavation and produce steady-state seepage.
5. The adjacent Building 57 is simulated only as a surcharge load at the tip of the
caissons.
Nevertheless, the results show on average 93% in total and 76% in inclusive areas
agreement with the measured data (integrated wall deflection curves). This is a reasonably good
agreement taking into account the usage of a relatively simple soil model.
4.2 Pore Pressures
Figure 4-22 summarizes the predicted piezometric elevations at the coordinates of the
field piezometer PZ-1 located at the center of the excavation. The excavation progress level
according to the project time frame is also present in the figure. The predicted piezometric heads
at the El. -30 ft and El. -50 ft (clay layers) show a reasonable agreement with the measured data.
However, unlike the measured data, the predicted piezometric elevation within El. -98 remain
72
almost constant throughout the time frame of excavation. This can be explained by the fact that
the model assumes undrained conditions in the lower clay adjacent to a highly permeable
material (glacial till, drained).
Figure 4-23 presents piezometric elevations measured by the piezometer PZ-2 located at
the South wall versus the Base Case (A) analysis predictions. The predictions for El. -30 are in
reasonably good agreement with the observed piezometric head. For the next elevation at El. -50,
the analysis overestimates the change in piezometric elevation. In contrast, at El. -90, the
predictions underestimate the change in piezometric elevations. One of the possible causes of
this discrepancy could be the fact that the MIT Alumni pool building is located at this exact
location which is modeled as a surcharge load.
The predictions of piezometric elevations at the location of the piezometer PZ-3 near the
North wall and measured values are compared in Figure 4-24. The predicted results for El. -50
are in very good agreement with the measured data. Nonetheless, the measured piezometric
elevation at El. -95 remain approximately constant throughout the time frame of excavation, but
the predicted values show significant changes in pore pressures at the later excavation stages.
The measured constant piezometric head can be attributed to the existence of a highly permeable
glacial till layer below the Boston Blue Clay at the corresponding elevation. Therefore, the
discrepancy in the piezometric heads can be explained by the fact that the Base Case model
assumes the bottom elevation of the clay layer still to be at El. -95 ft.
Figures 4-25 and 4-26 present the predicted and measured values of piezometric
elevations at the vicinity of the East and West walls. The predicted changes in pore pressure well
73
correspond to the excavation progress. Overall, the changes in pore pressure at these locations
are in reasonably good agreement with the field measurements.
4.3 Excavation Heave
The vertical movements of the ground and the excavation heave were monitored at
several locations during the excavation using the borehole magnet extensometers (EXT-1 to
EXT-5) located every 10 to 20 feet vertically within the marine clay stratum. A summary of the
predicted and observed vertical ground movements are shown in Figures 4-26 to 4-36.
The extensometers EXT-1 and EXT-2 were located within the excavation at the center
and 40 ft apart from the south wall. The total observed heave recorded at the extensometer EXT2 during the period from the start of excavation to mat foundation placement was about 1.4 in (at
El. -31). The model prediction shows approximately the same heave at the location of EXT-2
(Figures 4-30 and 4-31). The heave value of around 0.7-1.0 in was measured by the extensometer
EXT-1 located at the center of excavation. The analysis results are also in a relatively good
agreement with this data (Figures 4-27 and 4-28). It was reported that the observed heave within
the Boston Blue clay stratum decreased with depth below the base of the excavation and
practically stopped after mat placement. This behavior was also well captured by the model
predictions.
The magnet extensometers EXT-3, EXT-4, and EXT-5 were installed outside of the
excavation perimeter adjacent to the North, East, and West walls, respectively. The predictions
for the extensometer EXT-3 at El. +10, 0, and -20 underestimate vertical movements by 0.5 to
1.2 in. However, for the lower elevations, the numerical predictions were in agreement with the
measured values (Figure 4-32). The results for the location of the extensometers EXT-4 and
74
EXT-5 are similar and reasonably consistent with the field measurements, as can be seen in
Figures 4-33 to 4-36. The discrepancies can be explained by the usage of simplified soil
stratigraphy and limitations of the used simple soil model.
4.4 Surface Settlements
The settlements of adjacent buildings were monitored as the excavation progressed using
survey reference points (SRPs) which were attached to the buildings and installed on the Vassar
Street (behind the North Wall). Approximately 125 settlement points were optically surveyed
during the excavation work. These data were compiled into contour maps of the surface
settlement (Olsen, 2001) for each of the four sides of the excavation and compared with the
Base Case (A) model predictions (Figures 4-41 to 4-44). The largest movements on each side
were measured near the middle of each wall, where the three-dimensional model predicted the
largest wall deflections.
Figures 4-37 through 4-40 present the three-dimensional finite element analysis
predictions (Base Case A) of surface settlements behind the center of the West, East, South, and
North walls versus field measurements on June 1, 2001.
The maximum settlements at the East wall were in the order of 0.8 in, while the West
wall settlements were up to 0.9 in. These values are reasonably consistent with the results
obtained from the Base Case (A) analysis. The measured settlements at the South Wall of the
adjacent building ranged from 0.3 in to 1.8 in, and the maximum surface settlements on the
North side were about to 2 in. The analysis results underestimated the surface settlements at
these locations.
75
The Base Case (A) model also produced some amount of unrealistic heave directly
behind the selected part of the wall (Figures 4-37 to 4-40). These effects can be attributed to the
limitations of the simple constitutive model that was used in the Base Case analysis (linear
elastic perfectly-plastic Mohr Coulomb soil model).
4.5 Structural Loads
Figure 4-45 summarizes the Base Case (A) analysis predictions of tieback loads with
time along the East wall. The black color represents the first level of tieback support, the red
color symbolizes the second level of support, and the third level of tieback support is coded by
the blue color.
The error bars illustrate the standard deviation in the tieback load at a selected period of
time. Figure 4-46 presents the results for the West wall, and the tieback loads for the South wall
can be found in Figure 4-47.
4.6 Effects of Partial Drainage
The Case B consolidation analysis, which incorporated the actual construction time from
the calendar plan, was performed. Figure 4-48 summarizes the effects of partial drainage on wall
deflections in the middle of North, East, West, and South walls.
In terms of wall deflections, partial drainage caused a very small increase in the initial
cantilever wall deflections. During the subsequent phases, partial drainage caused a 0.2-0.5 in
reduction in the wall deflections. As the excavation progressed, the deflected mode shapes of the
North, East, and West walls were almost identical to the undrained analyses. However, at the
South wall location, the partial drainage analysis produced not only a reduction in the maximum
76
wall deflection, but also a reduction in the toe movement which produced more bending of the
wall. The difference between the final maximum wall deflections from the partial drainage and
the undrained analyses was about 0.5 in (Figure 4-48).
These results show that partial drainage effects do not substantially alter the excavation
performance in Boston Blue Clay, but can control the maximum wall deflections and, in some
cases, the toe movements of the diaphragm wall. Nonetheless, a partial drainage analysis requires
detailed information on permeability properties, drainage conditions, and time history of the
construction.
77
SC-04
-0.5
0.0
0.5
1.0
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SC-05
2.0
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Wall displacement (in)
Wall displacement (in)
--A
North Wall
00
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SC-04 0
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South Wall
Figure 4-1: Wall deflections measured by inclinometers SC-04 and SC-05 along the East Wall vs. 3D Finite Element Analysis
predictions (Base Case A)
..
....
......
...
