A METHOD
TO PREDICT
PARTIALLY DRAINED
DEFORMATIONS
FOR
CONDITIONS IN BRACED
EXCAVATIONS
by
Theodore
B.S.
von
Rosenvinge
Eng. Northeastern
IV
University
(1978)
Submitted in part ial
of the requirements
fulfillment
for the
degree of
Master of Science
at
Massachusetts
the
Institute of
Technology
(August 1980)
Q
Theodore von Rosenvinge IV
Signature of Author
Department
Certified
of
Civil
Engineering,
August 14,
1980
by
Thesis
Supervisor
Accepted by
Chairman, Departmental
Students of
Committee on Graduate
the Department of
MASSACHUSETTS INSTIIUT:
OF TECH ,VOG,
OC T 9
1980
Civil Engineering.
2
A METHOD TO PREDICT
DEFORMATONS FOR
PARTIALLY DRAINED CONDITIONS IN
BRACED EXCAVATIONS
by
Theodore
von
Rosenvinge
IV
Submitted to the Department of Civil Engineering
on August 14, 1980 in partial fulfillment of the
requirements for the degree of Master of Science in
Civil Engineering
ABSTRACT
The purpose of this thesis is to develop a method to
predict deformations in braced excavations, which includes
The time
the effects of excess pore pressure dissipation.
variables considered are time for construction compared with
time required for pore pressure equilization due to altered
The method will apply the Stress
flow conditions and shear.
Path Method to determine appropriate soil parameters to use
in the existing finite element program, BRACE III in a way
that accounts for time effects.
The method will be applied to an actual case to
demonstrate its applicability and illustrate its use.
Thesis
Supervisor:
Title:
Dr.
William Allen
Research
Associate
Marr
3
To M.E.
and Marta
4
ACKNOWLEDGMENTS
The
his
author
interest
author
is
and
also
providing
is
grateful
to
Dr.
guidance during
grateful
William Allen Marr
the
to Professor
information and
soil
work on
T.W.
specimens
this
for
thesis.
The
Lambe
for
his
support,
tested
for
the
case
study.
The
author
also wishes
and
discussion provided
ern
University
Special
Marta
for
hours
on
during
thanks
humor was
tion while
her
and
of
thanks
father
to my
encouragement
to
stages
my wife,
during my
processor are
sustaining
note
Walter E.
early
due
their patience
the word
acknowledge
by Dr.
the
is
to
during
the
this
M.E.,
education.
gratefully
was working on his
family
last
for
generous
Jaworski
of
supplied by Marta's
entire
the
of
advice
Northeast-
thesis.
and
young
M.E.'s
daughter,
tireless
acknowledged.
often welcome
"thethiss".
their
continued
several years.
The
distracAnd
a
support
5
TABLE
OF CONTENTS
Page
TITLE PAGE
1
ABSTRACT
2
DEDICATION
3
ACKNOWLEDGEMENTS
4
TABLE
OF
5
CONTENTS
9
LIST
OF
TABLES
LIST
OF
FIGURES
CHAPTER ONE
10
INTRODUCTION
1.0
INTRODUCTION
14
1.1
THESIS
OBJECTIVE
19
1.2
THESIS
SCOPE
19
CHAPTER TWO
THE
ROLE OF
TIME
2.0
INTRODUCTION
21
2.1
STRESS
PATHS
21
2.1.1
Undrained
2.1.2
Dissipation of
21
Shear
Pore
Pressure
Following
Shear
2.1.3
2.2
THE
Stress
22
Paths
PERFORMANCE
OF
-
25
Summary
VS.
TIME
25
Cohesionless
Sand
25
BRACED EXCAVATIONS
2.2.1
Braced Excavations
2.2.2
Piping, Suffosion
2.2.3
Effects
2.2.4
Braced
of Frost
26
Action
Excavations
Consolidated Clay
in
In
26
Normally
27
6
Page
2.2.5
Braced Excavations
in Overconsolidated
Clay
30
2.2.6
Braced Excavation in Stiff Fissured Clay
32
2.2.7
Braced Excavation in Silt
35
36
2.3 METHODS OF ANALYSIS AND DESIGN
37
Empirical Methods
2.3.1
Semi -
2.3.2
Finite Element Analysis
2.3.3
The
Stress
41
45
Path Method
46
2.4 CONCLUSIONS
CHAP TER
THREE
PROPOSED
IN THE
PRECEDURE
PREDICTION
FOR INCORPORATING
TIME
OF THE PERFORMANCE
OF A
BRACED EXCAVATION
3.0
INTRODUCTION
75
3.1
OUTLINE OF THE PROPOSED METHOD
76
CHAP TER FOUR
CASE STUDY -
PREDICTION OF THE PERFORMANCE
OF A BRACED EXCAVATION
4.0
INTRODUCTION
84
4.1
TYPE OF PREDICTION
85
4.2
PROJECT DESCRIPTION
85
4.3
4.4
4.2.1
General
85
4.2.2
Construction Schedule
86
SUBSURFACE CONDITIONS
86
4.3.1
Soil
86
4.3.2
Groundwater
Conditions
87
NAKAGAWA PREDICTION
4.4.1
Initial Model of Field
87
Situation
87
7
Page
4.4.2
Stress Paths
III
from Initial BRACE
87
Analysis
4.4.3
Laboratory Tests and Revised Soil
89
Profile
4.4.4
A.
Soil Classification
89
B.
Stress Path Tests
90
C.
Coefficient of Consolidation
91
D.
Revised Soil
E.
Contours of Equal Vertical
Revised BRACE
91
Profile
III Analysis
Strain
for Partially
95
Drained Conditions
95
A.
General
B.
Computation of Partially Drained
96
Moduli
Undrained
2.
Consolidation Strains
Dissipation of Excess
3.
96
Shear Strains
1.
Within
95
Due to
Pore Pressure
97
the Excavation
Consolidation Strains
Due to
Dissipation of Excess Pore Pressure
Behind
C.
98
the Excavation
100
of Moduli
4.
Contours
5.
Ko
102
6.
Anisotropy
102
Predicted Loads,
Stab i 1ity
Deformations
and
103
8
Page
1.
General
103
2.
Deformations
103
3.
Loads
106
4.
Stability
107
SUMMARY AND CONCLUSIONS
CHAPTER FIVE
5.0
GENERAL
152
5.1
LIMITATIONS
153
5.2
SUGGESTIONSFORFURTHERRESEARCH
154
5.3
CONCLUSIONS
156
LIST OF SYMBOLS
161
REFERENCES
163
APPENDIX A
GRAINSIZE PLOTS
AND
SQUARE ROOT
CONSOLIDATION PLOTS -
OF TIME
NAKAGAWA SOIL
167
SPECIMENS
APPENDIX B
VERTICAL
NAKAGAWA
EFFECTIVE
STRESS
VERSUS
DEPTH-
182
9
LIST OF TABLES
Table No.
Page
Title
81
3.1
GEOTECHNICAL
3.2
STRESS
4.1
SOIL INDEX PROPERTIES,
4.2
SUMMARY OF COEFFICIENT OF CONSOLIDATION
DATA FROM STRESS PATH TESTS
PATH
PERFORMANCE
82
METHOD
AND CLASSIFICATION
4.3
SUMMARY
4.4
SUMMARY OF DETERMINATION OF PARTIALLY
DRAINED STRESS STRAIN MODULI
4.5
OF SHEAR
STRENGTH DATA
SUMMARY OF STRENGTHS FOR AVERAGE
IN STABILITY ANALYSIS
115
121
124
129
ELEMENTS
151
10
LIST OF FIGURES
1.1
Page
Title
Figure No.
EFFECT OF FORCED DELAY ON A CRITICAL
CONSTRUCTION EVENT
48
BRACED EXCAVATION GEOMETRY
2.1.1
EXAMPLE
2.1.2
STRESS PATHS FOR UNDRAINED UNLOADING
NORMALLY AND OVER CONSOLIDATED SOIL
ELEMENTS
2.1.3a
2.1.3b
2.1.3c
2.1.3d
2.1.4
2.1.5
2.2.1
2.2.2
2.2.3
20
OF
49
STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION FOR
NORMALLY CONSOLIDATED SOIL-NO DEWATERING
50
STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION FOR
NORMALLY CONSOLIDATED SOIL-WITH DEWATERING
51
STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION
FOR
OVER CONSOLIDATED SOIL-NO DEWATERING
52
STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION
FOR OVERCONSOLIDATED SOIL-WITH DEWATERING
53
DETERMINATION OF TOTAL HEAD SUBJECT TO
EXCAVATION AND/OR DEWATERING
54
STRESS PATHS FOR ACTIVE AND PASSIVE
CONDITIONS FOR NORMALLY AND
OVERCONSOLIDATED SOIL
55
STRESS
PATHS FOR EXCAVATION
IN
COHESIONLESS
SAND
56
PIPING/SUFFOSION MECHANISMS
57
INCREASE
STRUT LOAD VS.
IN
TIME
FOR A
BRACED CUT IN STIFF FISSURED CLAY
COEFFICIENT OF
CONSOLIDATION
2.2.4
VARIATION IN
2.2.5
SOIL PROFILE, EXCAVATION, AND
INSTRUMENTATION DETAILS
WALL IN SOFT CLAY, OSLO
2.2.6
SUMMARY OF
SOFT CLAY,
58
FOR A
BRACED
OBSERVATIONS FOR BRACED
OSLO
59
SLURRY
60
CUT
IN
61
11
Page
2.2.7
2.2.8
2.2.9
2.2.10
2.2.11
2.2.12
2.2.13
2.2.14
STRESS DATA FOR PIEZOMETER P-i,
CAES FOUNDATION EXCAVATION
BELOW THE
62
SOUTH COVE SUBWAY EXCAVATION TEST SECTION
PIEZOMETER P-4
63
STRUT LOAD AND PORE WATER PRESSURE VS.
-SOUTH COVE TEST SECTION
64
TIME
MEASURED AND PREDICTED STEADY STATE PORE
PRESSURES-SOUTH COVE TEST SECTION
65
TIME DEPENDENT BEHAVIOR OF TEST CUT IN
STIFF FISSURED CLAY
66
EFFECT OF VARIATION OF TIME TO FAILURE ON
STRENGTH IN UNDRAINED TRIAXIAL TESTS
67
EXCAVATION PENETRATING SILT:
SECTIONS A & B
68
MBTA TEST
MEASURED AND PREDICTED PORE PRESSURE
MBTA TEST SECTIONS A AND B
69
2.3.la
TERZAGHI
& PECK DESIGN ENVELOPES
70
2.3.1b
TERZAGHI & PECK DESIGN ENVELOPES
71
2.3.2
CONSOLIDATION AT THE END OF ONE-DIMENSIONAL
72
EXCAVATION
2.3.3a
CONTOURS OF NEGATIVE EXCESS PORE PRESSURE
FOR TWO-DIMENSIONAL EXCAVATION
73
CONTOURS OF NEGATIVE EXCESS PORE
FOR TWO-DIMENSIONAL EXCAVATION
74
2.3.3b
PRESSURE
CONTOURS OF EQUAL VERTICAL
4.2.1
PLAN VIEW AND PROFILE OF NAKAGAWA SEWAGE
TREATMENT PLANT EXCAVATION - SITE B
110
4.2.2
SITE B CONSTRUCTION SCHEDULE
111
4.4.1
INITIAL PROFILE AND FINITE ELEMENT MESH
112
4.4.2
DETAIL OF FINITE ELEMENT MESH IN ZONE OF
EXCAVATION
113
4.4.3
STRAIN
83
3.1
TYPICAL TOTAL STRESS PATHS INITIAL BRACE III
114
ANALYSIS LINEARLY ELASTIC MODULUS
12
Page
116
4.4.4
PLASTICITY CHART
4.4. 5a
STRESS
4.4. 5b
STRESS PATH
4.4. 5c
STRESS PATH TEST TE-1
119
4.4. 5d
STRESS PATH TEST TE-2
120
4.4.6
REVISED
122
4.4.7
UNDRAINED STRENGTH TRIAXIAL TEST RESULTS
VERSUS SAMPLE DEPTH
4.4. 8a
PATH TEST
117
TC-1
TEST TC-2
118
SOIL PROFILE
123
ESTIMATED CONTOURS OF EQUAL STRAIN 125
COMPRESSION
4.4 .8b
4.4. 8c
ESTIMATED CONTOURS
COMPRESSION
OF EQUAL
ESTIMATED CONTOURS
EXTENSION
OF EQUAL
126
127
SIXTH
4.4.10
SUPERPOSITION OF TOTAL STRESS
CONTOUR PLOT OF EQUAL STRAIN
STAGE
4.4.11
DEPTH OF EXCAVATION
4.4. 12a
TIME FACTOR VS.
-
STRAIN
4.4.9
EXCAVATION
-
STRAIN
SIMPLIFIED
VS.
AVERAGE
PROFILE
PATHS
ON
131
TIME
DEGREE
128
132
OF
CONSOLIDATION
133
4.4. 12b
NORMALIZED
4.4.13
NORMALIZED DEPTH VS. CONSOLIDATION RATIO FOR
TRIANGULAR INITIAL EXCESS PORE PRESSURE
134
4.4. 14a
VOLUMETRIC
PRESSURE
4.4. 14b
4.4.15
4.4.16
4.4.17
DEPDTH VS.
STRAIN VS
DISSIPATION OF
133
PORE
135
VOLUMETRIC STRAIN VS.
OF PORE PRESSURE
CONTOURS OF MODULI
REVISED RUN B
-
CONTOURS OF MODULI
FINAL RUN C
-
DEFORMED FINITE
CONSOLIDATION RATIO
LOGARITHMIC DISSIPATION
1 36
BRACE
III
ANALYSIS
-
137
BRACE
ELEMENT
III
ANALYSIS
-
138
MESH
139
13
Page
140
4.4.18
SELECTED LINES OF LATERAL DISPLACEMENT
4.4.19
SELECTED LINES OF VERTICAL HEAVE
141
4.4.20
CONTOURS OF SHEAR STRESS
142
4.4.21
CONTOURS OF TOTAL SIGMA Z
143
4.4.22
CONTOURS OF TOTAL SIGMA X
144
4.4.23
CONTOURS SHOWING TRENDS OF NEGATIVE EXCESS
PORE PRESSURE
4.4.24
4.4.25
COMPARISON
BEHIND THE
145
OF PECK'S CHART WITH
NAKAGAWA EXCAVATION
ESTIMATED TOTAL STRESS
THE STEEL PILE WALL
SETTLEMENT
DISTRIBUTION
TERZAGHI
4.4.27
SIXTH EXCAVATION
ANALYSIS
STAGE
4.4.28
STRESS
STABILITY ANALYSIS
5.1
LINEAR VS.
NON
5.2
HYPERBOLIC
STRESS
A. 1-A. 6
COMBINED
A.7-A. 14
SQUARE
B.1
PATHS FOR
ANALYSIS
-
148
STABILITY
149
LINEAR STRESS
STRAIN
STRAIN
CURVES
GRAINSIZE ANALYSIS PLOTS
ROOT OF
TIME CONSOLIDATION PLOTS
VERTICAL EFFECTIVE
NAKAGAWA
BEHIND
147
4.4.26
BASAL HEAVE
146
STRESS VS.