SC-07
SC-06
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
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1.5
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0.5
Wall displacement (in)
Wall displacement (in)
SC-08
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
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SC-02
i
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Wall displacement (in)
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3.5
SC-07
a
SC-06
o1t
South Wall
Figure 4-2: Wall deflections measured by inclinometers SC-06 through SC-08 along the South Wall vs. 3D Finite Element
Analysis predictions (Base Case A)
SC-10
SC-09
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3,5
-0.5
0.0
0.5
1.0
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0
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0.0
0.5
1.0
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Wall displacement (in)
Wall displacement (in)
SC-11
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0.0
0.5
1.0
1.5
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2.5
3.0
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Wall displacement (in)
South Wall
Figure 4-3: Wall deflections measured by inclinometers SC-09 through SC-11 along the West Wall vs. 3D Finite Element
Analysis predictions (Base Case A)
.........
SC-02
SC-01
-0.5
204
0.0
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0.5
1.0
1.5
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2.5
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Wall displacement (in)
Figure 4-4: Wall deflections measured by inclinometers SC-01 through SC-03 along the North Wall vs. 3D Finite Element
Analysis predictions (Base Case A)
... .......
-05
SC-09
q
Excavation Progress Data - December 5, 2000
Plaxis 3D Model - Phase #3
00
tIda
3D Wall Deflections
Total Ground Deformations
Figure 4-5: Excavation Progress on December 5, 2000 and 3D Finite Element Analysis Predictions (Base Case A)
.1
....
..........
..........
:
...........
...
-os
SC-09
q
Excavation Progress Data - December 19, 2000
Plaxis 3D Model - Phase #5
00
3D Wall Deflections
Total ground deformations
Figure 4-6: Excavation Progress on December 19, 2000 and 3D Finite Element Analysis Predictions (Base Case A)
sc-o9w
p
Excavation Progress Data - December 27, 2000
Plaxis 3D Model - Phase #7
00
3D Wall Deflections
Total ground deformations
Figure 4-7: Excavation Progress on December 27, 2000 and 3D Finite Element Analysis Predictions (Base Case A)
'-05
SC-09
q
Excavation Progress Data - January 11, 2001
Plaxis 3D Model - Phase #9
00
3D Wall Deflections
Total ground deformations
Figure 4-8: Excavation Progress on January 11, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
.....
. ...............
.......
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SC-09 4
Excavation Progress Data - January 17, 2001
(10'RI
00
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Total ground deformations
Figure 4-9: Excavation Progress on January 17, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
.
.. . I ......................
..
SC-09
q
Excavation Progress Data - January 29, 2001
Plaxis 3D Model - Phase #16
000
DMM
3D Wall Deflections
Total ground deformations
Figure 4-10: Excavation Progress on January 29, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
...
....
................
....
..............
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...................
. .....
. ..
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SC-01
SC-05
SC-06
SC-1
SC-07
SC-10
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South Side
SC-09
Excavation Progress Data - February 6, 2001
Plaxis 3D Model - Phase #18
00
00Iw
3D Wall Deflections
Total ground deformations
Figure 4-11: Excavation Progress on February 6, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
-
=
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Plaxis 3D Model - Phase #21
Excavation Proaress Data - February 13, 2001
00
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3D Wall Deflections
Total ground deformations
Figure 4-12: Excavation Progress on February 13, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
......
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................
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Plaxis 3D Model - Phase #25
Excavation Progress Data - February 23, 2001
[-
11
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3D Wall Deflections
Total ground deformations
Figure 4-13: Excavation Progress on February 23, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
..........
......
....
.. ......
SC-05
Sc-o9q'
Excavation Progress Data - March 14, 2001
3D Wall Deflections
Plaxis 3D Model - Phase #27
Total ground deformations
Figure 4-14: Excavation Progress on March 14,2001 and 3D Finite Element Analysis Predictions (Base Case A)
............
I.............
.....
....
..
...
.....
SC-09 q
Excavation Progress Data - April 25, 2001
Plaxis 3D Model - Phase #29
=0
tow
I"
tn.
Mm
am
.m
am
"M
3D Wall Deflections
Total ground deformations
Figure 4-15: Excavation Progress on April 25, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
SC-09 M
Excavation Progress Data - May 8, 2001
Plaxis 3D Model - Phase #30
MGM
10
3D Wall Deflections
Total ground deformations
Figure 4-16: Excavation Progress on May 8,2001 and 3D Finite Element Analysis Predictions (Base Case A)
...
.....
..
..
...
....
........
............
SC-09 q
Excavation Progress Data - May 17, 2001
3D Wall Deflections
Plaxis 3D Model - Phase #33
Total ground deformations
Figure 4-17: Excavation Progress on May 17, 2001 and 3D Finite Element Analysis Predictions (Base Case A)
SC-02
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-0.5
3.5
0.0
0.5
1.0
SC-02
1.5
2.0
2.5
3.0
4
204
20 A
3.5
10
0
-10
-10
> -20
-20
w
-30
Measured data
-W-2/2
-40
-4-2/27
--
3/20
-s0
-4-6/16
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Wall displacement (in)
SC-02
-0.5
0.0
0.5
20 J
1.0
1.5
2.0
2.5
3.0
3.5
T
1
Simulation
0.0
....
0.5
1.0
I|
,.I
1.5
2.0
2.5
3.0
3.5
2.5
3.0
3.5
Wall displacement (in)
-1-4) ComerSW1
-4.-9) Exc4
-'W-25) Exc1 1
-4-35) ComerNE2
SC-02
-0.5
0.0
1.0
0.5
20J
10
10.
0
0.
-
-10
1 11
-0.5
'
1.5
I
2.0
I
uI
I
1
I
3.0
3.5
-10.
0
> -20
-20.
w
-30
-30.
-40
-40.
-50-|-0.5
- r
0.0
-50 |
0.5
1.0
1.5
2.0
Wall displacement (in)
2.5
3.0
3.5
-0.5
,
I
0.0
,
,
0.5
I
1.0
I
1.5
,
2.0
,
2.5
Wall displacement (in)
Figure 4-18: Wall Deflections Comparison Technique for the North Wall - Measured Data vs. Simulation (Base Case A)
.....
........
..
......................
. ...................
SC-04
-0.5
0.0
20
0.5
1.0
I
I
I
1.5
I
SC-04
2.0
I
2.5
I
3.0
3.5
I
I
-0.5
0.0
0.5
1.0
1.5
2.0
3.0
3.5
2.5
3.0
3.5
2.5
20.
10
10-
0
0-
Inclusive Area
Ratio = 91.98%
Total Area
Ratio = 93.31%
-10
-10-
-20
-20-
-30
-30-
0
(U
-I
-40
-50
-0.5
,-
0.0
'--,-,
0.5
1.0
,
1.5
I
2.0
I
2.5
3.5
3.0
Wall displacement (in)
-0.5
0.0
0.5
1.0
SC-04
1.5
Measured data
-50
-y- 3/20
-4-4/25
-0.5
0.0
1.0
0.5
2.5
3.5
3.0
20-
2.0
Sc-04
-0.5
EAL. 3
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1.0
1.5
2.0
2.5
3.0
3.5
20-
-4-16) Exc7
-y-27) Exc12
-4-29)Foundation
Inclusive Area
Ratio = 50.97%
1.5
Wall displacement (in)
Simulation
2.0
7
10-
-40
-0-1117
-AP-2/2
10-
0
0Total Area
Ratio =96.61%
j.10
-20
-20-
-30-
-30-
-40-
-40-
Inclusive Area
Ratio = 61.18%
w
-50,
Total Area
Ratio = 98.74%
-50U.5 0.0
0
1.0
1.5
2.0lZn
(n.)
-0.5
13.5
0.0
0.5
Wall displacement (in)
Wall displacement (in)
Figure 4-19: Wall Deflections Comparison Technique for the East Wall - Measured Data vs. Simulation (Base Case A)
...
................
..
....
............
.............
-0. 5
0.0
0.5
1.0
SC-07
SC-07
1.5
2.0
2.5
3.5
3.0
-0.5
20-
1.0
0.5
0.0
1.5
2.0
2.5
3.0
3.5
20-
10-
Inclusive Area
Ratio = 65.28%
10-
0-
Inclusive Area
Ratio = 91.88%
-10-
Total Area
Ratio = 99.07%
0-
E.
-
C
-10-
2
-20-
(U -20-
w
w
-30-
-6-1/26
2/6
-4-3/2
-40-
-,;n I
-0.5
'
00
0.5
1.0
1.5
2.0
2.5
3.0
3.5
C
0.0
0.5
1.0
1.5
2.0
Total Area
Ratio = 98.80%
-40
4-3/12
-0.5
0.0
2.5
3.5
3.0
20 T
-&-13) Exc6
-y-21) ExcO
2.5
3.0
3.5
2.0
2.5
3.0
3.5
2.0
2.5
3.0
3.5
2.0
SC-07
-0.5
Excl2
-- p-29) Foundation
-4-27)
0.0
2010-
0
0C
0
1.5
Wall displacement (in)
10
-10
10
0.5
Simulation
Wall displacement (in)
SC-07
-0.5
-30-
Measured data
-10
.0
-20
-20-
0.5
i
1.0
-
.
1.5
.%
Inclusive Area
Ratio = 67.69%
Total Area
Ratio = 95.38%
w
-30
-30-
-40
-40 -
-50--0.5
,
0.0
0.5
1.0
1.5
.
V
2.0
Wall displacement (in)
-50
I
.
2.5
3.0
3.5
0.0
0.5
1.0
1.5
Wall displacement (in)
Figure 4-20: Wall Deflections Comparison Technique for the South Wall - Measured Data vs. Simulation (Base Case A)
.......
.........
.......
....
...
..................................................
................
. .......
SC-10
-0.5
0.0
0.5
1.0
SC-10
2.0
2.5
3.0
-0.5
3.5
20-
20-
10-
10-
Inclusive Area
Ratio = 96.20%
0
C
1.5
-10 -
1.5
2.0
2.5
3.0
3.5
Inclusive Area
Ratio = 95.45%
-10-
Total Area
Ratio = 89.82%
-20-
-20-
w
w
-30-
-30-
Measured data
-0-1/17
-40-50-
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
-0.5
0.0
0.5
1.0
1.5
2.0
-1/24
-7--2/16
-4-3/2
2.5
3.0
3.5
-50-
-0.5
0.0
0.5
Inclusive Area
Ratio = 73.88%
1.0
1.5
2.0
2.5
3.0
Wall displacement (in)
-4-7) Exc3
-6--16) Exc7
-y--25) Excil
-4-29) Foundation
2010-
-40
Simulation
Wall displacement (in)
SC-10
o00
1.0
0.5
0-
Total Area
Ratio =82.73%
0
0.0
SC-10
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1.0
1.5
2.0
2.5
3.0
3.5
20
10
0-
0
-10-
-10
> -20-
-20
.2
-30-
Total Area
Ratio = 90.52%
-50
-0.5
0.0
0.5
1.0
1.5
2.0
Wall displacement (in)
2.5
3.0
150
-40
3.5
-5C
-0.5
Inclusive Area
Ratio = 76.04%
Total Area
Ratio = 93.67%
0.0
0.5
Wall displacement (in)
Figure 4-21: Wall Deflections Comparison Technique for the West Wall - Measured Data vs. Simulation (Base Case A)
Piezometric Elevation at PZ-1
20-
A
A AA
A
A
A
A
AA
104)
o
E
0
0-10-20-30-40
a. -50
Nov
Dec
Jan
Feb
Mar
May
Apr
Jun
Jul
Excavation Level
a Predicted PZI-1 (El. -30)
20-
*
A
10
-
0
4"
Predicted PZI-2 (El. -50)
Predicted PZI-3 (El. -98)
0-10
Measured PZ1-1 (El. -30)
---
Measured PZ1 -2 (El. -50)
Measured PZ1-3 (El. -98)
-
-20-
Nov
Dec
Ja Ir
Jan
F
Feb
I
Mar
Apr
May
Jun
Jul
North Wall
PZ-1, EXT-1
w
South Wall
Figure 4-22: Piezometric elevations measured by PZ-1 vs. 3D Finite Element Analysis
predictions (Base Case A)
99
Piezometric Elevation at PZ-2
20
*
10
()
0
r
-10
.)
-20
-30
E
*
a
A
0 -40
a.
0e
A
-50
Nov
Jan
Dec
Feb
Mar
May
Apr
A
AA
Jun
Jul
Excavation Level
20
10
0
m Predicted PZ2-1 (El. -30)
-
*
A
-
-- Measured PZ2-1 (El. -30)
-- Measured PZ2-2 (El. -50)
-- Measured PZ2-3 (El. -90)
0-
4) -10
M
Predicted PZ2-2 (El. -50)
Predicted PZ2-3 (El. -90)
-
-20NovI
Nov
D
Dec
I
I
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
4.'
4.'
0)
a)
w
PZ-2, EXT-2
South Wall
Figure 4-23: Piezometric elevations measured by PZ-2 vs. 3D Finite Element Analysis
predictions (Base Case A)
100
Piezometric Elevation at PZ-3
20 10-
a
*E&a
p
0-10-
*
-20"E -30N -40
0
C)
E -50
0
N
-60
U U
0
0
-
Ju
-I
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Excavation Level
0
0
c:
4)
w
20
-
10
-
" Predicted PZ3-1 (El. -50)
" Predicted PZ3-2 (El. -95)
0-
-10-
-
--
Measured PZ3-1 (El. -50)
Measured PZ3-2 (El. -95)
-20]
Nov
Dec
Jan
Feb
Mar
IAI
Apr
J
I
May
Jun
Jul
North Wall
0
PZ-3, EXT-3
SuhUW
South Wall
Figure 4-24: Piezometric elevations measured by PZ-3 vs. 3D Finite Element Analysis
predictions (Base Case A)
101
Piezometric Elevation at PZ-4
2010
0U
.5
-10-
0 -20-300)
fa-
-40
-50-Nov
-r-
-r
Dec
-r--r-r
Jan
-
r-~r
r-'
Feb
-r--rj--r
-i--~-
Mar
Apr
~
May
Jun
Jul
Excavation Level
0
-W
0)
W
20
-
10
-
*
*
Predicted PZ4-1 (El. -43)
Predicted PZ4-2 (El. -85)
I
-- Measured PZ4-1 (El. -43)
-- Measured PZ4-2 (El. -85)
0-
-10
-
-20Nov
I
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
PZ-4, EXT-4
0
w
South Wall
Figure 4-25: Piezometric elevations measured by PZ-4 vs. 3D Finite Element Analysis
predictions (Base Case A)
102
Piezometric Elevation at PZ-5
2010
Cu
0
0 -10-
.2 -20
E -30
0
N -40N
0)
CL -50_ _
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Excavation Level
20
-
100
Predicted PZ5-1 (El. -50)
*
Predicted PZ5-2 (El. -107)
I
Measured PZ5-1 (El. -50)
0-
--
1
.g)
Mu -10
*
Measured PZ5-2 (El. -107)
1
-
-20-
I
Nov
D
Dec
FIII
Jan
I
bI
Feb
Mar
Apr
May
Jun
Jul
North Wall
@
PZ-5, EXT-5
South Wall
Figure 4-26: Piezometric elevations measured by PZ-5 vs. 3D Finite Element Analysis
predictions (Base Case A)
103
Magnet Extensometer EXT-1
1.51.0
0.5-
A
A
A
A
0.0-
E
0
-0.5-1.0
-1.5-
-2.0
Nov
D
J
Dec
Jan
ebII
I
Feb
Mar
Apr
May
Jun
Jul
Excavation Level
0c
20
-
10
-
A
-,
4) -10
Measured (El. -28)
Measured (El. -38)
Measured (El. -49)
---
0-
-
-
Predicted (El. -28)
Predicted (El. -38)
Predicted (El. -49)
M
-20N
Nov
D
J
Feb
Dec
Jan
Feb
I
.