150
159
160
168
174
DEPTH,
183
14
CHAPTER ONE
INTRODUCTION
INTRODUCTION
1.0
and
in
dissipation,
to
highly
influenced by
the
Presently
or
excavation
"drained"
pressure
pore
or
constructing "deep"
safety,
adjacent
effect
the
usual
the
and
on
major
potential
response
the
for
can be
facilities
time
of
approach
practice
"unloading"
to
is
use
parameters
of
engineers
and
case
excavations
For
conditions.
deformation
the
excess
time
of
role
of
mass.
soil
common
and
excavation
the
damage
the
and
designing
Design economy,
excavations.
the
of
the role
specifically
the
consider
carefully
should
engineer
An
"undrained"
in
"undrained"
or
the most
clay
and
strength
This
design.
for
assume
idealize
to
is
approach
assumes
following:
(1)
Construction occurs
(2)
No
dissipation
excess
of
during construction
The
(3)
soil
rapidly.
is
strength
pore
pressure
occurs
no
drainage
occurs).
(i.e.,
the
in-situ
shear
undrained
strength.
The
assumptions
"instantaneous"
soils
are
not
above
are applicable
excavation.
"instantaneous"
Actual
and
only
for
excavations
are partially
in
an
cohesive
drained.
15
Although
for some situations
(i.e.
excavation in soil with a very
undrained assumption is
rapid
temporary
low permeability) the
nearly valid at least for design
purposes, many major braced excavations are open
for months
or even years.
Significant pore pressure dissipation
following shear
stressing of
the soil or altered
may
facilitate rapid drainage.
and
significant increases
occur
as well
a consequence unpredicted
in
soil
strength may
in the stress/strain
the soil with time.
Although relatively
few studies of
excavations have been made
the
As
or decreases
as variation
characteristics of
of pervious soil
Undetected layers
conditions may occur.
flow
to observe
performance of braced cuts,
some
instrumented
the effect of time on
significant
To briefly summarize several
observations have been made.
cases:
(1)
Bjerrum & DiBiagio
experimental
4 meter
clay instrumented
influence of
the average
struts
for
deep trench
in stiff-fissured
the purpose of studying the
They observed
force per meter as measured in
increase from 2.3
Measurements
reported on an
time on earth pressure.
tons/meter over
(2)
(1956)
tons/meter
several months
to 7.17
(Sept.
from a braced slurry wall
Boston Blue Clay reported by Jaworski
indicate a gradual and significant
the
to Dec.).
in stiff
(1973)
increase in
16
earth pressure after excavation to the design
depth.
(3)
DiBiagio & Roti
(1972) reported earth and pore
for a braced slurry wall
pressure measurements
Significant decreases and
excavation in soft clay.
in earth and
increases
after
pore pressures during and
completion of excavation
to the
final depth
were observed.
(4)
Lambe
reported piezometer
(1968)
excavation 22
data
for an
feet deep penetrating an
overconsolidated medium Boston Blue Clay.
Negative
excess
pore pressures
in the clay at
the
bottom of the excavation decreased during the 24 day
This
period the cut was open.
decrease
in the strength of the
indicated an overall
soil as well as a
safety with time.
decreasing factor of
The above observations reflect
fact
the
that
time is an
important variable to be recognized by the engineer.
Recently Clough & Osaimi
(1979)
investigated pore
for excavations,
pressure dissipation
including braced
excavations using a finite element model
to determine how
long the undrained case was applicable.
From the results
the
authors concluded
excavation
in clay is
that pore pressure dissipation
likely
to occur
than previously believed and that
should be used with
care.
to a greater
for
degree
the undrained assumption
17
Determining
pressure
occurs
difficult
to
other
The
several
(1)
the
for a
task.
For
phenomena
engineer
rate
design
sands
such
of
The
to
(3)
to
system
can
be
a
be
a
complex
factor
with
transport
(piping).
to
the
assess
and
respect
importance
of
and
is
total
to
be
time
in
for
which
service
(i.e.
the
permanent).
of
altered
imposition
groundwater
of new
groundwater
control.
The
in
changes
cut
pore
design:
excavation
character
the
soil
attempt
support
dissipation of
time may
as
prior
temporary or
(2)
to which
given braced
should
variables
The
degree
total
boundary
stress
conditions
conditions
distribution
due
and
due
to
excavation.
(4)
The
on
(5)
effect
the
The
for
such
Critical
such
a
and
after
delays.
final
phase
and
and
strikes
excavation
delay-(i.e.
hence
may
stage
for
and
parameters.
labor
etc).
estimated
conditions unforseen
extend
performance.
as
placing
can be
(1977)
(just
prior
slab)
at
a major
strikes
accurately
unexpectably
such
& Davidson
caps
be
influence
events
dissipation
deformation
contractor
of construction
pile
pressure
time may
an excavation
Clough
and
forced
excavation
backfilling
foundation
of
labor
time
pore
strength
weather
as
construction
bracing
excess
construction
reasonable
events
soil
effect
Although
of
most
report
to
the
office
support
or
influenced
one
case
casting
bottom of
a
building, was
by
where
18
adversely affected by an unexpected delay.
be used
to support raker bracing for
the sheet pile wall.
carpenter strike delayed pile cap formwork
during which the excavation stayed
The slab was to
open and
for six days
the walls
inward.
After 20 centimeters
remedial
support was applied by
pile cap
excavation to retard further movement.
over
30 centimeters
crack
versus
time and
Corbet,
excavation
workers
strike
of concern
benefit
and Langford
Although the
for
authors
apparent
this excavation.
reported on a braced
a national building
specific results of
state that
to the author
the
this delay are
the delay was a cause
that
the profession would
time.
The behavior of
penetrating intermediate soils
types
such as
are of particular
engineer
1.1 shows movement
for
(1974)
large
from additional research and measurements of
excavations
etc.
Figure
A
the stability of the excavation.
excavation performance vs.
and sand
occurred.
Eventually
led to delay of a critical period in
not reported, the
is
the wall.
in stiff London Clay where
excavation.
It
temporary filling of the
the pertinent events
Davies
crept
of movement had occurred some
of wall movement
appeared behind
A
silts,
clayey silts
interest.
between the clay
and clayey sands
The demand for
the
to design with economy and safety warrant
understanding of the role of
soil subject
a better
time and drainage on behavior of
to excavation unloading.
19
1.1
THESIS OBJECTIVE
The
apply
objective of
time
several
simple
over
time
discussed.
will
to
predict
be
the
to
formulate
effects
deformations
discussion of
cases,
for
the
Several
discussed.
of
of
A
and
pore pressure
an excavation.
method will
in the
lab
braced
and
to predict
for a
excavations
design and
type
include
stress
the
excavation.
A
path
role
of
of
time
for
of measurements
will be
analysis
Stress Path Method
study.
element analysis,
effect
significance
current
applied
This
the
several braced
outlined and
deep
the
is
THESIS SCOPE
Following
made
thesis
a method which includes
change with
1.2
this
approaches
approach will
prediction
of
a
a composite
of
finite
testing
time
of
in the
soil
be
case
specimens
study
of
a
Strike
30-
Elevation Om
25:
5
1_3
.
3
2
0.
w 202
Li
0
DAY 6
Poured Pile Caps0
Pile Caps Partially Filled With Soil
-J
10
Elevation Om
o East Sheetpile Wall
3 West Sheetpile Wall
5.
5Excavation of Pile Caps(-Ilm)
DAY.3
0-
Excavation to Subgrade (-9.5m)
0'
' ' ' 5 ' ' ' ' 'O ' ' ' '2 '
' ' ' '
ELAPSED TIME SINCE START OF EXCAVATION (DAYS)
EFFECT OF
FORCED DELAY
115
DAY 7-14
FrOM CLOt&-CL"
ON -A CRITICAL CONSTRUCTION E VENT
j CA'IDSON (9-17)
FIG. 1.1
21
CHAPTER TWO
THE ROLE OF TIME
INTRODUCTION
2.0
this chapter the effect
In
outline
the importance of excess pore pressure dissipation
Related observations and
excavations.
for braced
of pressure and time
measurements
be
simple examples will be discussed to
several
deformation for
of time on strength and
discussed.
from the
Various current methods of analysis and
design will be reviewed on the basis
incorporate time
for
of how the methods
Limitations and assumptions made
effects.
each method are discussed.
2.1
STRESS PATHS
Use of stress
1967,
paths and
Lambe & Marr 1979)
within which
for
literature will
the Stress
Path Method
(Lambe
provides an organized framework
Stress paths
the field problem can be studied.
field situations can be modeled using standard
tests,
laboratory
such as the
three dimensional triaxial
test.
2.1.1
Undrained Shear
At this
and 2.1.2
point
convenient to refer
constructed by the writer.
are an example of
effective stress
clay soil
it is
to Figures
Shown in
the
braced excavation geometry and
paths
2.1.1
figures
total and
for normally and overconsolidated
elements adjacent
to
the excavation.
22
The
total
between 2A and
2B represent the
experienced by soil elements
stress
the wall
stress
type
of unloading typically
1 and 2.
change for element 2 at
excavation is
1A and 1B and
stress paths between points
The mode of total
the center
extension unloading.
line
of the
Soil element
1 behind
experiences compression unloading or an "active"
condition.
Typical effective
can be
stress
paths for
1A and 1C and points 2A and 2C
traced between points
on each
p-q plot.
The horizontal
at any given value
of q is
the undrained shear
width
of
the shaded
area
the value of excess pore pressure
generated by shear.
The
which
shaded region also represents
the effective stress
conditions.
effective
a material
drained
2.1.2
There
for partially drained
in
silt
this region.
Rapid
excavation in
for example, may exhibit partially
behavior.
Dissipation Of Pore
Strength and
Pressure Following
stress-strain modulus of the
dependent on the
pore
lie
are an infinite number of possible
stress paths
such as
paths
the region within
effective stress
path.
are
soil parameters
Figure
important
in the
soil
are
Since changes
pressure directly affect the effective
these changes
Shear
in
stress path,
field and when estimating
for design.
2.1.3a-d shows
geometry of Figure 2.1.1
stress
for
paths
for
the example
typical overconsolidated and
23
The plots
normally consolidated clays.
exhibit
in the figure
type of pore
a range of situations bracketing the
to occur during and after
pressure behavior likely
to the design depth.
excavation
made in order
shear due to
plots; undrained
to draw these
occurs
excavation
A simplifying assumption is
first and then is
followed by
dissipation
of excess pore pressure.
pore pressure results
Excess
release
due
to excavation and/or from decrease in pore
pressure due
to altered flow conditions
(i.e.
dewatering).
With respect to dissipation
pressures
following qualitative
after
the
construction of
2.1.3a--This
strength
of excess
Clay
soil will
(i.e.
move
towards
the failure envelope)
pore pressure
positive excess
result in
occurs at
element
the
to dissipation of
pore pressure caused by dewatering
settlement.
The
soil will experience
an increase in strength with consolidation.
vertical
to
Consolidation heave will occur.
2.1.3b-- Consolidation due
will
This
the bottom of the excavation and behind
excavation wall.
in
undergo a minor decrease
the original pore water pressure.
(2)
pore
conclusions can be made
following dissipation of excess
both
construction
the Figure 2.1.3 plots:
Normally Consolidated
(1)
total stress
from the
strain will
Net
be higher with dewatering
for
1 due to additional compressive strains at
24
constant
shear stress.
strain for element
However the net vertical
2 will be
less
associated with no dewatering.
steady
state
If two
strain
dimensional
flow conditions are attained
steady-state pore pressure
the
can be determined
from
a flow net.
Although
steady state
flow conditions will be reached, this
condition represents
(3)
than the
2.1.3c--For
to
an outside
bound.
an increasing over consolidation ratio
the effective stress
due
it may be unlikely that full
path will
shift
to the
right
the generation of large negative excess
pore pressures.
result
Subsequent consolidation will
in a substantial decrease
in strength
and a consolidation heave.
(4)
2.1.3d--If
the absolute value of change
pressure due to
to or
altered
in pore
flow conditions
is
greater than the absolute value of
pore pressure due
increase.
to shear,
Otherwise
the
equal
the excess
the strength will
strength will
decrease
with time.
For a given excavation with excess pore
generated by shear
pressures
and dewatering the net excess
pore
pressure can be estimated by
super-imposing or adding
two.
this.
Lambe
(1968)
discusses
schematically illustrates the
field situation.
the
Figure 2.1.4
procedure for
simplifying the
2.1.3
Stress
The use
25
Paths---Summary
of stress
paths
to
illustrate
the various
possibilities assists the engineer in his
judgement.
Qualitatively the pore pressure-strength-strain relation
clarified
stress
in one's mind.
paths
pressures
to
(1970)
illustrate active and passive
for excavation
overconsolidated clays.
plots
Similarily Henkel
earth
For
comparison, several
paths.
recognizes the utility in
type
applying this
of Henkel's
a slightly
different graphical portrayal of stress
Henkel
of approach
may behave.
THE PERFORMANCE OF BRACED EXCAVATIONS VS.
Cohesive
soils
TIME
are assigned low permeabilities
compared
to cohesionless soils which have high permeabilities.
general
for
projects
changes
as
the engineer in his understanding of how a given
excavation
2.2
uses
in normally and highly
are reproduced in Figure 2.1.5 showing
an aid to
is
the time associated
involving
in
with most construction
loading or unloading of the
flow conditions,
in cohesive soils.
some degree
For sands
In
soil or
of drainage occurs
the condition of
full drainage
is achieved rapidly.
2.2.1
Braced Excavations
For excavations
In Cohesionless
in sand deposits steady-state seepage
conditions are achieved rapidly.
paths
illustrating
Sand
Figure 2.2.1 shows stress
this behavior.
Since
sand has
a
relatively high permeability pore pressure dissipation is
virtually instantaneous.
The total
stress
path equals
the
26
stress path and the
effective
Therefore time does not play a
be obtained from a flow net.
Although the following two sections are
significant role.
not
to
2.2.2
particles via high
seepage gradients into
Figure 2.2.2 graphically
for
excavation.
Peck
(1969)
resulting from migration of sand into the
ineffective.
and render them
anticipated by field montoring of
of the excavation
Also at
presence of suspended
The mechanics of this
(1942)
and D'Appolonia
Effects of
(pump
the bottom of the excavation piping
were elucidated by Terzaghi
2.2.3
flow into and out
for the
failure by heave may occur.
(1967)
through cracks or
conditions can be
Serious
a sheet pile wall.
& Peck
cut.
time migration of silt size particles can
Particles can also be piped
soil particles.
points
control may lead to damaging
clog construction dewatering wells
effluent)
the
the mechanisms
illustrates
suffosion and/or piping.
Over a period of
holes in
time
piping or suffosion.
to as
inadequate groundwater
settlements
are present,
to migration or erosion of soil
is referred
This migration
responsible
time plays in the
cohesive soil).
(vs.
gravels,
silts and sands or
a role with respect
out that
soil
they serve
Suffosion
Piping,
Where
plays
the different type of role
in cohesionless
excavation
objective,
thesis
the
specifically bound to
illustrate
steady state pore pressure can
phenomena
and discussed by Terzaghi
(1971).
Frost Action
Field observations have
shown the
effect of frost action
27
to be
substantial.
struts may increase
Several
cases show the
several
fold.
monitored performance
1
Pappas & Sevsmith
of a deep braced cofferdam in
sensitive Leda clay. Abnormally
load were detected
loads in the
large increases
in strut
during December excavation.
heating of the adjacent soil
resulted in rapid
reduction, the problem was concluded
Since
load
to be one of frost
act ion.
DiBiagio & Bjerrum
within
in
and at
load in
lower
observed after
the surface of an excavation
the upermost struts, and severe
bracing
struts.
(1956)
levels buckling some
trench, decreases
increases in the
of the walers and
Although reliable deformation measurements were not
available, visual
observations
led to
the conclusion
upward expansion of the soil during freezing
unusual
shows
ground freezing
changes
the
caused the
in distribution of pressure.
dramatic
time vs.
Terzaghi & Peck (1967)
that an
Figure 2.2.3
strut load behavior.
report
that braced cuts
in Oslo &
Chicago were subjected to below freezing weather. They
observed earth
greater
pressures climb to magnitudes several
than those prior
Ground
freezing as
to
freezing.
these cases
unpredictable and radical behavior.
frost
lenses
is
times
time dependent,
the
illustrate
Since
the
can result in
formation of
potential for
damage can
be anticipated by monitoring the wall movements and
strut
loads.
IRefer
------------------------------------------------------------to
Clough and Davidson (1977)
2.2.4
28
In Normally Consolidated Clay
Braced Excavations
For clays
one expects a soft normally consolidated clay
to have a lower coefficient
of consolidation than an
overconsolidated clay since
this value
be higher
shown
in recompression than
in Figure 2.2.4
rate.
At
least
generally
found to
in primary consolidation as
for a varved clay.
expect soft clay to dissipate excess
slower
is
We would
therefore
pore pressures
at a
one braced excavation case illustrates
that
normally consolidated clay the
ideal undrained condition is
not sustained over the course of time
excavation.
DiBiagio and Roti
for
a temporary
(1972) measured
the
magnitude of total earth
pressure,
deformations of a braced
slurry-trench wall
in Oslo.
Below the clay
the wall was
bedrock.
Measurements were made before,during and after
excavation.
Figure
2.2.5
geometry of the excavation
layout.
pore pressure and
shows the
as well
a soft
the
profile and
instrumentation
pressure
two piezometers.
The measurements during the excavation stages
Figure
2.2.6 indicate only minor decreases in
occured until
groundwater
shown in
pore pressure
the excavation approached bedrock and
control was facilitated
Consequently, the pore pressure at
was
through
this
layer.
the bottom of the clay
significantly reduced, accompanied by a marked
in total
clay
keyed into a pervious
soil
as
in
Instrumentation included fifteen earth
cells and
for
earth
pressure on the wall.
remained open to
reduction
The excavation
this depth for approximately 200 days.
A
29
downward gradient
in the
settlements during
this period before
excavation bottom with
pore
earth
the course of
total
its
increasing
in pore pressures.
For the
fact
location of the
that the
upward towards
the center
concludes that
this
specific zone
correct as
decrease
Coupled with the
force moved
layer with time,
central point of
the
this
soft clay
As a practical matter,
the undrained assumption may
looking at the
careful study,
center of the clay
resultant earth
of the
behaved partially drained.
not
total
a small decrease in pore
the time of construction.
is
the
initial value.
pressure over
However,
The
the construction of this excavation
piezometer PZ-9 shows
writer
slab.
earth pressure varied dramatically due primarily
to changes
layer,
towards
of the
from this point on
the rate of settlement and
pressure back
Over
the "sealing"
the construction of a base
pressure built up steadily
decreasing
the
clay contributed to consolidation
clay mass
as
this
be reasonable.
a whole
piezometer PZ-8 clearly
in
the assumption
shows.
the writer concludes that because
After
the
in pore pressure in PZ-9 occurred before dewatering
and remained relatively constant, dewatering did not
significantly affect the
center of
the clay and the negative
increment of pore pressure was due solely to changes
total
stress.
layer shows
changes
in
Conversely
the
lower portion of the
the effect of both changes
flow conditions.
in
total
in
clay
stress
and
30
is
Although admittedly this
that
illustrates
pore pressure dissipation can be a factor
even for impervious walls
Dissipation of
soft clay.
in
positive excess pore pressures resulting
large pressure decreases against
lead to
construction.
from dewatering can
the wall during
More rapid dissipation of excess
can be expected
pressures
it
only one case,
pore
for sheet pile and other
non-slurry-trench walls which are characteristically more
permeable.
2.2.5
Braced Excavation In Overconsolidated Clay
interesting conclusions
Some
undrained
from field data suggest the
assumption to be seriously
in error
for
the
overconsolidated clay.
Referring now to Figure
piezometer readings
2.2.7, Lambe
Very litle
the
after excavation.
a value
Thereafter
of negative excess
path towards
follows
The
P-1 are reproduced
the pore pressure increased
less than u.
porewater pressure).
pore pressure moves
failure and results
as Lambe concludes
24 days.
in
the pore pressure immediately
greater than u. but still
pre-excavation static
It
is
for
in this excavation.
for a point at piezometer
Note that u. ,
figure.
the CAES building
The excavation was open
dewatering was attempted
stress paths
observed
from the medium clay layer at the bottom
of a temporary braced excavation for
foundation at MIT.
(1968)
(the
The dissipation
the effective
stress
in a consolidation heave.
that
there
is
to
a progressive
decrease in strength leading to a decreasing factor
of
31
time.
safety with
is
Therefore the end of the unloading period
the most critical
the unloading period
replaced in
is defined
just before
as
Hence,
the excavation.
The end of
this excavation.
time for
load is
the
the most critical
condition occurs some time after completion of the
excavation.
Observations
slurry-trench and sheet
Figure
pore
deformations
and strut
2.2.9 shows a redrawn
pressure versus
slurry wall.
in stiff clay
pile walls
subway excavation in Boston (see
pressures,
for braced
and measurements were made
Observations
loads were measured.
compilation of strut load and
section at
of piezometers
behind
the wall
feet decreasing to 82
the wall after
in
the
feet measured
loads
strut
pressure measured
figure.
total
(less
increased
Following mud
steadily as did
in the piezometer
than 1 inch)
resulting from construction.
joints was observed.
measured pore pressure vs.
predictions
106
in piezometer P-4 behind
P-4 as
the change
water pressure can be associated with altered
wall panel
of
shown
Since measurements showed very little
outward wall movement
conditions
in water
head
the final cut had been made.
slab placement, axial
pore water
from an initial
the
indicate
excavation was accompanied by steady decreases
pressure
Pore
Figure 2.2.8).
for a test cross
time
for a
in pore
flow
Seepage
through
Figure 2.2.10 shows
depth.
Steady state seepage
compared well with end of construction pore
pressure measurements.
Hence,
it can be argued that
the
32
drained
parameters,C and
are more
applicable for
this "end
of construction" case.
In constrast to
Oslo,
the slurry wall
pore pressures
significantly.
throughout
case in
the soft
the stiff clay drop
Imposition of new boundary water pressure
conditions are met with a relatively quick drainage.
the
strut
reflect
over
loads at
the strut
the
life
structure.
in strut
DiBiagio
(1956)
loads
for
trench
studied.
gradual
during
excavation in
Figure 2.2.11
load
shows a section of
profile and
(Sept.
test data.
to mid Nov.)
show a
winter load
(see
to the
also Figure 2.2.3).
total
intense period of rainfall
is
followed by
pressure observed for Autumn
Pore
pressures
pore
pressure versus
plotted in Figure 2.2.11
time over this
clay facilitate access
Autumn
earth pressure show
increases following periods of rainfall.
value of pore
the
type of soil
frost action and previously
section 2.2.3
rainfall data compared
most
this
and marked increase followed by enormous
discussed in
figure
in stiff marine clay Bjerrum &
the Autumn
increases attributed to
sharp
in the
Stiff Fissured Clay
the excavation, corresponding soil
Strut
trend
are seen in adjacent struts.
interesting case
the experimental
The
load by a factor of approximately
Braced Excavation In
One
is
loads which the bracing will experience
Similar trends
2.2.6
Also
the end of excavation do not accurately
of the
shows an increase
1.5.
clay in
the maximum
in mid November.
show the measured
period.
of water to
The
The fissures in
the clay mass.
Total
33
release from excavation in fissured and weathered
stress
clays
lead to
can
further opening of the
permeability.
increases in
conditions leads
such
Prolonged construction under
progressive weakening or softening,
increases in the
as
as well
to
fissures and
in pore pressure.
rapid changes
dramatically
The effect of fissuring on stability is
illustrated by the short
term slip failure of an unsupported
excavation
in London Clay reported by Skempton and
LaRochelle
(1965).
The results
The
strengths measured
of the average
tests.
from triaxial
triaxial tests and the actual
pressure migration within the
It was
fissuring.
the
for
Conventional
tests
to
in
failure to
intact clay,
tests,
and
run at a
pore
(2)
time
to
strength decreased.
failure of 15 minutes
time to
the strain rate due
of strain rate on strength
strength versus
tests
(1)
strain rates much higher than and
pressure migration.
triaxial
The authors
shown that by increasing the
triaxial
unrepresentative of
influence
undrained
the difference between the measured strengths
attributed
correspond
the
estimated mobilized shear strength in
approximately 55%
clay mass was
failure
fissured clay as
in stiff
slip occurred shortly after excavation had been
The
completed.
the
lend
of this study
understanding to braced excavation
well.
to
soil
succeptibility of the
Figure
time to
2.2.12
failure
performed to
to excavation.
is attributed
shows
to pore
the results
for a series
This
of
of undrained
study this behavior.
Secondly,
34
the
authors
the
fissuring can weaken the clay during excavation.
Several
conclude that at
of the
least
five
important factors are,
along fissures
leading to
increases
factors related
to
absorption of water
in water
(softening), reduction of strength to
zero as
content
fissures open,
and progressive failure.
Quantifying the effect of
fissures and the rate of
softening on stability and deformation to predict
is difficult.
performance
Corbet et al
(1974),
observations made
for
and Cole and Burland both reported
a raker braced diaphragm wall
meter deep excavation for a basement
London Clay.
In view of
in
in a 20
stiff fissured
the uncertainties cited
in the
previous paragraph, detailed construction performance
monitoring was undertaken.
were monitored.
Several
of
Wall movement
and verticality
Earth pressure however, was not monitored.
the conclusions
drawn by the authors
after
observing the construction performance are reiterated below.
(1)
Wall movements showed a clear
(2)
Early
internal
time dependence.
support placement is
essential
to minimize movements.
(3)
Performance monitoring
control
is
important for
and is of research value
for
construction
future
exca-
vat ions.
(4)
Inward wall movement
progressive
of the
clay.
is
associated with a
softening and reduction in
The
greatest
stiffness
reduction in stiff-
35
ness was
found to be near
the wall.
This
is
attributed
fissures due to lateral
In summary, one
significant factor
excavation
to the opening of
stress
can clearly see
release.
that
time
fissured clay.
and measurements
Although
conclusions of practical value at
undrained assumption is not applicable
stiff
fissured clay which remain open
and minimizing construction time
Lambe
two
ic
et al,
2.2.13.
and MIT
(1972)
monitored
underlain by glacial till
The test
for
sections,
with
silts
No
time was measured.
the studies
was that
the pore
pected to
is desireable.
literature.
reported on a study of
in fill overlying
as
Section A and Section B were
significant strut
against
load variation
However, one conclusion reached
for braced excavation
pressure behind
be less
organ-
seen in Figure
stresses and deformation and compared
predicted behavior.
in
information on excavation
instrumented Boston subway cuts
silt,
The
important and is
in silt has been reported in the
(1969),
time.
in Silt
Very little well documented
performance
can make
for several months,
recommended,
Excavation
are needed
to excavations
performance monitoring is
Braced
additional
this
construction
2.2.7
a very
of field situations
to advance our understanding of this case we
several
is
for load and deformation behavior of
in stiff
observations
the ground surface behind
in
sands and
the excavation can be ex-
than static due to construction.
agreement between the final measured pore pressures
Some
and
in
36
steady
state pore
pressures predicted by
analysis
(FEDAR, Taylor and Brown
pressure
in
indicates
the pore
two test sections
the upper fill and
stiff
Therefore general conclusions by
soil
representative of the
lower strata.
the writer regarding
However the cases
be made.
in silt cannot
penetrate several
penetrate silt,
truly representative of an excavation in
conditions are not
to
2.2.14.
See Figure
these
Although
excavation
element
the silt was probably in a transient state near
steady state.
silt due
1967)
finite
do
fact that many excavations
soil types and cannot be
are
easily
categorized.
studies are valuable case histories.
These
illustrate
the
They
type of construction monitoring data which
predictions of construction performance can be evaluated from.
As
a result,
our understanding of braced excavations
The reader
extended.
additional details.
like
BRACE
is referred
Use of
finite
to the references
can be
for
computer programs
element
and FEDAR to model braced excavation and
flow
respectively showed encouraging predictive capabilities.
2.3
METHODS OF ANALYSIS AND DESIGN
The
following currently used methods
design will be discussed as
of time
of analysis and
they relate to
effects.
(1)
Semi-empirical Methods
(2)
Numerical Analysis Methods
(3)
The Stress Path
Method
the
incorporation
37
Semi-empirical Methods
2.3.1
Several well known semi-empirical design methods are
Terzaghi and Peck Method
(2)
Tschebotarioff Method (1973)
(3)
DM-7
are similar and are
strut
loads.
Peck presented the original apparent
envelopes
published version.
derived
from classical earth
method
is
of strut
referred
reliably measuring
the apparent
loads
to as
(1974) is
pressure
theory and actual
Hence
in excavations.
semiempirical.
stresses against
stress distribution
the
Difficulty in
sheeting required
The envelopes
intended to
give maximum values of strut
experienced
and are not
load to be
truly representative of the
adjustments have been made to accomodate newer
envelopes
of the
2.3.la and
for
sand
is
based
for braced excavations
actual
and
observations
2.3.1b show the
Terzaghi and Peck Method for
The pressure envelope
load measurements
are
Over the years modifications
and experience. Figures
the
to be inferred or
backfigured from the strut loads.
stress distribution.
the most
The design envelopes were
recent
measurements
in sand or
for braced excavations
in 1948
Peck, Hansen & Thornburn
in clay.
will
this design approach.
discussed to illustrate
pressure
(1967)
Only the Terzaghi and Peck Method
Terzaghi and
in
commonly used
to estimate maximum lateral
They are intended
practice.
1967)
(Navdocks) Method (1971)
These methods
be
(1948,
(1)
the:
design
sand and clay.
in part on strut
in New York,
38
An equivalent uniform earth
Munich, and Berlin.
was
fit through the apparent pressures
in
pressure
the excavation.
Several qualifications attend the application of this method
for sand.
The authors emphasize
(1)
that
the diagram has been
developed from a limited number of excavations
varying in depth
The diagram is
(2)
from 28'
to 40'.
distribution for
a pressure
estimating the maximum values of strut
expected
bottom of
the cut.
opinion),
seepage or
assumed
to be below the
(in
Consequently,
points
for
out
is
(water level
Application of the Terzaghi and Peck
sands must accompany an awareness of
can be
should
the writer's opinion
be added especially since
substantial.
the
incorporated into
such
the groundwater
pressures which may be experienced over the
structure
below cut)
the bottom of
problem cannot simply be
conditions. Also, in
soil behind
time related effects have been
piping and piping heave at
This
(1973)
seriously in error.
to be
any pressure envelope.
for
assumption
detrimental
associated with
excavation.
this
Ries
impervious diaphram type walls
typically retard drainage of the
likely
For sands
that
the writer's
pressures should
static water
pressure distribution.
the wall,
method
is
be added to the
which
to be
for similar cuts.
groundwater level
The
(3)
loads
life
of the
these pressures
39
Several relevant
the
facts one should be aware of when using
of the Terzaghi and Peck method are
clay envelopes
summarized below.