Mar
Apr
Ipr
I
J
May
Jun
Jul
North Wall
i
4.'
w
South Wall
Figure 4-27: Vertical Ground Movements measured by EXT-1 (upper level) vs. 3D Finite
Element Analysis predictions (Base Case A)
104
Magnet Extensometer EXT-1
1.51.0
-
0.50.0
-
E -0.5
-
4)'
0
0
-1.0-1.5
-
-2.0 |r
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Excavation Level
20
4=
0
W
.w
=U
Predicted (El. -58)
0
Predicted (El. -68)
Predicted (El. -98)
A
10
-
Measured (El. -58)
-
0-
Measured (El. -68)
Measured (El. -98)
-
--
-10
-
M
-20[
Nov
D
J
Fe
Dec
Jan
Feb
I
I
I
Mar
I
Apr
I
May
Jun
Jul
North Wall
PZ-1, EXT-1
South Wall
Figure 4-28: Vertical Ground Movements measured by EXT-i (lower level) vs. 3D Finite
Element Analysis predictions (Base Case A)
105
Magnet Extensometer EXT-2
1.51.0
0.5
0.0
W)
E -0.5
0
-1.0
-1.5-2.0 Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Excavation Level
Predicted (El. -31)
20~
Predicted (El. -51)
A
Predicted (El. -61)
----
Measured (El. -31)
Measured (El. -51)
Measured (El. -61)
100
(D
>D
0-10_
-20Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
PZ-2, EXT-2
South Wall
Figure 4-29: Vertical Ground Movements measured by EXT-2 (upper level) vs. 3D Finite
Element Analysis predictions (Base Case A)
106
Magnet Extensometer EXT-2
1.51.00.50.0E
-0.5-
0
E -1.0
-1.5 -201-1
Nov
Dec
Jan
Feb
Mar
Apr
I
I
May
Jun
Jul
Excavation Level
0
co
20
-
10
-
*
*
0-
Predicted (El. -70)
Predicted (El. -100)
-
Measured (El. -70)
-
Measured (El. -100)
-10-20Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
Cto
PZ-2, EXT-2
South Wall
Figure 4-30: Vertical Ground Movements measured by EXT-2 (lower level) vs. 3D Finite
Element Analysis predictions (Base Case A)
107
Magnet Extensometer EXT-3
1.51.0
-
0.5-
0.0
-
E
-0.5-
0
0
-1.0-
A
6
-1.5-20A
-I
Nov
Dec
Jan
Feb
I
I
Mar
Apr
May
Jun
Jul
Excavation Level
0
Cu
20
-
10
A
Predicted (El. 10)
Predicted (El. 0)
Predicted (El. -20)
--
Measured (El. 10)
Measured (El. 0)
0-
-10
-
III
-
Measured (El. -20)
-20-
Nov
Dec
Jan
Feb
Mar
Apr
May
unI
Jul
North Wall
PZ-3, EXT-3
South Wall
Figure 4-31: Vertical Ground Movements measured by EXT-3 (upper level) vs. 3D Finite
Element Analysis predictions (Base Case A)
108
Magnet Extensomneter EXT-3
1.5
-
1.00.5-
E
0
0.0
-
-0.5
-
-1.0
-
-1.5-2~O
I
i1
I
Dec
I
Dec
Nov
Jan
F
A
A
A
M
I
Feb
Mar
Apr
May
Jun
Jul
May
Jun
Jul
Excavation Level
20-
10
-
A
0
4-I
0--
-10
-
-
-20-
Nov
Predicted (El. -50)
Predicted (El. -60)
Predicted (El. -90)
Measured (El. -50)
Measured (El. -60)
Measured (El. -90)
Dec
Jan
Feb
Mar
Apr
North Wall
PZ-3, EXT-3
a)
Sot)aU)
Mu
South Wall
Figure 4-32: Vertical Ground Movements measured by EXT-3 (lower level) vs. 3D Finite
Element Analysis predictions (Base Case A)
109
Magnet Extensometer EXT-4
1.51.0
0.50.0W
E
-0.5
0
0
-1.0
-1.5
-2.0
Nov
Dec
Jan
Feb
Mar
Apr
May
Excavation Level
20
-
10
-
A
0
Jun
Jul
Predicted (El. 9)
Predicted (El. -3)
Predicted (El. -11)
Measured (El. 9)
Measured (El. -3)
0-
Measured (El. -11)
(D -10
0.
>w
-
-20-
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
PZ-4, EXT-4
0
South Wall
Figure 4-33: Vertical Ground Movements measured by EXT-4 (upper level) vs. 3D Finite
Element Analysis predictions (Base Case A)
110
Magnet Extensometer EXT-4
1.51.0
0.5
C
0.0-
A
a)
A
E -0.5a) -1.0
0
-1.5-2.0
-
Nov
I
Apr
Mar
Apr
FebI
Dec
Jan
Feb
I
I
May
I
Jun
Jul
Excavation Level
20
-
10
-
*
*
Predicted (El. -21)
Predicted (El. -30)
A
Predicted (El. -75)
0
0-
4.0
cc -10
Measured (El. -21)
Measured (El. -30)
Measured (El. -75)
-
-20Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
PZ-4, EXT-4
0
South Wall
Figure 4-34: Vertical Ground Movements measured by EXT-4 (lower level) vs. 3D Finite
Element Analysis predictions (Base Case A)
111
Magnet Extensometer EXT-5
1.51.0
0.50.0-
.
E -0.50
to
0
-1.0
-1.5
-2.0
Nov
Dec
Jan
Feb
Mar
Apr
May
.Ju
Jun
Jul
Excavation Level
20
A
10
0
-W
0)
95
Predicted (El. 9)
Predicted (El. -1)
Predicted (El. -21)
-- Measured (El. 9)
-- Measured (El. -1)
0-10-
Measured (El. -21)
-20Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
0
PZ-5, EXT-5
South Wall
Figure 4-35: Vertical Ground Movements measured by EXT-5 (upper level) vs. 3D Finite
Element Analysis predictions (Base Case A)
112
Magnet Extensometer EXT-5
1.5
-
1.00.5-
0.0
-
E -0.5
-
0
0
-1.0-1.5
-
1
-2.0
Nov
Dec
1
.