(1)
Cuts
are
or undrained condition is assumed
Average undrained strength
side
(2)
The)=0 condition
assumed to be temporary.
is
the cut
Chicago)
from which
(Oslo and
test cuts
from the
the data
the envelopes evolved
included
in strut load
increases
measurements showing large
these
during cold weather,
for formulation of
measurements were not used
the
freezing
Therefore the effects of
envelopes.
the
the clay along
of
used.
Although
due to freezing
to prevail.
should be considered separately.
(3)
The authors
(1967)
available data on cuts in
clays,
and clayey sands
yet to be worked out.
(1969)
reports that
the
However more recently, Peck
trapezoidal
five cuts
in stiff clay
could be used
that limited
drained behavior and
appropriate drained strength
input
clay envelope
into an
equation for earth pressure
stiff
the
parameters
equation for Ka.
as a
data for at
deep cut in dense clayey sand and
sandy clay shows
sandy
design envelopes have
etc.,
conservatively and therefore
least one
clays,
stiff intact
fit the measured values of
guideline. Peck suggests
little
due to
admit that
can be
Presumably, the
for excavation in sand
40
is then modified
(4)
Use of
to
discussed by
Peck 1969)
in
dependent behavior.
for stiff
the authors
(Terzaghi and Peck
(1957)
This
which
suggested that
maximum design pressure,
showed
time
case has been discussed
the writer in earlier sections
The authors
fissured
light of the measurements made
by DiBiagio and Bjerrum
by
expression.
the trapezoidal envelope
clay is
1967,
include this
the
of this
paper.
lower value
.2WH be used
for
if movements
of the sheeting are minimal and construction time
is
short.
If these conditions
of the higher pressure value
.4VH is recommended.
in an indirect way have
assigned some
to time
In summary,
methods provide
loads.
although
of
Hence Terzaghi and Peck,
fissured
strut
do not apply, use
it
importance
for
stiff
clay.
is
the writer's
a useful
opinion that
these
guideline for estimating maximum
The method has been
to extend
effects
tempered with experience
the scope of the
Terzaghi and Peck method
more experience
for a large variety of cuts
The
of the method should be realized and may be
limitations
understood
by studying the evolution of its
Major braced cuts
designed on
open for extended periods
the basis of
this method alone.
is
required.
formulation.
should not be
The engineer's
understanding of the excavation problem may benefit by using
other more
fundamental
techniques.
41
2.3.2
Finite Element Analysis
Over recent years the
advent of the high speed digital
computer has enabled numerical analysis
and viable
technique for
problems .
The
sets
of
use
equations
of
sets
of
equations
solving complex engineering
the
electronic
by matrix
mathemat icaly model
be
c omputer
algebra
problems
could
in
set
al lows
detail *
up
Appl ication and theory
documented
Zienkiew icz 1967,
analys is .
in
the
the
programs
the
the engineer to
such
solution was
too
Element Method is
(Desai and Abel
literature
over
solve 1arge
hand.
Fini te
Bathe and Wilson
Subsequently,
elem ent computer
of
to
Previously
the
but
complica ted to achieve practically by
now well
to become a popular
197 6)
1972,
for engineering
decade several
last
finite
to model construction of braced
e xca vations have been developed
and used by several
inve stigators including Wong (1971),
Jaworski
(1973)
and
Clou gh and Duncan (1971).
Advantages of using this
(1)
Complex
soil and
technique include:
structure geometries and
properties can be modeled.
(2)
Construction sequence and details
(3)
Detailed information on stress
can be
changes
simulat ed.
and
deformations can be obtained.
(4)
Parameter studies can reveal
of
(5)
the relative
input data (strengths, moduli,
and penetration
etc.)
Critical stages
of excavation
import ance
sheeting stiff ness
for a given excavation.
can be predicted.
42
limitation lies
Nevertheless, even
soil
in modeling the
in the difficulty
sheeting interface).
soil
interaction (i.e.,
structure
One such
to be overcome.
limitations have yet
Some
stage of
in the relatively young
development
for finite element modeling of excavation,
encouraging
results and
in
practice,
and Kenney
(1970),
and others have demonstrated the powerful
the method.
applicability of
The
finite element program developed at MIT for analysis
called
of excavation is
and Jaworski
(1971)
The
program in its
present form will model
behavior of the
The program does
modulus.
strength, modulus,
pressure
which
include the
the effects
strain
elastic
of time on
If necessary,
dissipation).
effect of time
Conventional
such a program is the undrained
undrained
modulus
analysis) or
case
not model
or deformations.
loads
stress
effects must be indirectly considered by inputing
parameters
for
the
or bi-linearly
a linear
soil via
for details.
(1973)
theses by Wong
to
is referred
reader
The
BRACE.
the
these
Duncan and Chang
(1974),
Clough and Tsui
Palmer
(1972),
Cole and Burland
MIT (1972),
(1972),
Indeed,
insights have been gained.
to model
soil parameter
the undrained
drained parameters,
C
pore
(e.g.,
soil strength
and
case
input
and
(total
for
stress
the drained
(effective stress analysis).
Pore Pressure Dissipation
Recently, new insight
into
the evaluation of the
validity of the undrained assumption and total
soil
stress
43
for excavation has been presented by Clough and
analysis
to model
technique
TIME-CONSTRUCT and at
authors
(Clough 1980)
interest
are of
discussed
this
the study was
for
not available
documentation
its
since
is
computer program
this writing is
In any event,
complete.
purpose of
The
The name of
excavation.
distribution
given rates of
pressure dissipation occurs during and
to show how pore
after
for
excavation sequence
(meters per day).
excavation
finite element
the
The authors used
(1979).
Osaimi
is not
the published results by the
to the engineer and will
be
following paragraphs.
in the
Using TIME-CONSTRUCT Clough and Osaimi analyzed several
cases.
excavation are shown in Figure
the one
central protion of
that
decreasing
drainage represent
the bottom of the
the excavation
For wide excavation
2.3.2.
unloading and
dimensional
dimensional
of a one
Results of the analysis
cut.
The
figure
to
corresponds
rate
the
shows
an
increase in
the percentage of consolidation at the end of
construction
for
the wide range of permeabilities analysed.
Figures 2.3.3a
two
and b summarize
the
analysis
dimensional excavation for cases of both
nonlinear
pressure
soil behavior.
excess pore
the pore pressure
response at
the bottom of the excavation
contours
is
essentially one
Dissipation of the excess
occur vertically.
Of
of negative
linear and
Contours of negative
shown indicate that
dimensional.
results for
general interest,
excess pore
pore pressures will
in
pressure
Figure 2.3.3a
for no wall
in
44
are shown
place
in the
magnitudes
can conclude that
Therefore we
of negative excess
somewhere between
the two
consolidation would occur for
impermeable
Note that
this
pressure would be at
In any event more
cases.
the sheet pile wall
of drainage
due
to dewatering which
excavation construction.
a result,
As
pressures due to
produce an upward movement of
consistently show settlement
time,
of the
(1)
we can conclude
the
shear alone will
the soil mass behind
the
for many case
Since measurements and observations
studies
than for
analysis by Clough and Osaimi does not
dissipation of excess pore
wall.
the
type.
the role
accompanies
with
pore
the
for
(sheetpile),
of a more pervious wall
realistic case
consider
inhibits
of an impervious wall markedly
consolidation.
the
As would be expected the
linearly behaving soil.
presence
values
for comparison with the supported excavation
occurs behind the wall
for such excavations
one or more
following:
The dissipation of negative excess
due
to shear behind the wall
or larger positive
pore pressure
is negated by equal
excess pore
pressures resulting
from dewatering.
(2)
The heave movements are non-existent behind the
wall due to greater settlement
inward wall movement
the bottom of
resulting
and/or loss
from
of ground towards
the excavation with time.
45
including surcharging by traffic or
Other factors
(3)
equipment as Clough & Osaimi
One important conclusion was
their study.
as a result of
occurs
fact
is
probably based on
the commonly
generally
field
than predicted by
Extrapolating test results
in the lab
undetected drainage
thick
likely to occur more rapidly.
several times more rapidly
specimens
"end of
further note that
They
that consolidation in the
available methods.
the
field is
latter conclusion
accepted
The undrained,
low permeability clay.
consolidation in the
This
drawn by Clough and Osaimi
unlikely to occur even in
construction" case is
deposits of
suggest.
in analyses
of
the
field
layers may exist may
using small
situation
where
explain some of
discrepancy.
2.3.3
Stress Path Method
The
Lambe's
Path Method is
Stress
understanding and analyzing a given geotechnical
Lambe
problem.
(1967)
and Lambe
for both
a useful method
and Marr
(1979)
engineering
describe
the fundamentals and applications of this method.
By
selecting
and analyzing representative or
"average" soil
elements,
one can attempt to estimate the
stresses and
strains
that will
occur
in the
phase of
field for each
construction.
For a supported excavation one can subject
representative
stresses,
soil specimens
apply the
to the
total stress
excavation and measure
in-situ
changes
the strains,
initial
associated with
pore pressures
(and
46
and coefficients of
hence, effective stresses),
consolidation and
lateral earth pressure, K..
Of course the method has
Sample disturbance
aware of.
affects measured values of
coefficient of consolidation, strength,
determined
tests
path
the initial
in
engineer.
the evaluation of
performance of
present
to run.
to varying
Many
degrees
geotechnical
if the engineer is
the
the
of the
aware
predicted versus measured
geotechnical
actual
Stress
and the applicability of this method
The value
limitations.
2.4
not
of the method outweigh
The advantages
limitations, particularly
lie in
is
K. in the field.
available to the
other methods
the
K,
can be both expensive and difficult
limitations however, are
of these
and modulus.
initial stresses
from reloading to the
truly representative of
should be
one
limitations
some
projects.
CONCLUSIONS
The measurements from the case histories
literature show that time
dissipation)
are of
excavation.
For cohesive
exist
effects
significant
(pore pressure
importance
Recent numerical
include
in error and may be
excavations.
techniques allow analysis which may
the effects of
time, but most use
stress-strain parameters.
have non-linear
conditions
the undrained assumption is
only a design simplification which is
seriously in error in some
in braced
soils partially drained
during construction and
from the
cited
Other numerical
parameter models,
linear
techniques which
are expensive and
47
difficult
Clough
to use
and
and
Osaimi
don't
have
consider
developed
a
time
effects.
computer
program
(TIME-CONSTRUCT), which
considers
non-linear
strain
behavior,
their
dependent
only
stress
treated
Nevertheless
of
area
the
actual
studies
looks
date have
to
advance
of
an
to
forward
performance
time
excavation.
a significant
is
writer
The
versus
Path
parameters
Finite
numerical
conjunction
and
appropriate
soil
excavation could
approach.
with
technique
the
time
include
Method
obtain
with
provides
Method
which
Element
excavation
an
their work
Stress
powerful
the
hypothetical
and
an
in
this
evaluation
actual
of
excavation
TIME-CONSTRUCT.
The
soil
simple,
study.
predicted
using
a
Although
the
complex
Stress
Path
parameter
then be
effects.
Stress
the
can
a rational
be
stress
Method
input.
predicted
to
One may
Path
used
way
using
The
sequential
distribution
The
combine
Method.
to model
used
select
to
in
determine
deformations
this
of
fundamental
r/wrP/Y
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EXAMPLE
BRACED EXCAVATION GEOMETRY
FIG. 2.1.1
49
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STRESS
OF
PATHS
NORMALLY AND
P
A
FOR UNDRAINED UNLOADING
OVER CONSOLIDATED
SOIL
ELEMENTS
FIG. 2.1.2
50
- aue
PAT'
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U ES~
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4.
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CON54 LuDATioN
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STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION FOR
NORMALLY CONSOLIDATED SOIL-NO DEWATERING
FIG. 2.1.32
51
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_m 2u
3
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LLSS
- :'\-s
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STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION FOR
NORMALLY CONSOLIDATED SOIL-WITH DEWATERING
FIG.2.1.3b
52
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II
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Sk49EAQ-
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STRESS PATHS FOR UNDRAINED UNLOADING
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FIG.2.13c
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53
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STRESS PATHS FOR UNDRAINED UNLOADING
FOLLOWED BY PORE PRESSURE DISSIPATION
FOR OVERCONSOLIDATED SOIL-WITH DEWATERING
FIG. 2.1.31
54
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w
ow
DEWATER
K0
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SZD(s
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cdewoter-
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DETERMINATION OF TOTAL HEAD
-
TO EXCAVATION
SUBJECT
(19618)
AND/OR DEWATERING
FIG. 2.14
L
250 0
14000
T
3.0
5000
N
A
-
6m
2.0
20C
4000
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I3
b
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7
7'
8000
%
2000
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SC 0.
so
0
4 000 -
0
1000
3000
2000
5000
4000
STRESS PATH FOR SPECIMEN
6000
7000
0
t1
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STRESS
500
1000
500
0
pSi
Oh;
PATH FOR
2000-
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ACT!VE
N
SPECIMEN
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8000
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Stress History For Specimens
N
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1000
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FROM HENIKEL (131O)
0
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1000
2000
3000
5000
4000
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I.
STRESS PATH FOR SPECIMEN 0: PASSIVE CASE
7000
0
500
1000
1500
2000
2500
3000
0r, ps.
STRESS PATH FOR SPECIMEN
N. PASSIVE CASE
STRESS PATHS FOR ACTIVE AND PASSIVE CONDITIONS FOR NORMALLY AND
OVERCONSOLIDATED SOIL
FIG. 2.1.5
4~1
-a
EXCAV'ATtoM
0
TV
ru
N.
T>
P o It-4I
hp,, . Y
pressure
un
N
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STRESS
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PATHS
FOR EXCAVATION
IN
COHESIONLESS
SAND
FIG. 2.2.1
Flow
Flow
FILL
SILT
-SAND.-.
--
GRAVELLY'.
'SAND o
. 5
6
U,
B
-
.
-
//IA\\WI/
,
Piping of
of Fines into
Fines from
Coarse Structure Coarse Structure
-A]Movement
-
I.
FRoM CLOuG6
PIPING/SUFFOSION MECHANISMS
a' DAvI1OSoij
('977)
F IG. 2.2.2
58
t
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C
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0 2
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202
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LWIJ~H
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-19.15
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11
Feb.-
(1957)
INCREASE IN STRUT LOAD VS.
BRACED CUT
IN
STIFF
TIME FOR A
FISSURED CLAY
FIG.22.3
59
C
/2
V
K~..
1
t
t
A/o&7-HAMP7Zw VAKYEZ) dAY
(DD
'2-
V /sSA97)
/0
2.
0
0.8
__ ____
Ilt
I
Z
5-0
0
_ ___
_ ___
__ _____
/00
20
00
CYtCLE_
_
_
ILL
-ruTA
LOADING
(-)
II
I
.
2
CA S c
5
20
50
-rs '\
7.EST
VARIATION
/0
IN
COEFFICIENT
/00
CoO
4o
AFTEZ LADO 973)
OF CONSOLIDATION
FIG. 2.24
E
description
Water con!ent
SSoil
20 30 40 50
Undrained
shear strength
Unit
weight
J
/m
t /m?
3
1 2 3
-IT
IV
rS-61 ITS-62
St
S-631
S-190
T
. 5
FILL
-87
186
188-
CLAY CRUST
0
----
w
L- -L
--
-5
EARTH PRESSURE
CELLS
89
5
187
E
5
192
7
194
11
-
01
5
0
20
184
li
natural water content
: liquid limit
wp= plastic limit
w
S
V
sensitivity
z cone
z vane
121
131
141
2
Key
S - Settlement bolts
P - Piezometer
_
15 I
-14.1
--E
-15.3
=
Typical soitl data
0
5
10
Scale, m
Instrumentation details - Tdlefonhuset.
FROM DtAw'io ;
SOIL PROFILE,
0
11 1
-15
w
ON'
101
___2_
208
-3.6
81
P
p_9
z
-10
-
-5'
71
w
V+i
187
2
-112
+
-02
6
t 868
-1
-
0-
SILTY CLAY
I
------
2
5
185
1
-
------------------------ ---
EXCAVATION, AND INSTRUMENTATION DETAILS
WALL IN SOFT CLAY, OSLO
FOR A
RoTi
(97Z.)
BRACED SLURRY
F-IG. 2.2.5
61
100
0
200
50c
/00
600
700
Indr
cf
nistollation
300
ottm
is B
EARTH
PRESSURE
16
.12
*
-
10
-~ ,
,--
--P
-- T0 I
3
.
----
d
8--
o~~~N
i
*
a>r~
5.
C TOTAL FORCE
-200
041
LOCATON
T-.
0
038
E
PORE PRBECSSUR E
SUMMARYOF
.OBSER.E
--..
.PP
2---------
9
0
0
0
C
130 rC
0
.
0
2
E
-
2
1
Po'i
0
100
5-63
-'-"
SETTLEMENT-
...-
400
30C
20C
DAY
Summary
OF
Soo
60070
NUMBER
of observations
FROM 1D'tB,,Aci0
SUMMARY
F
- -
from
Ren'
Dec
1969
to
Sept 1971
(1577.)
OBSERVATIONS FOR BRACED CUT IN SOFT CLAY, OSLO
F IG.2.2.6
1
62
SI-2
T
S4
is-
+20 -
0
-
IS-2
/WAAA7AaywA
Sand
JS-3'
-20
Medium clay
layer I
P5-25 o
S4-39
-40
layerclay
s___o
WIS-1
o-25
-39
P6-52ijo
P1
S2
o-52%, P2
-60-
Soft clay-sand
layer III
-80
P3 -77;,
N -92Bl
Tif
BMf
0 -991,
+2 B
p,
2
>
(tons/m )
-
20
10
2DL
STRESS
BELOW
THE
CAES
PATH
FOR PIEZOMETER P-1
FOUNDATION EXCAVATION
F G.2.7
BOSCO SCHOOL
DON
3,
70
,,
0-0
0
12
7
20-
/
/
-5
22
/*/
N
I- 40-
W
15
a
60-
-20
*-
H
~-
-- + H
to
Stiff
ld
-+
H
C /C (3.6 M)
(.,3
50FT
Bottom of Excavation
P-_
Concrete
Wall
l80FT
Boston
Blue
10
H
STRUTS Z 12'
-1*---
bIv
Medium
100- 30
_+
Stiff Boston
Blue Clay
with Sand
Len ses
a.
H
N
Very Stiff to
10
///////
122
HARD
Y E LLOW
CLAY
/
V.
Fl LL
,3
STRUT
CLAY
B 14WF127
TILL
C
D
14 WF 103
14WF 176
WALF
36WF170'
36WF 150
36WF30
FRom 3AWORSKi (1973)
ROCK
SOUTH COVE
SUBWAY
EXCAVATION TEST SECTION
PIEZOMETER P-4
FIG. 2.2.8
Ut~~~
ao-
n
44oSDE WALLS
Mo
/ 00-
-44
-0
L&PPR L04". (a
-4
/00-
-- -Zoo
BEAM
ThTS R4jM0Y*D
- -
48-
//0 /Ole
-//0
I//0
4-
iA/Jr/AL.
ocr /969
949
86
-78
78
AFTEP, DATA FRoM .3AvOtKi
AuG
SEp
OC-r
NOV
DOC
JAN
FES
JAA.
AP1 .
AY
E
9
(1973)
-
:3-"L.Y
1970
STRUT LOAD AND PORE WATER PRESSURE VS.
TIME-SOUTH COVE
SECTION
FIG.2.29
65
z
I-i
PRESSURE
_j w
w
0
120f 0
20
HEAD
40
(FT)
80
60
A
100
FILL
-10
I-
Hd. Yet.
-CLAY
0
INITIAL READINGS (3/69)
EXCAVATION
00- -20
Stiff
Boston
-30
80_h40
FINAL
CLAY
PH-3
(4/70)
p_--
/777
N
PH-4
P5
P -(ON
Medium
-70
READING
< -P 4
Blue
-50
COMPLETE (11/69)
H
.
OF EXCAVATION)
Boston
40- -80
Blue
-90
CLAY
-__
n--P6
_____
STATiC
20
-100
Uss
K walI =Kh
I
TILL
soil
Don Bosco High School
PH -4
H - 0~"7
~
P
nu
.-
II
P-I-H
FROM ~SAWORSKI (11-7)
MEASURED AND PREDICTED
PORE
PRESSURES-SOUTH
COVE
STEADY
TEST
STATE
SECTION
F 1G. 2.2.10
66
EA
E
.
2
Open tiroe,' panel ( -0x
E
V,
Steei
[p,
.
E
~
E
-
EE E
Water conten
(%)
0
1-7 1- !-9
s/QkC
2m
density(ton/-'
B.lk
10 20 30 40 50 60 70
E
Ock beading plre
Screw type steel struts
Stee' re'erence
0-9 M
1-33m)
waling(.70NP)
2-0 2-1
Shear stre-grh (ton/m2)
24
6 81012141618
Sens;tivity
4
LL
PL
Uncor fined1
compressior tests
fIn
I
1 /one
g -_
_
3
boring
27
-_--_-_-_-_--
-
30
120
~
C,
MaxImLim winter strut
0
;
7 6 5 4
lood(ton/m rur)
3
2
1
Autumn stru load (t
0
7
2
0
m run)
4
5i5
5
A -+
Max'mum frost penetration
.. 15Nov
-25 Nov.
C-.
4 Feb.
, Isept(Before
27.ar..956
excavation)
20 Sept.
Lines of zero pore wcter pressure
F-
0
1
Distance scc'e
2
rn
TIME DEPENDENT BEHAVIOR OF TEST CUT
(Ju20Sept
? 21 Oct.
T 5 Nov.
25 NO V.
FROM WERLLM
AN[) DSAGio (1950
IN STIFF FISSURED CLAY
FIG. 22.11
67
2c Z 29 psi.
2ct= 23 psi.
w
31-0
%Le
p.s.
30-9
-
14-5 psi.
9-.p.si.
320
-
14 p-s-i.
17
31-0
--
Shear zone
15 min. test
p =30 ps
7 day test
Ct= 1 7 0 0 ps.f.
c = 2100 ps.f.
Aj 4 9.3
51 .20-8
C
A =
"rheolog;cal"
+0-6
decrease in strength
100%
ecrease due to 6")
c
80
cl
-
60-
Block
2
6
31
Water content
41 increase in
0
Aw
2015 mns. 6 hrs.
l aCy
2
5
Time to failure t
15
10
(fi scale)
20 days
c= rzor sirength, time to fcilure =15 mins.
c1zsheor strength,
tirr.e
to failure
=t
ROm
EFFECT OF
ON
STRENGTH
VARIATION
IN
OF TIME
TO
UNDRAINED TRIAXIAL
sKEMP-roej
Aus LAROCHELL1E
J%
FAILURE
TESTS
FG. 2.2.12
>
68
At-/h SAM^'
(o p~s)
5'
|
AoArxdrw*N
10
IL4
-50
oc/47
-50
L6
0
T74 1
/cc/e
/03eH
71s T S-c1roN A
i-
0.
-
lr7,
0 "*C
*5)',-i,
4
/0.
&0.
-
Se
-
/
/
O#9d7J
K
A- .e4 '/Oa0*~ cm/s,
N
K
*
r ro-.sc
//7~
-,/0
8ro
#0.
4/s/
o cr/7"5
s o pio
.$a*!
N
428I7m7
GO -
.
/L
o
/0,4 -'/Xie
GP-ay .5o7
-
C/ey A/5O7O'
y
... ,awn any,,-,,,,,
S.'leebn;
-
SO./ A1-4
r
cl"ece
See/c
-/./
7
EXCAVATION
PENETRATING
5sr SEcf/oA B
SILT:
MBTA
FRMo\
TEST
LAMBE 0570)
SECTIONS
A
& B
FIG. 2.2.173
69
0
F/LL
AMLasured Pote Pressures
x 40 feet from wo//
*
/8 feet from wo/I
/0
o
9 feet from woll on 6/1/69
Steoy S..pge
K 20-
Best Estrnoe-
Kj
S1L T
Stoic , /4s
30
x
0
40
7LL
0
/
2
60 -
3
PPESSLE' IN K/PS/FT 2
POPE
PPESSUPE
.ECT/ON A
0
Teas4jred 20 ft from
x
C
/0
M
easured
wa//
a/ong wo// //IG4/68
FIL L
K
t~J
K
k
30-
0
StOfc,
LIS
SILT
Q
40-
TILL
Steady
Seepcpe
60-
0
,
U4. 5
I
I
I
I
2
3
K/PS'/T
PPc'SLPE /N
POPE PPESSUPE
SEC 7/ON
MEASURED AND PREDICTED PORE
MBTA TEST SECTIONS A AND B
I
4
2
B
PRESSURE
FIG. 2.2.14
GANDY CLAY5,
CLAYEY SAN D5
STRUT --
H
0
71=1
":--
O.65kH
0.65KVH
K=TANz(45-/)
K, =TAN2(i5-/)
TiER-AGHi
AtN4DkCK
PE.CK
(Ie7)
TERZAGHI
& PECK
I
HTAN(+S-
(tc3(3)
DESIGN ENVELOPES
FIG. 23Ia
'PECK (1%69)
P0EC K, "ANSON A wTHORNBURN (1'314)
fP~
f(~~/(
0.s H
0.15 H
o.751
--- 4 YT-4UT
L!
H-4CFOPt N z--mg
,'~
YH-c
CLAYS
N *~oiZ'
47
Y H
'7,,,.'
0.25H
N=c
N
H
os H
0.75H
6.
0.25 H
YH -2j
ozH
N > 6 " 8, LARGE DEPTH
OF CLAY
BELOW
0
-H
CUT
TERZAGHI & PECK DESIGN ENVELOPES
FIG. 2.3.lb
TIME TO COMPLETE EXCAVATION
0 5 days
A 50 days
o 500 days
a0
0
z
0
CE
80-
50'
C04 Cm/seC
60k)
LX
0
Cl) 0
0
7VT
k =
0
Lu
EXCAVATION
Ift = 0.305m
40-
10-6 cm/sec
20 -
1.5
x
10-5 cm/sec
-I
YO~8 cm/Sec-
0
0
0
2
4
2
4
8
6
RATE OF EXCAVATION
. in
10
ft/day
FROM CI0ot-H A, OSAIMI (979)
CONSOLIDATION AT
THE END
OF
ONE-DIMENSIONAL EXCAVATION
FIG.2.3.2
73
NS. '.(&T7
-500
Imeavation
K
K Iy
Rate - 0.5 ft/day
10-8
o/c
rr
3o cr
60
r_^ ll
wall
30
-500
-500
Vro-
O"SPm
(i9T7)
ONTOURS OF EXCESS PORE PRESSURE (pof) AT THE END OF EXCAVATION.
CONTOURS OF NEGATIVE
EXCESS PORE PRESSURE
FOR TWO-DIMENSIONAL EXCAVATION
FIG. 23.30
74
Strut
K
all
W-
. 100
-2500
-ow
3o FT
40 $r
Strut
Wall
'iT
KI .
300
Cnod"ks ,,wmvbe-)
-2500
Ffw
OSAIMI (s9TT)
CODNiOURS
OF
EXCESS
PORE
PESURE (psf) AT THE ED
OF
EICAVATIO.
CONTOURS OF NEGATIVE EXCESS PORE PRESSURE
FOR TWO-DIMENSIONAL EXCAVATION
FIG. 2.3.3b
75
CHAPTER THREE
PROPOSED PROCEDURE FOR INCORPORATING
TIME IN THE PREDICTION OF THE PERFORMANCE OF A
BRACED EXCAVATION
INTRODUCTION
3.0
In
to
this chapter
the writer outlines a proposed procedure
(pore pressure
incorporate a major time effect
construction performance.
the prediction of
dissipation) in
Acknowledging advantages of certain aspects of available
Finite Element
the writer
to use both
procedure integrates
The
Marr
Method is
for this method
The basic
stress
is
equals the
the
Stress Path
is presented by Lambe and
principle behind the
the effective stress
the effective
Hence this
Path Method approach.
The most recent edition
(1979).
lead
the use of a sophisticated computer
fundamental basis
Method.
Path Method,
in a composite procedure.
a tool for a Stress
model as
Stress
techniques and the
principle,
total
Stress
Path
which states
stress minus
that
the pore
pressure.
TI
Soil
behavior is
dependent on the effective
and future changes in effective
Table
problems;
3.1
illustrates
force,
stress history
stress.
the types of geotechnical
deformation, stability,
geotechnical engineer must face
and flow, which the
in practice.
Generally, he
76
Table
must predict the performance of constructed facility.
3.2 summarizes the
predict performance
the classes
of problems presented
in Table 3.2
the steps
follows
writer
for
The method developed in this chapter by
3.1.
Table
Stress Path Method to
steps used in the
in
the
and
for force
deformation.
OUTLINE OF THE PROPOSED METHOD
3.1
This
procedure
is
each pass
improved with
solution can be
an iteration whose
the steps
through
outlined.
Actual
field performance measurements during construction can be
input
to update or
procedure is
as
adjust
proposed
follows:
Description
Step
(1)
The
the solution.
Using
computer program which
a finite element
models braced excavation
an initial geometry and
properties
(i.e.
(i.e.
input
BRACE),
initial
soil and structure
strength, moduli,
pore pressure
parameters).
(2)
From Step
(1) obtain total
stresses
(approximate).
Ac~
(3)
From Step
(2) obtain
usE(the
generated by the change
excess pore pressure
in total
stress
due to
excavation).
(4)
Estimate
u (the excess
from the altered
pore pressure
flow conditions
resulting
associated with
77
the excavation).
method
Run dissipation
analysis
condition (i.e.
one,
for actual drainage
two,
or
point
(7)
a representative
and
an undisturbed
Consolidate
in-situ
three way drainage)
coefficient of consolidation.
Estimate the percentage of
Select
if steady state
anticipated.
with estimated
(6)
flow net or other
(FEDAR) may be necessary
conditions are
(5)
A hand drawn
the
soil
stresses.
dissipation, D.
element(s) or
soil
sample(s).
specimeNs) to
Measure
prediction
the
the
estimated
coefficient
of
consolidation.