Jan
Feb
Mar
Apr
May
Jun
Jul
Excavation Level
20100
Predicted (El. -50)
0
A
Predicted (El. -60)
Predicted (El. -80)
---
Measured (El. -50)
Measured (El. -60)
Measured (El. -80)
-
0-
c) -10-
M
U
-20
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
North Wall
0
PZ-5, EXT-5
South Wall
Figure 4-36: Vertical Ground Movements measured by EXT-5 (lower level) vs. 3D Finite
Element Analysis predictions (Base Case A)
113
Settlements vs. Distance
East Wall (center)
0.2
0.0
-a-eA
-r-
-0.2
3
7
16
27
-4-Phase 29
eo Phase 35
0
E
Phase
Phase
Phase
Phase
Field measurements
-0.4
a)
a
(I) -0.6
-0.8
-1.0 L.
500
450
400
350
300
250
200
150
100
50
0
Distance (ft)
Figure 4-37: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the East wall vs. measured data (June 1, 2001)
114
Settlements vs. Distance
South Wall (center)
0.0
-----&-v---
-0.5
-+-
e
Phase 3
Phase 8
Phase 13
Phase 21
Phase 27
Phase 29
Phase 35
Field measurements
E -1.0
CO,
-1.5
-2.0 L-
500
450
400
350
300
250
200
150
100
50
0
Distance (ft)
Figure 4-38: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the South wall vs. measured data (June 1, 2001)
115
Settlements vs. Distance
West Wall (center)
0.2
0.0
-+-
-e-
-0.2
-q-
--
C
E
--
e
-0.4
Phase 3
Phase 7
Phase 16
Phase 25
Phase 29
Phase 35
Field measurements
O) -0.6
-0.8
-1.0 L500
450
400
350
300
250
200
150
100
50
0
Distance (ft)
Figure 4-39: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the West wall vs. measured data (June 1, 2001)
116
Settlements vs. Distance
North Wall (center)
0.0
-
Phase 4
Phase 6
Phase 9
Phase 25
Phase 30
Phase 35
9
Field measurements
-
-0.5
-
-,v-
C
(I)
E
4)
-1.0
CO
-1.5
-2.0
500
450
400
350
300
250
200
150
100
50
0
Distance (ft)
Figure 4-40: 3D Finite Element Analysis predictions (Base Case A) of surface settlements
behind the North wall vs. measured data (June 1, 2001)
117
[*10-3 ft]
0.00
-10.00
-15.00
-20.00
-25.00
-30.00
-35.00
-4.00
-45.00
oo
-50.00
-60.00
-65.00
-70.00
#
-75.00
-85.00
-W0.00
-95.00
Base Case A - Phase 34
Field data - June 1, 2001
-100.00
Figure 4-41: Settlement contours for the East wall based on compiled data from the surface settlement points (after Olsen,
2001) vs. 3D Finite Element Analysis predictions (Base Case A)
[*10- 3 ft]
0.00
-5.00
-10.00
-15.00
-20.00
-25.00
-30.00
-35.00
Field data - June 1, 2001
-40.00
45.00
-50.00
-55.00
-60.00
-65.00
-70.00
-75.00
-80.00
-85.00
-90.00
-95.00
-100.00
Base Case A - Phase 34
Figure 4-42: Settlement contours for the North wall based on compiled data from the surface settlement points (after Olsen,
2001) vs. 3D Finite Element Analysis predictions (Base Case A)
[*10- ft]
0.00
-
-5.00
-10.00
-15.00
-20.00
-25.00
-30.00
-35.00
-40.00
Field data - June 1, 2001
45.00
-50.00
-55.00
-60.00
-65.00
-70.nfl
-75.00
-80.00
-85.00
-90.00
-95.00
-100.00
Base Case A - Phase 34
Figure 4-43: Settlement contours for the North wall based on compiled data from the surface settlement points (after Olsen,
2001) vs. 3D Finite Element Analysis predictions (Base Case A)
..
....
....
......
[*10-3 ft]
0.00
-5.00
-10.00
-15.00
-20.00
-25.0
-30.00
-35.00
-40.0
45.0
-50.00
-60.00
-70-fin
-65.00
-75.00
-80.00
soo-to
-90.00
Base Case A - Phase 34
Field data - June 1, 2001
-100.00
Figure 4-44: Settlement contours for the West wall based on compiled data from the surface settlement points (after Olsen,
2001) vs. 3D Finite Element Analysis predictions (Base Case A)
.1 -
.... - .
. -
.... . .
...........
- I. .........
......
-
East Wall - Tieback Loads
31
-
3029U)
28-
J.
27-
(D,
26-
_j
CU
-J
25-
-o-e-o-
24-
23-
First Level Tiebacks
Second Level Tiebacks
Third Level Tiebacks
2221-
Dec
Jan
Feb
Mar
ArI
Ma
Jun
Apr
May
Jun
Time (months)
Figure 4-45: 3D Finite Element Analysis predictions (Base Case A) of tieback loads vs. time
along the East wall
122
West Wall - Tieback Loads
313029282726(D
25-
-e- First Level Tiebacks
-*- Second Level Tiebacks
-*-Third Level Tiebacks
.0
242322
21-
.5
De c
Jan
Feb
Mar
Apr
May
.5
Jun
Time (months)
Figure 4-46: 3D Finite Element Analysis predictions (Base Case A) of tieback loads vs. time
along the West wall
123
South Wall - Tieback Loads
31
-
302928-
27co
(D
0.
-o
26-
U
2524
-- First Level Tietbacks
-- Second Level Tiebacks
-*- Third Level Tie backs
-
-
232221-
I
Dec
Jan
Feb
Mar
Apr
May
Jun
Time (months)
Figure 4-47: 3D Finite Element Analysis predictions (Base Case A) of tieback loads vs. time
along the South wall
124
SC-02
-0.5
0.0
0.5
1.0
1.5
SC-04
2.0
2.5
3.0
20
3.5
-0.5
-
0.0
0.5
1.0
15
2.0
2.5
3.0
3.5
Undranted
Anasis
2o40'-hK(''
2
-4-91 AC4
-4-3)EW1
-ti1) Exc
-4-35) Caff*042
10-
Partial
DrakageAnalysis
0?)E
-e-4) ComrSW1
73
-.W-27)Exc12
-&-9) Exc4
0-
-9-25)Excil
-4- 35) Cwfl6(NE2
-10-
--
29)Foundation
-4- 36 CornrNE2
-10
c
> -20-
> -20
w
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Wall displacement (in)
Wall displacement (in)
SC-07
-0.5
0.0
0.5
1.0
1.5
SC-10
2.0
2.5
3.0
3.5
-0.5
Undrained
Analyrs
20
0.0
0.5
1.0
1.5
2.0
-10
-0- 7)
EaC
Partial
Drainage
Analysis
-4-27) EWr2
e
-6-29) Foundn
-4-35) Ce4.E2
.-0
3.5
-9-2S)EnII
-4-29) Found~aon
ParilaDrainag A"a"si
-6-3) Exc1
-4-8) TlbdcsS1.E1.SE1
-&-13) Exc6
-q-21) Earl
0
3.0
Undrained Analysis
13)EaS
-9-21) ExcIO
-4-27) Exc12
-- 29)Foundsbon
-0- 35) CarneaN!
10
2.5
-0--3)EarI
-4-?) Exc3
.,-,is)
Ear?