(8)
Shear
the
obtained
other
the
be
for
words
shear
sheared
second
the
sample
set
the
by
applying
procedure,
The
conditions
executed after
partially
the
first
of
stress
element.
Measure
strains 2S .
are
total
representative
apply ACrF.
under
a
In
actual
set
of
pat h
uE
tests
no drainage.
the
drained
first
tests
a nd
If
pass
may
might
a
th rough
be
required.
(9)
(10)
Using
the
results
estimated
time
determine
the
t
of
(5)
and
for
the
excavation
percentage of
of
(7)
and
the
constructio n,
dissipation,D.
Then,
AUJT~ D
4UE)
+_
1. One might use superposition as shown previously in
Figure 2.1.4
to obtain the
initial net excess
pore press.
78
(11)
to
Apply
the
consolidation
(12)
strain,
£c-
=
ES+Ee
Find;
E
This
is a convenient simplification of the
partially drained behavior.
that
the
shear
summation of
for
Later,
the
one might
drainage
the strains
Compute
same
use
to refine
a
final
stress
path
in
that
parameters
the
actual
established
contours of equal
Figure
determined
for
to
the
path
tests
with
Eva
the computer program
tests,
undrained
effective stress.
partial
stress
3.1.
From such
any element
fL
~
strain
2EV
curve
passing
level.
from
(BRACE).
strain
ratio ,v;
~
through the actual stress
Re-input
assumed
equal
be replaced with a single modulus
passing
seen
for
soil modulusE and Poisson's
Here we assume
into
is
actual,
the solution.
V
(14)
it
a partially drained stress
terminating at
can
Here
followed by consolidation are
strain
(13)
the
Measure
specimen.
soil
the
test
data
For a series of
can be plotted as
plots moduli can be
by plotting the
total
79
estimating the
stress path on this plot,
"undrained" strains and adding them to
the
estimated consolidation strains.
Check against original
(15)
reiterate procedure
total
stress
paths and
if necessary to refine solution.
Below are summarized the main simplifications and
assumptions made
in the presentation of the method;
Deformations
(1)
for an undrained unloading followed
by consolidation to a final effective stress
equal
deformations
for a partially drained
path terminating at
The actual
(2)
stress
the
same
point
stress
effective stress.
final
strain curve can be replaced with
single modulus passing
through
the actual
stress
level.
The dissipation analysis
(3)
details
of
initial pore
is not
pressure distribution.
Contour plots of equal vertical
(4)
constructed similar
consolidated
soil
too affected by
to the
strain can be
plot for
the normally
in Figure 3.1.
Obviously this method relies on a laboratory
technique
other
in
to obtain a soil modulus.
factors
influence this value.
Sample disturbance and
Another
the difficulty in correctly assessing the
dissipation.
of this Stress
However
the writer
Path Method type
approach for obtaining input for
Finite Element
testing
believes
technique
limitation
lies
pore pressure
the application
is
a rational
the computer program.
parameter studies have shown for
As
supported
80
excavation, notably
the Palmer
soil deformation or stress
the
greatest
and Kenney (1971)
strain modulus
influence on the
solution.
is
found
study,
to have
One of the proposed
method's main objectives
is to obtain and use
in a way which considers
the effect of pore pressure
dissipation.
the
this modulus
81
TYPE
EXAMPLE
Predicted
Para meters
Needed
T
U, ()h
F
Forces,E
Wall
s,E
H
Deforma-
c
H
v
Off-Shore
w
Au with
cycling
Structure
FS
F
FS
Dam
Stability
Natural
Slope
q, ht
Flow
-- -
Flow through Dam
underprtce
from
Stability
of soil
particles
Lambe and Marr
GEOTECHNICAL
k
(1979)
PERFORMANCE
TABLE 3.1
82
Step
(1)
1
2
3
4
5
6
Force and deformation
(2)
Stability
(3)
Flow
(4)
Estimate flow
Estimate location of
pattern
surface of minimum
stability
Select average element or select several elements
For selected element(s), determine stress paths for:
(a) Geological history, i.e., past; and (b) design life
of structure, i.e., future
On soil existing at or near selected elements in field situation
Run tests along stress paths determined in step 3
(Orient samples for tests same as in field)
(Use field permeant in flow tests)
Obtain permeability;
Obtain strength or
Obtain stress strain
Measure any
strength parameters
or modulus
movement of
soil fines
Determine flow net
Factor of safety =
Force = f(stress) or
average strength/
f(modulus)
average shear stress
Evaluate stability of
Average shear stress
Deformation =
soil to flow
from: Force polygon;
f(strain or)
or elastic analysis;
f(modulus)
or frnite element
analysis; or
stress paths
Estimate stressstrain pattern
from Lambe and Marr
STRESS
(1979)
PATH METHOD
TABLE
S0
0
w
3
I
Il
I
--7-EN-
2-------
ba
62
I
--I
b
1
a , , , 3
I
--
0.70
=.
0.
H -t
1
~1*~
V
2
00~
w~
%
0.071%
-~
2
2
3
5
2=
LAN|LLMNILLAS CLAY
CONTOURS
(kg/cm
2
)
FROM LAMSE
OF EQUAL VERTICAL
1 WHrTMAW (1963)
STRAIN
FIG. 3.1
84
FOUR
CHAPTER
ILLUSTRATION AND
OF THE
PROPOSED
A
TO
To
outlined
prediction
of
The
Japan.
29.5
take
the
Specifically,
meters.
and
the
loads
stage.
The
excavation depth
at
stage
this
is
is
of
depth
to
excavation
a critical
for
a
Tokyo,
in
attempt
will
writer
deformations
predict
make
a design
to reach
years
two
the
drained
and
currently underway
is
over
partially
a braced cut
of
performance
illustrate
the writer will
3,
chapter
in
excavation
to
scheduled
the
develop and
to handle
the method
of
conditions
approximately
meters.
It
is
emphazized
the
good
stress
history
of
information pertaining
below 45 meters.
static
or
lacking
Initial
non-static)
have
is
deposit,
the
soil
available
the
that
Particularly
insufficient.
the
STUDY
CASE
to
a vehicle
as
serve
application
on
PROCEDURE
INTRODUCTION
4.0
20
APPLICATION
to
the
character
groundwater
not
been
(1)
stress
(2)
u.
(3)
limited
history
soil
(oedometer
samples
and
as
measured.
tests)
tests
a
the
of
conditions
information:
missing
well
is
information
adequate
as
data
test
lack
of
soil
(i.e.
Summarizing
85
is to
of this chapter
the main purpose
Nevertheless,
its
illustrate the proposed method and demonstrate
In
applicability.
the
available test and boring data.
4.1
PREDICTION
TYPE OF
In Lambe's
(1973)
Rankine
lecture "Predictions
Engineering", Lambe classified predictions
A
Before
event
---------
B
During
event
Not known
Bl
During event
C
After
event
Not
C1
After
event
Known
The
prediction
writer's
A prediction
prediction.
underway
currently
writer
stages
AT TIME
OF PREDICTION
MADE
TYPE
did
prior
would
Known
will be
of early
fall
into
a
known
classification
stages
of
A
the excavation
the class B category.
not have measurements
to
Soil
in
follows:
as
RESULTS
WHEN PREDICTION
PREDICTION
The
made using
the process a prediction is
of performance of
these
prediction.
PROJECT DESCRIPTION
4.2
4.2.1
The
facility
General
excavation
for
the
is
for construction of a pumping station
Nakagawa
Sewage
Treatment
Plant
in Tokyo
86
and
is
designated
designed
wall.
79
as
Plan
meters
internal
mediate
deep
dimensions
long
and
vertical
Figure
locations.
4. 2.2
Cons truct
pertinent
4.3
4.2.2
Soil
Limited
profile
preliminary
of
silty
clay
extending
Below
these
sandy
clay
soil
below
this
from
a
approximately
wall
columns
of
plan
details.
to
wall,
have
excavation,
25 meters
the
schedule
this
inter-
supported
by
lime
soil
has
view
and
Also
shown
been
cross
secton
are
recent
for
construction
and
period.
lies
soil
data
intensely
sandy
silt,
to
a
stratified
fine
depth
a relatively
indicated
sands,
of
that
the
deposits
clayey
of
silt
approximately 45
dense
stratum
of
soil
sand
and
meters.
and
layers.
cohesive
are
from
pile
Conditions
soft
of
are
pipe
is
CONDITIONS
consists
plasticity.
filled
system
Schedule
during
relatively
The
support
bracing will
the
shows
depicts
events
SUBSURFACE
4.3.1
ion
wide
derived
upper
4.2.1
concrete
excavation
lot
construction
boring
Figure
the
Within
the
excavation
meters
support
of
these
of
Cross
piers.
stabilization
The
braced,
52.5
dimension.
executed.
B.
a cross-lot
concrete
showing
site
Blow
soil
counts
typically
depth
deposits
to
are
of moderate
(blows/30cm) in
less
than
10,
approximately
50
the
gradually
at
to high
top
30 meters
increasing
a depth
of
50
meters.
87
Groundwater
4.3.2
Groundwater level
is encountered
at
1 to 1.5 meters below ground surface.
approximately
coincides with depth
Elevation on the boring logs
(i.e.
5 meters, elevation = -5 meters).Unfortunately
=
depth
in borings
sea level)
datum (i,e.,
to which
not known
it
is
these elevations
are referenced to.
Unfortunately
conditions
site.
at this
in this
assumed
nonstatic groundwater
to verify static or
available
study.
groundwater
Static
It
55 meters
long term pumping
below the
ground
surface.
layer was ultimately reduced
static
(1968)
are
that
a
at
that pore pressures were
Kawasaki City Site revealed
to
conditions
should be noted however,
previous work in the Tokyo area by Lambe
non-static due
are not
initial pore pressure data
lower acquifer
from the
The total
to -5 meters.
head in this
Therefore
the
initial condition assumption may be in error.
NAKAGAWA PREDICTION
4.4
4.4.1
Initial Model of Field
Situation
Following the steps of the
3 the writer
limited
computer
selected an initial
preliminary soil data.
developed
to model
program.
closely model
outlined procedure
this
soil profile
A finite
excavation using
based on the
element mesh was
the BRACE
The mesh geometry was organized
excavation and bracing levels
simplified soil
in Chapter
stratification.
as well
III
to
as
Areas of anticipated high
88
stress
concentrations
modeled with
finite
is
smaller
element
a
detail
of
excavation
to
the
and
Linearly
the
mesh
initial
250.
were
as
to
III
Run
and
for
This
of
us ed
Poiss on 's
cohesive
fie ld
the
run
the
situation.
for
employed
will
be referred
using an
t
o a value of
th e
Etx
ent ire
0.40
and
0 .45
of
co hes ion les s
and
4.4. 2
were
model
Ratio
are
and
sh owing
zone
rough ly
to
wall)
Figure
4.4.1.
obtained
w ere
corres po nds
were
values
wall
to
profile,
s tra i n moduli
Values
75 which
initial
to model
analysis.
A.
adjacent
in Figure
levels
These values
selected
The
shown
are
bracing
Input
deposit.
elements
excavation
BRACE
equal
/St=
e lements
e lastic stress
henceforth
E ,/W
(i.e.
s 0 ils,
respectively.
4.4.2
-Stress Paths
To
check
A)
(Run
the
selected
in
Figure
stress
paths
unloading
of
near
paths
path
the
for
might
excavation.
the
less
become
extended
simpler
were
plotted
on
both
the
element
and
elastic
the
No.
for
the
ed,
although
initial
and
final
extension mode
of unloading.
for
the
are
shown
The
extension
and
categoriz
the
within
analysis.
wall
345),
analysis,
diagrams
paths
and
exc avation
III
p-q
stress
compre ssion
Within
be twe en
behind
total
behind
e asily
Analysis
BRACE
linearly
the
III
initial
expect
(e.g .,
wall,
BRACE
the
these
this
illust rate
one
the
e lements
Severa 1 of
4.4.3
of
paths
s
"average"
excavation.
Initial
re s ults
stres
total
from
at
the
soil
total
type
bottom
elements
stress
a
s traight
points
indicates
89
4.4.3
Laboratory Test s And Revised
Soil
Profile
General
Five
"undisturbed" 1 meter
Shelby
tubes
to
excavation
the
stress
path
and
limit
index
(mechanical and
supplement
Visual
Results
of
one
at
addition
consolidated
the
and
above,
Soil
Classification
to
4
the
path
6 combined
executed
information
torvane
by
writer
for
tests,
sieve
by
the
10
analyses
writer
to
soil
conditions.
tests
were
also
Mr.
results
adjacent
on
undrained
tests
borings
anisotropically
stress
were
supplied
compression
also
all,
and
unconsolidated
were
of
triaxial
Matthew
six
performed
made.
test
Southworth.
isotropically
in
a
Japanese
lab
obtained.
Table 4.1
summarizes
classification of the
through
A.6
for
combined
the
tests,
available
MIT were
to
In
triaxial
hydrometer)
classification
performed
In
the
available
at MIT.
undrained
from recent
samples
were made
testing
consolidated
Atterberg
7 jar
long, 8 cm diameter brass
in the
plasticity chart
the
index
tube and jar
appendix give
sieve analyses.
.
properties
samples.
c omplete
Figure
Atterberg Limit s plot
and
Figures
grain
4.4.4
near
visual
size
gives
the
A -
A.1
plots
the
line.
90
Tests
Path
Stress
stress
"undisturbed" samples
In
order
would
predicted
3 was
for
flow
Consequently
1o w in g
(1)
the
field
in
Based
it
on
the
would
the
testing
silts.
that
changes
of
that
in
writer
Chapter
time
construction
dewatering
is
to
due
consolidation
within
particularly
occur,
the
inevitable.
of
consisted
procedure
the
procedure
the
length
assumed
was
construction
the
3 steps.
envelope
undrained
to
the
via
This
Pat hs
from
tes ts
were
BRACE
of
loc al
stress
were allowed
decrement
of
Applying
a
simulat e
applied
change
post
coefficient
Unfortunately
no
III
to
Run
failure
the
of
integrit y
trends of
t he
reflects
procedure
pressures
the
situ
extension
or
( define
envelope
failure
subs tantia 1 zones
to
in
estimated
the
ompression
w hile maintaini ng
sample).
The
to
state.
Shearing
Stress
sampl es
the
Consolidating
unload ing
(3)
clayey
occur
conditions
stress
(2)
and
stress
where
excavation
sandy
the
project,
this
of
the
four
for
the writer
simulate
employed.
altered
fo
to
by
executed
tests
path
of
results
illustrate
4.4.4d
through
4.4.4a
Figures
indicated
A w hich
yielding
Pore
controlled
for each
stabilize
stress.
in
pore
shear
pre ssure
( back
consol ida t ion
and
pressure)
measure
of con solidation.
tes ts
were
performed
whe re
negative
91
excess
pore
pressures
were
this
situation
is
This
is
because
mainly
dewatering
was
not
was
the
initial
computed
to
be
plan.
pore
pre-shear
likely
occur
the writer
assuming
a
to
in
static
assumption
field
to
in
the
the
as
well.
assumed
deep
that
knowledge
field,
triaxial
pressure
although
learn
sufficient
for
pore
the
later
distribution
stresses
dissipate
originally
implemented,
pressure
this
to
Not having
effective
Admittedly,
allowed
this
of
the
initial
tests
were
conditions.
may
be
in
values
of
coefficient
error
for
the
actual
case.