-9-25) Eacl
-4- 29)Foardawoa
-10
> -20
-20
w
-30
-40
-50
Wall displacement (in)
Wall displacement (in)
Figure 4-48: 3D Finite Element Analysis predictions-Case B (Partial Drainage Analysis) vs. Base Case A (Undrained Analysis)
5 SUMMARY AND CONCLUSIONS
5.1 Summary
The thesis demonstrated the application of the three-dimensional finite element analysis
(using a commercial Finite Element Analysis code, Plaxis 3D 2011) to the Ray and Maria Stata
Center excavation project in Cambridge, Massachusetts. This study has shown that the threedimensional finite element analysis can be effectively used for a such complex excavation
projects and is capable to achieve consistent predictions of wall deflections, ground movements,
and pore pressures for tieback, corner-braced, and raker supported diaphragm walls. The threedimensional finite element analysis results showed a good agreement with the measured data
despite of simplifications in the Base Case model.
The non-uniform ground excavation resulted in the three-dimensional effects which were
well captured in the Base Case model predictions (Figures 4-31 through 4-42). The threedimensional effects noticed in the model were similar to the effects described by Finno (2007)
where smaller ground movements occurred near the corners and larger ground movements
towards the middle of the wall due to the higher stiffness of the corner bracing system.
In order to quantitatively assess the obtained predictions from the Base Case model and
consistently compare them with the field data, a "curve integration" method was used. The
principle of this method was to obtain and compare the areas under each curves on the "elevation
vs. wall deflection" plots. The results showed on average 93% in total and 76% in inclusive areas
agreement with the measured data (integrated wall deflections curves).
The effects of partial drainage (Case B analysis, which incorporated the actual
construction time from the calendar plan) on wall deflections were also discussed. The full
126
results of the analysis and detailed directions to reproduce the Base Case model predictions were
provided.
5.2 Conclusion
This work is the first use of the fully coupled three-dimensional flow-deformation
analysis in Plaxis 3D 2011 for a such complex, well-instrumented three-dimensional case study.
The results of the analysis provided answers to the questions on the practical usage of threedimensional finite element analysis for complex excavation projects, quantitative assessment of
the three-dimensional predictions, and the effects of partial drainage on wall deflections. The
following possible explanations for some observed discrepancies in the model predictions were
given:
1. The Base Case analysis assumed a constant height of the diaphragm wall with the
top at the ground surface (El. +21 ft) while the actual top elevation varied from
El. 15.4 ft to El. 19.0 ft.
2. The material properties of the diaphragm wall were assumed to be isotropic and
linear. In reality, the reinforcement of the wall is not continuous across wall
panels; hence, bending properties are expected to be anisotropic.
3. The soil layers in geological profile were assumed to be horizontal, and a simple
elastic-perfectly plastic constitutive soil model was used.
4. The groundwater table was assumed to be at El. + 15 ft around the excavation site
and was lowered inside the impermeable diaphragm wall each time to match the
current maximum level of excavation and to produce steady-state seepage.
5. The adjacent Building 57 was simulated only as a surcharge load at the tip of the
caissons.
127
In addition, the following factors seem to have an important effect on the excavation
performance: the three-dimensional effects resulting from a non-uniform soil excavation and
corner bracing, geological profile, plan geometry of the wall, consolidation within the clay and
groundwater conditions.
Further studies using more accurate constitutive representation of the soil such as
advanced effective stress model MIT-E3 (Whittle, 1987) is recommended to assess the
importance of soil constitutive behavior on the observed field performance of the support system
for the Stata Center basement.
Although the first three-dimensional model required a great deal of time and
computational resources, with gained experience, it is now possible to construct the threedimensional models with any levels of complexity in a short amount of time. The author also
developed a program in MS Visual Basic to analyze the Plaxis 3DI output data and prepare it for
plotting automatically. Due to the size of the mesh and complex geometry, the whole model
calculation lasted almost 20 hours on a quad-core personal computer. However, with the use of
multi-core solver on a powerful machine, the computational time could be further substantially
reduced to even more practical values.
During the course of this research, a software bug in the Plaxis 3D program producing hidden excessive
lateral water loads was found and reported to the Plaxis Development Team. It helped them to identify the problem
and release a workaround solution for the previous version of Plaxis. The complete fix for the identified issue has
been implemented in the latest software update.
128
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133
APPENDIX 1
Information about the mesh
FE elements - 10-Noded
Number of soil elements - 111886
Number of nodes - 173787
..
Ow""mI D1J
f -2w-He VwwproPea
seemr
.k.n...w
Mesh
oDeomans
.tms
Toos
..- t
al
Hep
A0--
It
io~z
(6M8O0964M,0.00)
Viewpoint
(304.36, -73D32142415)
APPENDIX 2
Main input commands to rebuild the model in Plaxis 3D 2011
Wall:
surface 0 0 21 0 281 21 184 31121 381 31121 381 0 21
Corner NWI +10:
_n2nanchor 0 274
_n2nanchor 0 249
_n2nanchor 0 225
n2nanchor 0 200
10 7.144
10 32.24
10 55.11
10 80.13
Corner NW2 -10:
_n2nanchor 0 274
_n2nanchor 0 249
_n2nanchor 0 225
n2nanchor 0 200
-10
-10
-10
-10
282.2 10
286.3 10
290 10
294.1 10
7.144 282.2 -10
32.24 286.3 -10
55.11 290 -10
80.13 294.1 -10
Corner NEl +10:
_n2nanchor 381 304
_n2nanchor 381 279
_n2nanchor 381 254
n2nanchor 381 229
10 374 311
10 349 311
10 324 311
10 299 311
Corner NE2 -10:
_n2nanchor 381 304
_n2nanchor 381 279
n2nanchor 381 254
n2nanhor 381 229
-10
-10
-10
-10
374
349
324
299
311
311
311
311
10
10
10
10
-10
-10
-10
-10
Corner SWI +10:
_n2nanchor 0 7 10 7 0 10
_n2nanchor 0 32 10 32 0 10
n2nanchor 0 54 10 54 0 10
Corner SW2 -10:
_n2nanchor 0 7 -10 7 0 -10
_n2nanchor 0 32 -10 32 0 -10
n2nanchor 0 54 -10 54 0 -10
Corner SE1
_n2nanchor
n2nanchor
_n2nanchor
n2nanchor
+10:
360 0
337 0
312 0
288 0
10 381
10 381
10 381
10 381
18
43
68
90
10
10
10
10
Corner SE2
n2nanchor
n2nanchor
_n2nanchor
n2nanchor
-10:
360
337
312
288
-10
-10
-10
-10
18
43
68
90
-10
-10
-10
-10
0
0
0
0
381
381
381
381
Tiebacks WI (x12):
n2nanchor 0 70 10 -47 70 -7
embeddedpile -47 70 -7 -85 70 -21
Tiebacks W2:
n2nanchor 0 70 -1 -19 70 -8
enbeddedpile -1 9 70 -8 -66 70 -25
Tiebacks W3:
n2nanchor 0 70 -10 -10 70 -14
enbeddedpile -10 70 -14 -57 70 -31
135
Tiebacks Sl (x22):
n2nanchor 66 0 10 66 -47 -7
embeddedpile 66 -47 -7 66 -85 -21
Tiebacks S2:
n2nanchor 66 0 -1 66 -19 -8
embeddedpile 66 -19 -8 66 -66 -25
Tiebacks S3:
n2nanchor 66 0 -10 66 -10 -14
embeddedpile 66 -10 -14 66 -57 -31
Tiebacks El (x12):
n2nanchor 381 105 10 428 105 -7
embeddedpile 428 105 -7 466 105 -21
Tiebacks E2:
n2nanchor 381 105 -1 400 105 -8
embeddedpile 400 105 -8 447 105 -25
Tiebacks E3:
n2nanchor 381 105 -10 391 105 -14
embeddedpile 391 105 -14 438 105 -31
Rakers RI:
_n2nanchor
_n2nanchor
_n2nanchor
_n2nanchor
_n2nanchor
_n2nanchor
_n2nanchor
n2nanchor
124 216
144 219
163 222
183 225
203 227
228 227
253 227
278 227
Rakers R2:
_n2nanchor 114
_n2nanchor 134
n2nanchor 154
n2nanchor 173
n2nanchor 193
n2nanchor 218
n2nanchor 243
n2nanchor 268
214
217
220
224
227
227
227
227
-21 105.6 298.2 10
-21 129.5 302.1 10
-21 151.3 305.7 10
-21 176.2 309.7 10
-21 198311 10
-21 223 311 10
-21 248 311 10
-21 273 311 10
-21
-21
-21
-21
-21
-21
-21
-21
105.3 298.2 -10
129.2 302.1 -10
151.1 305.6 -10
175.9 309.7 -10
198311 -10
223311 -10
248 311 -10
273 311 -10
South Building (1.28ksf):
surfload 130 -6 -10 297 -6 -10 297 -97 -10 130 -97 -10
North Street (0.6ksf):
surfload 0 335 21 0 395 21 381 395 21 381 335 21
Foundation Slab:
surface 0 0 -21 0 150 -21 80 150 -2180 212 -21 180 228 -21282 228 -21 282 130 -21 381 130 -21381 0-21
Water Levels:
_waterlevel -500 -500
_waterlevel -500 -500
_waterlevel -500 -500
_waterlevel -500 -500
waterlevel -500 -500
15
15
15
15
15
-500
-500
-500
-500
-500
811
811
811
811
811
150 0 15 0 281 15 184 311 15 381311 15 381 0 15 881 811 15 881 -500 15
15 0 0 8 0 281 8 184 311 8 381311 8 381 0 8 881 811 15881 -500 15
15 0 0 -40 281 -4184 311 -4381 311 -43810 -4881 811 15 881 -500 15
15 0 0 -14 0 281 -14 184 311 -14 381 311 -14 3810 -14 881 811 15 881 -500 15
15 0 0 -210 281 -21 184 311 -21 381 311 -21381 0 -21 881 811 15 881 -500 15
Hydraulic Boundaries:
surfgwfbc -500 -500 -110 -500 811 -110 881 811 -110 881 -500 -110
_surfgwfbc -500 811 -110 -500 811 21 -500 -500 21 -500 -500 -110
_surfgwfbc 881 811 -110 881 811 21 881 -500 21 881 -500 -110
surfgwfbc -500 -500 21 -500 -500 -110 881 -500 -110 881 -500 21
_surfgwfbc -500 811 21 -500 811 -110 881 811 -110 881 81121
136
APPENDIX 3
The source codes of the output preparation program in Visual Basic
DEFLECTIONS - NEW FILE_IMPORT========
-=====WALL
As Integer
For ± = 1 To 33
ActiveWorkbook.Worksheets.Add After:=Sheets(Sheets.Count)
With ActiveSheet.QueryTables.Add(Connection:=
"TEXT;C: \Data\Wall deflections\SC-1l\"
& i & ".TXT",
Destination:=Range("$A$1"))
.Name = "1"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.TextFilePromptOnRefresh = False
.TextFilePlatform = 866
.TextFileStartRow = 1
.TextFileParseType = xlDelimited
.TextFileTextQualifier = xlTextQualifierDoubleQuote
.TextFileConsecutiveDelimiter = False
.TextFileTabDelimiter = True
.TextFileSemicolonDelimiter = False
.TextFileCommaDelimiter = False
.TextFileSpaceDelimiter = False
.TextFileColumnDataTypes = Array(1, 1, 1, 1, 1, 1, 1, 1, 1)
.TextFileTrailingMinusNumbers = True
.Refresh BackgroundQuery:=False
End With
Columns("A:I").Select
Range("Il").Activate
Selection.NumberFormat = "0.000000"
Selection.ColumnWidth = 15
Next i
=======/WALL DEFLECTIONS - NEW FILEIMPORT=========
Dim i
=======INCLINOMETER-north====================
Dim i As Integer
For i = 1 To 33
Windows("1.xlsx").Activate
Sheets("Sheet" & i).Select
Range("K2") .Select
ActiveCell.FormulaRlCl = "=RC[-4]* (-12)"
Range("K2").Select
Selection.AutoFill Destination:=Range("K2:K66"),
Range("K2:K66").Select
Selection.Copy
Windows("WallDisplacernents.xlsx") .Activate
137
Type:=xlFillDefault
Sheets("SC-1").Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone,
:=False, Transpose:=False
Next i
.
-======/INCLINOMETER-north-====
SkipBlanks
-=====INCLINOMETER-east==========================
Dim i As Integer
For i = 1 To 33
Windows("4.xisx").Activate
Sheets("Sheet" & i).Select
Range("K2").Select
ActiveCell.FormulaRlCl = "=RC[-5]* (-12)"
Range("K2").Select
Selection.AutoFill Destination:=Range("K2:K83"), Type:=xlFillDefault
Range("K2:K83").Select
Selection.Copy
Windows("WallDisplacements.xlsx").Activate
Sheets("SC-4") .Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks
:=False, Transpose:=False
Next i
=======/INCLINOMETER-east=============--------=======INCLINOMETER-south========================
Dim i As Integer
For i = 1 To 33
Windows("6.xlsx").Activate
Sheets("Sheet" & i).Select
Range("K2").Select
4
(12)
ActiveCell.FormulaRlCl = "
Range("K2").Select
Selection.AutoFill Destination:=Range("K2:K71"), Type:=xlFillDefault
Range("K2:K71").Select
Selection.Copy
Windows("WallDisplacenents.xlsx").Activate
Sheets("SC-6") .Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks
:=False, Transpose:=False
Next i
========/INCLINOMETER-south===-==================
-=======INCLINOMETER-west=======================
Dim i As Integer
For i = 1 To 33
Windows("9.xlsx").Activate
Sheets("Sheet" & i).Select
Range("K2").Select
(12)"
ActiveCell.FormulaRlCl = "=RC[-5
Range("K2").Select
Selection.AutoFill Destination:=Range("K2:K61"),
Range("K2:K61").Select
Selection.Copy
138
Type:=xlFillDefault
Windows("WallDisplacements.xlsx").Activate
Sheets("SC-9") .Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone,
:=False, Transpose:=False
Next i
============-=/INCLINOMETER-west================
===========PORE PRESSURES - NEWFILEIMPORT==
Dim i As Integer
For i = 1 To 33
ActiveWorkbook.Worksheets.Add After:=Sheets(Sheets.Count)
With ActiveSheet.QueryTables.Add(Connection:=
"TEXT;C:\PredictedData\2) Pore Pressures\PZ-5\"
& i & ".TXT",
Destination:=Range("$A$1"))