Coefficient
Table
of
4.2
Consolidation
summarizes
consolidation
computed
consolidation.
Both
methods
were
used.
yielded
type
III
time
for
this
type
the
100%
of
change
A.14
plots
Revised
Soil
Based
results
these
on
of
prediction.
The
curves
plot.
of
show
for
both
pre-shear
root of
small
load
(Ladd,
time
and
for
difficult
log
time
to
writer has more
square
root
of
typical
the
square
triaxial
root of
the
from
confidence
data.
time
often
and
obtain
this
CV
time
ratios
Thus,
time
post-shear
log
increment
1973)
was
and
Figures
vs.
in
A.7
volume
tests.
Profile
the
the
borings
square
consolidation
reliability
through
from
of
recent
tests
run
a revised
The
profile
soil
at
soil
is
borings
MIT on
the
profile
shown
(October
in
samples
was
1979)
taken
constructed
Figure
4.4.6.
and
the
from
for
the
Strata
92
below 45 meters was
inferred
from older borings
in the
same
general area.
in the
The strength profile shown
for
this
The selection of
extension and compression unloading.
simple profile was
(1)
influenced by:
available undrained strength data -high
Su/
T,
values determined
(to be discussed
from triaxial
stress history
missing and would help put
perspective.
Other
such data
factors
such
unquantified effects
deep deposit,
the
Su/T-Y
(2)
of
lack of better
the writer used
tests run at MIT,
in
and
strain
the
stablization of
strengths.
information on this
strength data
selecting the
from
lower values of
to represent the deposit.
Limitations of
the
BRACE III computer
BRACE III
is
materials
that may be
use
the lime
increased the test
Because of the
tests
data is
as high
rate used in CIU compression tests
soil may have
although
later)indicated some over-
, useful
consolidation
selected
figure was
limited
--
in the number of soil
input.
the maximum number
different moduli at
program
the
(20)
The writer elected
of materials
"cost"
to
to model
of assuming a simple
strength profile described by two values of the
ratio
Su/0
0
o.
The CIU compression
tests
plotted with the triaxial
shown
in Figure 4.4.7
tests performed at MIT.
are
The wide
93
of
scatter
attributed
of
time
applied
is
high
a
as
tested
give
because
at
ra te
source
of
the
are
longer
increments
shown on
as
which
time
Figure
during undrained
Consequently
Skempton
extrapolated
the
chart.
the
octahedral
effective
words
retrieved
for
strengths
equalize.
path
it
per
pore
took
This
is
tests
a
increment,
to
pressures
shear.
a
First,
strengths
series
of
correction
for
tests
associated
with
the
were
the
based
sample
obtained
on
depths
by
insitu
stress.
ocT
In other
4.4.5)
the
per minute most
th at
i ndicated
the
Similarly
st ress
stress,
applied
strength
to
stress
(Figure
un drained
higher
writer
from each
estimating
of 0 .5%
+ 5 minutes
(15
shear
showed
dec rea se.
allowed
controlled
significant ly
samples
an d
to and
increasing
By
Laroche 1le
r ate
not
the
at wh ich
will
strength
por e pressures
pressures a series
error.
and
can be
consoli dated
w ere
a strain
tests
CIU
confining
strain
performed b y the writer
the
of
unrepresentative
subs tantiat ed by
equalize
Ja panese
depth
Skempton
th e measured
tests,
likely
given
also
fai lure
to
2.2.12),
CIU
The
the
range
wide
from a
at.
sheared
from
the
to
samples
was
strength
for
from
3
example,
a
depth
if
of
two
10
undrained
meters
were
tests
of
sheared
at
94
consolidated pressures of
5 TSM and
10 TSM, and
FOc-r in the
6.3 TSM the approximated strength was extrapolated
field was
following fashion:
in the
strength was then reduced by 20%
This
excessively high strain
CIU strengths as well as
corrected
data
from the
good
for
the compression
of
consolidated Kawasaki Clay
from Ladd et
P.I.
higher
equalling
two is
the
tests have
the strength
comparison, undrained triaxial test
In
test
compression tests.
in the
measured
The extension
tests.
equalling approximately 50%
strengths
other triaxial
the
The agreement between
MIT tests.
the
Table 4.3 summarizes
rate.
for the
to correct
.445 and .225
al
for
(P.I.
data on normally
= 40 + 10%)
(1965)
with a slightly
show values of
s
compression and extension
respectively.
Although
indicates
define
because
the
is
showing large Su/:,
0
study the
ratios
probably some overconsolidation
stress history data is
degree of preconsolidation.
of the
assumed to
for
that there
28 meters,
18 to
this
the strength data
lack of sufficient
strength for
data,
not available to
As previously stated
for the
agree well with Ladd et al
purpose of
the undrained deposit will be
increase constantly with depth equal
compression and 0.22&,o
from
for extension.
(1965)
although
to 0.43 V,
These values
they may be
95
slightly conservative values in
of test data
the light
available from 18 to 28 meters.
Contours of Equal Vertical
on the available
Based
vertical
effective stress
stress
CIU and CAU tests, plots of equal
Figures 4.4.8a and 4.4.8b
strain were constructed.
show contours of vertical
the
Strain
paths
path compression
strain on a p-q plot
for
the CIU tests.
tests TC-1 and
and show reasonably good agreement.
the
two
stress path
tests TE-1
drawn through
The
two
TC-2 are also
For
plotted
extension unloading
and TE-2 are plotted
on
Figure 4.4.8c and estimated contours of equal vertical
strain are averaged
These
through these effective stress
plots will be used to extrapolate
loadings
4.4.4
at any depth
Revised BRACE
paths.
strains for various
to obtain soil moduli.
III Analysis
for Partially Drained
Conditions
A.
General
As
previously stated,
this
prediction will
address
excavation when it has attained a 20 meter depth.
reason for
selecting
of Figure 4.4.9.
this depth is
This
figure
profile and the Nakagawa excavation geometry for
excavation stage
(depth =
bottom stability due
One
illustrated with
shows a simplified
19.5 meters).
to uplift becomes
At
the
the help
soil
the
sixth
this depth,
critical.
A
simple
computation for
the geometry
critical depth,
ZCR for equilibrium of the soil mass against
uplift;
in the
figure
determines
the
96
-Z br
-
45x
I.
-
at
45
excavation
this
and
meters
Consequently
III
runs
final
to
where
B
Run
force
of
safety
is
this
equals
prediction
will
bottom
instability
is
C are
made
for
stresses
updated
the
zero
is
downward
force
one).
for
treat
a depth
the
loads
and
just
prior
to
new
BRACE
Two
imminent.
from
For
prediction.
this
previous
the
run
the
the
are
used
obtain moduli.
B.-Computation
of Partially
Drained Moduli
partially
drained
moduli
incorporate
consolidation
strains
in
relation:
The
and
upward
stress
effective
anticipated
and
C
the
depth,
be
to
deformations
depth
- C4-5-1-S9 lO
the
factor
the
(i.e.,
xu)Y'
2.1MIETERS
~/cm
At
(2-
w
h
the
both
undrained
ere:
w h e r e:
ET =
1)
Undrained
Shear
Using
linearly
selected
the
terms
of
and
p-u 0
elastic
50
tabulated
and
o=
-
E
AL. VO&..u.MET
IC SnTrA
W
Strains
approximately
excavation
in
TiA^L STRAW
vCn
-crA.
q
BRACE
elements
the
for
values
the
III
RUN
inside
of
initial
the
writer
and outside
total
and
A,
stress
sixth
of
the
change
excavation
97
stage.
the
(Table 4.4 shows such tabulated values of stress for
final BRACE
constructed
III
RUN C).
Total
from these values.
stress
paths are then
Using the appropriate
of strain contours,(see Figure 4.4.10)the
total
stress
(minus the static
pore pressure) can be superimposed
undrained
can be
strains
the estimated effective
2)
plot
path
and the
scaled off between contours along
stress
Consolidation Strains Due
path.
to Dissipation of Excess Pore
Pressure within the Excavation
Given
the
the final effective stress
undrained shear,
shear
(typically negative
subtracting
stage
from
the value of
estimated using
excavation
lateral
pore pressure ~u.
in this case)
(p6 -
the value of 'p.
The average
the
the excess
point established by
u)
can be obtained by
for the
Refer
sixth excavation
to Figure 4.4.10.
degree of consolidation for
one dimensional
consolidation
the
wall
drainage.
impermeable
is
likely
The Terzaghi equation for
dimensionless time
factor Tv
due to
this geometry
theory.
to
Within
inhibit
the
is;
CVt
V
For a depth
factor within
(a)
H
of excavation equal
the excavation is
C
3 x 10
-3
to 20 meters
the
time
computed using:
'
c-wn/sec-nd
selected as an average value
from the stress path
test data
(b)
t :.St
5
8inoriths
is
computed from
98
to represent an average
Figure 4.4.11
unloading similar
settlement
time
Whitman p. 414
for
The
drainage
factor
path
procedure used to compute
embankment
This
0.05
for
For a linear
distribution of excess
approximately
observed
within
the
verti cal
any
of
depth
or
degree
of
pressure
pore
dissipated.
to
due
be
to
added
for
estimates
This
to
plot
pr ess U re.)
value
the
surficial
or
belo w
the
is
posit ive
to
excess
a one
pore
exc es s pore pressure
for
the
bottom
of
the
Uz would
be
derived
the
distribution
specific
in it i al excess
ta bu late d
excess
also
indicates
a c tua 1 initial
t he
pressure
the
ac tua 1 nega t i ve
th en
and
Having
approximate
mult iplyin g
t i me s
pore
which
12b
Z vs.
of
By
t he
4.4.12a.
nega tive
4 .4.
negative
element
Uz
of
this
of
linear
(1977)
Figures
r e present
dissipation
one
Osaimi
u ses
(Ide all y a
t o
reasonably
dissipation
disc ret e
constructed
excess
by
dissipa tio n
excavation.
and
to be
excavation.
pressure
negative excess
of
s tudy
the writ er
of
pore
from Figure
dimensional
degree
the bottom of the
% obtained
dist ribution
drainage.
stage of
2
the
pressure
this
of consolidation
considering
Lambe &
consolidating
average degree
excava tion
the
at
the
assumes double
for
yield an
soil
for
construction
will
(see
loading
vneters
LS
..
2 =
-
length
then equals
the
for
1969)
cohesive layer.
time
the
HA = (45- L(.s)
(c )
The
to
time
excess
(Table
por e pressure
shal low dewate ring
within
the
pore
pressure
4.4),
later
dissipated,
excavation.
99
The excess pore
be
pressure due to
shallow dewatering can
analyzed using Figure 4.4.13 for
level
a change
at one drainage boundary only.
in piezometric
This case also
experiences double drainage and therefore the
time
will
dissipated
be the same
as previously computed.
excess pore pressures are
computed
for various
obtained using this
depths
and elements
The summation of Au, + 6u
dissipated pore pressure
and/or 4.4.14b based on
the
series of
strain can be
path
stress
The
=
(AuD).
consolidation from
volumetric and vertical
extrapolated for a given
depth.
Since stress
tests with dissipation of negative excess pore pressure
were not
run the plot in Figure 4.4.14a shows
for
case.
this
strains
due
are not
likely
and
and are
Using Figure 4.4.14a
the post-shear
tests,
figure
Au, gives a net value of
in TSM.
path
factor
Since
to be
in the zone
likely
in pore pressure
recompression stage
(3)
is an unloading problem,
to dissipation of negative excess
therefore are
changes
this
to have
the
pore pressure
of primary consolidation
a similar
(but opposite in
of the
inferred lines
stress
relationship to
sign) as
the early
path tests.
Consolidation Due to Pore Pressure
Dissipation Behind
the Excavation
The steel pile wall
steel
interlocks between
prevent
leakage.
is
assumed
the
to be impermeable.
piles have been grouted to
The
100
Below the
lower silt
remain constant
access to
and this
layer the
stratum is assumed
a distant source
Given these
total head is
of groundwater.
assumptions, dewatering due
to shallow
pore pressures
the wall.
The
stress
organic
silt
path
has
test TC-1
that
the upper
of consolidation
cm /sec.
doubly drained stratum
20 meter
indicates
a coefficient
approximately 7 x 10
this
to
to have free
pumping within the excavation will not affect
behind
assumed
for
of
Computing a time
the time
factor
for
associated with the
deep excavation we get:
T .0 1
and from Figure 4.4.12
U(k 12 */
A'VG
similarly for the
lower clayey silt we
compute
.03
A'/G
Continuing with
used
for within the cut,
tion and added
of one dimensional
strains are
to the undrained
contours of equal
(4)
the use
strain
plots.
estimated
theory as was
for consolida-
strains obtained
from the
See Table 4.4.
Contours of Moduli
Contours of moduli can
finite
then be
element grid using the
constructed across
tabulated values
for
the
the
101
discrete
elements analyzed.
contours
of moduli in
moduli
for
Figure 4.4.15 shows
tons per
square meter.
the granular layers
the
Stress
above and below
the cohesive
soils were estimated using empirical formulas based
count
(Mitchell and Gardner,
for granular soils
modulus
the layered lower
in the
literature.
level
in
this
interior
secant modulus will be
BRACE III
soil materials
of moduli
computer
the
fact that
the
from this
plot were
computer program by
substituted
initially assuming
finite elements.
Total stresses
to improve the
in Figure
The final Run C was made using Fig.
4.4.16 and
20
The current version of BRACE III will handle a
of 20 soil materials.
Ideally zones of soil with
similar modulus and Poisson's ratio would be contoured,
since
4.4
these values
for
the
materials
can also be estimated as
final run.
of BRACE III is
as
shown
in Table
Unfortunately, the current version
previously
stated,
limited
to how many
may be input.
Ultimately the writer observed that
Poisson's
14
from this
solution by
determining new or updated moduli as shown
maximum
the
(moduli) and assigning the appropriate values
to the
materials.
shear stress
lower.
Run B were used
4.4.16
1000 within
zone is higher and therefore
The values of modulus
into the
The
sand and sandy clay stratum was
reduced from 1650 outside of the excavation to
the excavation to recognize
on blow
1975) and compared with ranges
of modulus
in
strain
ratio will follow the
trends
in general
outlined
below:
102
Inside
Zones
a)
1)
where
the Excavation
dewatering prevails and
the net excess
dissipation will
pore pressure is positive,
tend to increase Poisson's ratio
2)
where the net excess pore pressure
dissipation will
tend
is negative,
to decrease Poisson's
ratio
Outside of
Zones
b)
1)
where
the
the net excess
dissipation will
2)
where
Excavation
tend
pressure
pore
to reduce Poisson's ratio
the net excess pore pressure
dissipation will
tend
positive
is
to
is negative,
increase Poisson's
ratio
0.49 was
Ultimately an average value of
this value at
cohesive soils,
(0.2 -
values
0.5)
modeling of soil.
the upper range
usually used
In general
case tended to dominate
selected
in
the
for
of typical
finite element
analysis
the undrained strains
in this
the deformations.
Ko
(5)
Ko =
stress
0.5
for all
soils
was selected based
path Ko consolidation data
i equation and empirical
on review of
on these soils,
the
1-sin
correlations of Ko versus P.I.