.Name = "1"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.TextFilePromptOnRefresh = False
.TextFilePlatform = 866
.TextFileStartRow = 1
.TextFileParseType = xlDelimited
.TextFileTextQualifier = xlTextQualifierDoubleQuote
.TextFileConsecutiveDelimiter = False
.TextFileTabDelimiter = True
.TextFileSemicolonDelimiter = False
.TextFileCommaDelimiter = False
.TextFileSpaceDelimiter = False
.TextFileColumnDataTypes = Array(1, 1, 1, 1, 1, 1)
.TextFileTrailingMinusNumbers = True
.Refresh BackgroundQuery:=False
End With
Cells.Select
Selection.ColumnWidth = 15
Selection.NumberFormat = "0.000000"
Next i
-======/PORE
PRESSURES -
NEWFILEIMPORT======
Dim i As Integer
For i = 1 To 33
Windows("PZ-1.xlsx").Activate
Sheets("Sheet" & i).Select
Range("F2,F8,F22").Select
Selection.Copy
Windows("PorePressures.xlsx") .Activate
Sheets("PZ-1").Select
139
SkipBlanks
ActiveCell.Offset(1, 0).Select
Selection.PasteSpecial Paste:=xlPasteAll, Operation:=xlNone, SkipBlanks:=
False, Transpose:=True
Next i
Dim i As Integer
For i = 1 To 33
Windows("PZ--2.xlsx").Activate
Sheets("Sheet" & i).Select
Range("F2,F17,F28").Select
Selection.Copy
Windows("PorePressures.xlsx").Activate
Sheets("PZ-2").Select
ActiveCell.Offset(1, 0).Select
Selection.PasteSpecial Paste:=xlPasteAll,
False, Transpose:=True
Next i
Operation:=xlNone, SkipBlanks:=
===========EXTENSOMETERS - NEWFILEIMPORT===
Dim i As Integer
For i = 1 To 33
ActiveWorkbook.Worksheets.Add After:=Sheets(Sheets.Count)
With ActiveSheet.QueryTables.Add(Connection:=
"TEXT;C: \PredictedData\3)Extensometers\EXT-1-lr
& i & ".TXT",
Destination:=Range("$A$1"))
.Name = "1"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.TextFilePromptOnRefresh = False
.TextFilePlatform = 866
.TextFileStartRow = 1
.TextFileParseType = xlDelimited
.TextFileTextQualifier = xlTextQualifierDoubleQuote
.TextFileConsecutiveDelimiter = False
.TextFileTabDelimiter = True
.TextFileSemicolonDelimiter = False
.TextFileCommaDelimiter = False
.TextFileSpaceDelimiter = False
.TextFileColumnDataTypes = Array(1, 1, 1, 1, 1, 1)
.TextFileTrailingMinusNumbers = True
.Refresh BackgroundQuery:=False
End With
Cells.Select
Selection.ColumnWidth = 15
Selection.NumberFormat = "0.000000"
140
Next i
===========/EXTENSOMETERS
- NEWFILEIMPORT===========
Dim i As Integer
For i = 1 To 33
Windows("EXT-1-1.xlsx").Activate
Sheets("Sheet" & i).Select
Range("F2,F3,F6,F10 ") .Select
Selection.Copy
Windows("Heave.xlsx").Activate
Sheets("EXT-1-1").Select
ActiveCell.Offset(1, 0).Select
Selection.PasteSpecial Paste:=xlPasteAll,
False, Transpose:=True
Next i
==== ===
=== ====
=== ===
Operation:=xlNone, SkipBlanks:=
/EXT= = = = = = = = = = = = =
========================EXT-1-2====
Dim i As Integer
For i = 1 To 33
Windows("EXT--1-2.xlsx").Activate
Sheets("Sheet" & i).Select
Range("F2,F13") .Select
Selection.Copy
Windows("Heave.xlsx").Activate
Sheets("EXT-1-2").Select
ActiveCell.Offset(1, 0).Select
Selection.PasteSpecial Paste:=xlPasteAll, Operation:=xlNone, SkipBlanks:=
False, Transpose:=True
Next i
==== ===
=== ====
===
===
/EXT==
= = = = = = = = = = = =
-=======SETLLEMENTS
- NEWFILEIMPORT===================
Dim i As Integer
For i = 1 To 33
ActiveWorkbook.Worksheets.Add After:=Sheets(Sheets.Count)
With ActiveSheet.QueryTables.Add(Connection:=
"TEXT;C:\PredictedData\4) Settlements\East\" &
i & ".TXT",
Destination:=Range("$A$1"))
.Name = "1"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.TextFilePromptOnRefresh = False
.TextFilePlatform = 866
.TextFileStartRow = 1
.TextFileParseType = xlDelimited
141
.TextFileTextQualifier = xlTextQualifierDoubleQuote
.TextFileConsecutiveDelimiter = False
.TextFileTabDelimiter = True
.TextFileSemicolonDelimiter = False
.TextFileCommaDelimiter = False
.TextFileSpaceDelimiter = False
.TextFileColumnDataTypes = Array(1, 1, 1, 1, 1, 1)
.TextFileTrailingMinusNumbers = True
.Refresh BackgroundQuery:=False
End With
Cells.Select
Selection.ColumnWidth = 15
Selection.NumberFormat = "0.000000"
Next i
============/SETLLEMENTS
- NEW_FILEIMPORT================
=-----------=======Settlements - East===============
Dim i As Integer
For i = 1 To 33
Windows("East.xlsx").Activate
Sheets("Sheet" & i).Select
Range("H2").Select
ActiveCell.FormulaRlCl = "RC[-51-381"
Selection.AutoFill Destination:=Range("H2:H85"), Type:=xlFillDefault
Range("I2").Select
ActiveCell.FormulaRlCl = "=RC[-3]*(12)"
Range("I2").Select
Selection.AutoFill Destination:=Range("I2:I85"), Type:=xlFillDefault
Columns("I:I").Select
Selection.Copy
Windows("Surface Settlements.xlsx").Activate
Sheets("East").Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks
:=False, Transpose:=False
Next i
=============/E
nd=
==============-==========Settlements
- West===============
Dim i As Integer
For i = 1 To 33
Windows("West.xl sx").Activate
Sheets("Sheet" & i).Select
Range("12").Select
ActiveCell.FormulaRlCl = "=RC[-3]*(12)"
Range("12").Select
Selection.AutoFill Destination:=Range("12:I85"), Type:=xlFillDefault
Columns("I:I").Select
Selection.Copy
Windows("SurfaceSettlements.xlsx") .Activate
Sheets("West").Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks
:=False, Transpose:=False
Next i
I
qj-
142
- South===============
==========================Settlements
Dim i As Integer
For i = 1 To 33
Windows("South.xisx").Activate
Sheets("Sheet" & i).Select
Range("12").Select
ActiveCell.FormulaRlCl = "=RC[-3]* (12)"
Range("12").Select
Selection.AutoFiil Destination:=Range("I2:185"),
Columns("I:I").Select
Selection.Copy
Windows("SurfaceSettlements.xlsx").Activate
Type:=xlFillDefault
Sheets("South").Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks
:=False, Transpose:=False
Next i
=====
==== ====
====
====/West=============================-- North===----=======
======================Settlements
Dim i As Integer
For i = 1 To 33
Windows("North.xlsx").Activate
Sheets("Sheet" & i).Select
Range("H2").Select
ActiveCell.FormulaRlC1 = "=RC[-41-311"
Selection.AutoFill Destination:=Range("H2:H91"), Type:=xlFillDefault
Range("12") .Select
ActiveCell.FormulaRlCl = "=RC[-3]*
(12)"
Range("12").Select
Selection.AutoFill Destination:=Range("I2:I91"), Type:=xlFillDefault
Columns("I:I").Select
Selection.Copy
Windows("Surface Settlements.xlsx").Activate
Sheets ("North") . Select
ActiveCell.Offset(O, 1).Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks
:=False, Transpose:=False
Next i
nd
=
--
-
--
143
-==
=
=