Anisotropy
(6)
To account
Christian
Also,
for anisotropic
(1971)
shear strength, The Davis and
yield criterion was used
any yielded Elements
are
in BRACE
assigned a modulus
III.
equalling
103
1 to
10%
of the unyielded modulus, depending on the
initial
modulus value.
C.
,Loads Deformations
Predicted
(1)
Stability
and
General
From the final BRACE
III run, contours of
deformation and stress are shown in Figures
is
Figure 4.4.23
through 4.4.23.
undissipated excess
a contour plot of
is
pore pressure and
to show the approximate
4.4.17
trends prior
intended
to
consolidation.
Related aspects of techniques used
interaction are
(2)
soil
the
III computer program to model
in the BRACE
structure
section.
discussed in this
Deformations
Figure 4.4.17
the deformed geometry
illustrates
of the
steel pile wall towards
from 12 centimeters
at the
the excavation range
depth.
line.
lines
at
to a
a 27 meter
from 40 centimeters
Bottom heave varies
the wall
the wall
top of
maximum of nearly 44 centimeters
near
Inward movement
the sixth excavation stage.
after
to 76 centimeters
Figures 4.4.18 and 4.4.19
at
the
center
show selected
of lateral displacement and bottom heave,
respectively.
Maximum ground surface
excavation is
20
settlement behind the
centimeters
behind the excavation.
occurring 25 meters
Figure 4.4.24 compares
104
ground surface
settlement with
Note
Peck's chart.
the uncharacteristic heaving of the excavation
settlement begins to occur at
Ground surface
face.
In
a distance of 3 meters behind the excavation.
the 3 meter wide
zone between the wall
net upward movement
a very small
point
the writer's opinion, since this
and this
In
occurs.
is contrary
to the
downward movements we would normally associate with
past
experience,
face is
lifting of
this
the way which the
in part to
due
to the nodes
applied
the upward forces
upward
is
When excavation release
interaction.
surfaces of
the excavation
the excavation heaves,
on the newly
include an
Consequently, as
sheeting elements.
simulated
the nodes shared by
to
force applied
BRACE III
soil-structure
the
computer program models
exposed
the excavation
the bottom of
the sheeting may also heave
slightly.
This behavior
intended
wall.
to allow
stiffness of
above
the
enforced by
soil
the technique
to slip behind
involves setting
sheeting equal
set
the axial
to the soil
the
level
BRACE
axial
soil
(usually
III runs
stiffness of the
stiffness.
the
to either the
or zero above a selected
the depth of excavation).
this study
equal
the
technique
This
stiffness,
is
in
sheeting
105
fixing
fixing
b ehind
method.
A ithough
the
install at i on
no
b)
ze ro
s trut
B,
of
no
the
III
Run
B
( the
m agnified
timber
wedges)
alr eady occurred
assumed
set
of
modulus)
to
(up
by
no
the
at
was
struts
1 linearly elastic
first
the
Acknowledging
C
inc luded:
of
s ing
i n itia
shee t in g movements
shims.
in
dif ficulty
s tru t
for
(or
of movement
pr e stres
partial 1y drained
depth)
th e
realistic
ts
stru
shims
s h im c rush i n g was
Run
revised
of
C
fixing
ion.
used
Run
imple-
level
for
employed
of
latter
the
more
a
interact
final
crushing
Al th ough
Run
the
p ercentage
a
be
evidence
prestressing
a)
as
in
may
options
Input
III
BRACE
in
occurs
not
anal yses
structure
soil
t he
modeling
w i th
III
BRACE
is
Therein
approach.
face
was
directions
both
i n
node
ement
technique
this
current
the
in
settl
excavation
the
directly
mented
more
that
indicated
directions
applied
and horizontal
vertical
in both
node
by
comparing this me thod with
the writer
the
made
II I computer
A BRACE
the horizontal direction.
study by
is
strut
the
node at which
the
is
installation
strut
of
Simulation
to
the
crushing
two
showed
runs
large
A
and
firs t
using
the
inward
1 meter at a 20 meter
of
crushing
this
The
50%.
Run
error,
the
the
of
final
s hims.
BRACE
Unfortu-
106
are
experience
or knowledge
the
(3)
drawn
usually
parameters
input
related
engineer's
the
from
in
performance
actual
of
of bracing
function
the
of
selection
The
details.
a
states,
(1973)
Jaworski
also
are
level
excavation
the
above
Movements
as
excavation.
this
for
details
and
techniques
shimming
and
prestressing
actual
the
of
knowledge
have
not
does
writer
the
nately,
field.
Lo ad s
stresses
lateral
in
negative
lower
level
factors.
to
The
this
can
struts
early
for
stages
convex
tendency
back
to
the
load
unusual
struts
While
result,
is
lack
is
the
top
of
from
the
excavation
for
This
stages.
loads
shifted
probably
Jaworski
of excavation
of
negative
of
struts.
the
in
least
at
distribution
away
strut
negative
a cantilever
as
a non-prestressed
two
total
and
attributed
be
prestressing
of
bend
upper
Consequently
struts.
The
excavation
load
the
indeed
wall.
the
to
is
later
during
the
a more
by
displacement,
sheeting
behind
typically behaves
sheeting
followed
loads
since
Furthermore,
the
strut
lack
the
to
part
the
several
in
values
shows
4.4.25
Figure
strut,
upper
to
the
in
as
result
that
lower
of
one
prestressing may
notes
give
would
illustrate.
load
a
the
four
of
the
several
contribute
to
five
107
sheeting
elements
required
to accurately
between
strut
model
levels
the
Otherwise,uncharacteristic
forces may
be
to
three
levels
sheeting elements
in
this
were
strut.
used
Only
between
two
strut
study.
for
Stab il ity
4.4.26.
cases
basal
where
sta bility
indicat in g
meters.
Also
support
For
For
ana lys is
made
ity
an
note
stabili
columns
area
of
the
is
along
the
a t
that
for
z ing
e ffects
bot tom heave
Eide
in
would
section
both
excavation,
be
the
level
the
of
any
concrete
The
13%
used
4.4.4A
analyses
of
shown
recall
excavation
the
assumed
as
comparison
n eglected.
0f
d imensions
(H/B< 1)
a ppr 0 ximately
bo t tom
th e Nakagawa
strength
and
H/B> 1.
p iers have been
of these
view
Bjerrum
instabil
beneficia 1,
Terzaghi's
shallow excava tion
for
Figure
for
an excava tion of these
analyzed using
typically
analysis
in
the
sheeting
Stability
4.,
is
to
be
sheeting
behavior.
transferred
may
of
plan
area
the
plan
excavation.
the
failure
average
surface
can
be
estimate d by:
(1)
selecting
the
several
assumed
average
failure
elements
surface
along
21
108
determined
equation
The
4.4.26
extended
time
open
excess
negative
the
within
strength
decreases
value
drained"
below.
used
"
This
5=
0
is
strength
Factor
Hence
used
is
where
concept
into
input
c is
of
the
for
substituted
the
in
soi
swells
H
the
the
equation
of
the
comp monl y
undrained
c;
simplification,
-c/B
"I5=
if
it
0"
is
approach
used
for
and
the
1
Safety
a
"partially
instead
Su,
the
of
soil
n et
outs ide
elements
the
or
in
of
dissipation
as
Ter zaghi
excavation
majority
actual
the
method
of
Although
the
time
with
analysis
stability
shown
for
increases.
content
water
Safety
Consequently,
cut.
the
elements
the
for
and
the
this
a
in
pressure
pore
excavation
of
which
for
resulted
has
point
input
and
Factor
Figure
remains
of
for
star t ing
path
(2)
strengths
the
average
(4)
in
b ased
element
stress
effective
final
the
from
loading
failure
assumed
on an
each
for
strength
selecting a
(3)
dissipation
pressure
of pore
effects
the
including
paths
stress
constructing
(2)
is a convenient
this
case
the
109
Factor
of
Safety may
Figure
meter
4.4.27
stage
and
stress
paths
4.4.28
and
estimated
shows
the
excavation
"average"
these elements
average
from
unconservative.
several
for
an
be
the
strength
stress
geometry at
elements.
have
been
selected
paths
the
Several
plotted
from
in
20
of
the
Figure
strengths
is
8 TSM
(refer
safety
using
this
to
Table
4.5).
The
Using
r esulting
the
same
29.5
mete rs,
some
erro r
the
s tres
is
strength
the
s paths
as
strength
does
assumes)
and
depth
probably
well
not
the
of
for
computed
involved
different
is
factor
the
final
factor
in making
of
the
"average"
as
the
strengths.
equal
factor
a
of
constant
safety
overestimated.
excavation
safety
is
elements
In
(as
for
is
depth
1.1.
1.6.
of
Al though
extrapolation be cause
this
for
method
will
other
the
the
be
words,
Terzaghi
full
29.5
so lut ion
me ter
110
NORTH
) &cnii
80-' M
APPROX. 4LOF
CROSS LO T BRACING
-i-I
3.25
0
'-RIN
2-1
IK?~
-
6~
16
Jz54
W"
ii
I
19.2SM
6
*
6
6
K
6~6
I
9
U~TYTI
TI
1-2.N
o1
34-75M
3.25
7.01 9.0 1 9.0 1 9.0 17.5
80
3.2
5
6- 15 7
5.5 7-5
t
3.25
1.52 M DIA.CONCRETE
FILLED STEEL PIPE PILES
2-5 M DIA.VERTICAL
SUPPORT PILES TO
DEPTH OF 55 M. (TYP.)
PLAN VIEW
50-5 M±
, 15M±I , ,
ZONE A
-0
I
if
-- 10
"*/'-*"jjll1l1j
(.4
-25-
w
a
I
-40
50
L60
M C/C)
0.4M AUGER HOLES
-20
-30
W f
(0.7M C/c -ALT 14M
AND 25M DEEP HOLES
.14-
w
15Mt ,
VZONE A
, ,
ZONE B
STABILIZED WITH
LIME
L
-25
,-*
2
CAST-IN- PLACE CONCRETE PIERS
FOR VERTICAL SUPPORT COLUMNS
CROSS
SECTION X-X
PLAN VIEW AND PROFILE OF NAKAGAWA SEWAGE
TREATMENT PLANT EXCAVATION - SITE B
FIG. 42.1
SOIL
)RIVE STEEL PtLE WALL
5TAB i LlZ.
- 1
I
.
,
,
i
I
I
1978
C6NCRETEF
L'
PIER 5
I
I
I
II
I
1979
EXCAVATION
6. o
-03.5
STAGES
-14.0
1980
-
I
-20.0
M ETERS)
-e3.0
1991
SITE
I
1990
(ELEVATIONS
-rr.0
3.0
-
B CONSTRUCTION
-
0-
29.5
193
SCHEDULE
F IG. 42.2
38
0-
ift,
4--7q
G07
SAND
350
~s
~ -V
--
5-04
Wo
2
ti-i;
2ZZ
tr
g-3
0
.=W
4-1
32
4-0
30
3o
97
'4
4-9
,7
Ci
4
38
4
'I
go
41
SAND
a
49
489
28
'3
73
-T
-
4U.
37
45
11)
1
4o_
4) -35'
SANDfl
Cp
sf
493
,A4
-
=L35'
.3Z
-J
9
44
'9
*
I.,
4I
N
'3
I.
N
.7'
54
44
'I
2
t4-
9e'
0
'4
70
4-3
25
3-
8
95.
/
'9
*
2
4
5-4
4 0)
I"
7
f.
'4
C
'40
8
3
4-
" -
4821
4-7
9+'
-
30-
60
2,3
I
30
49'
495
44
V20
50
s'l
'7
4ii
497
SILT
50 -
"7
G.
(-7-
"3
5,01
so
$1~L
I-
23
'9
8
244
33
0
-
^
ALL SOILS: Y-, =- %15-fCM E/,=75) K,=0.5
INITIAL
PROFILE AND
FINITE ELEMENT
MESH
4.I
FIG..
*
e
BACM
EXCAVfli
0
9O
srAGE
/0-
-
20
30.
40
60
I
0
II
/0
I
20
zs
I
-I
3o
DETAIL OF FINITE ELEMENT MESH
40
IN
I
I
So
o
ZONE OF
EXCAVATION
7o
F IG.4.4.2
/0
6/
*
8
6
If
tJ
z
0
I
~
i~/
a
-
I
4
4~1
/0
TYPICAL TOTAL STRESS PATHS INITIAL
ANALYSIS LINEARLY ELASTIC MODULUS
BRACE
III
FIGAA.3
115
-rMf
MP E
A
uo
MIETEKS
-
-. 9
1c30
21.4
(
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TABLE 4.1
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5.1
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o
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#8 z 73
8.i (-.2 0.37
8.7 /5-0 iz-.3 /5.9 /.g
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4.7
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-
1.52
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Z03 /Z.z +.b 70
Z7g 7.4 /5.1- /4-9 /1.3 /.Sz
1. Z S4
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4.6
Z.I 4. 4.7
39
97
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4., 7-/
a. -7 3.7 7./
QissfPorfb
r.+
l .4 /1-0
38
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.Z
2.7
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88
3.(
Z5 5 /s3 5.1
30 13
ExCE0
AtY *-C
/aU
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/.57
#0.2 -4 45
-0.
-033
£MitoR b'E 7- CapWUT-1A/Or
(
0.55
308
-/(5' 0-5-2 .317
~o.7f
aSo 333
C
-
/~
-o0S*
o-D
300
.RO5
TABLE
44
ork"LI)
Cc.
(
0
5t-
\0-1
'r"SP
FPoA ORACE 22
RSP £S'4
TEO FRop
-7Ms P*r
T
E-2 ~---
TEI
5-1
-0
S.*'
t/mri O -
w
_
1-0I
\0OI
-
-
-
15 eI
27.
-
5
10
15
D
SUPERPOSITION
ON
CONTOUR
20
25
30_
__
35
t/ma
OF TOTAL
PLOT
STRESS
OF EQUAL
PATH
STRAIN
F IG.44.10
in
TIME
0
)
MONTHS
12
24
I
-2
I
4
I
I
4
I
I
I
I
~
4
Lii
___I >~~~~___
25-
30--
I.
I
A
-
DEPTH
OF
EXCAVATION VS.
TIME
FIG. 44.11
133
0
-----
20
40
40
L__
_
_
-
0
-_
_-
0.4
0.5
Time factor T
_
__--_
_
-7
0
80
-
100
0
0.1
4.4. 12 a
0.2
0.3
TIME FACTOR
VS.
0.6
AVERAGE
0.7
0.8
0.9
DEGREE OF
AeY~Iu0
1.0
CONSOLIDATION
Ue/uo
0
4.LLA
<
42
T=
.LC4
7
77E1.
0
po 10
00 0-
-0.15
0.40
0P
fh
-
0.60
--
-
0.848--
070.90
N
1
Y17
72-&
", '7!
2
0
4.4. 12b
0.1
0.2
0.3
P-
f'% ,
-.
XA
0.4
0.5
0.6
0.7
Consolidation ratio U,
NORMALIZED DEPTH
VS.
0.8
0.9
CONSOLIDATION
1.0
RATIO
FIG. 44.12
/E
~W~qVR/N6AT
SUPPICF-11V714L
LRs FG/9.SA4Em1sU____
k zx
0
=4Z
0.5
0.1
0..4(.4 8
0.2
SLT
1.0
1.5
4
F//
2.0
0
EXCESS
3 . mrro A . L- E XcESS P. fEL.
~
A
,4
Ss5
U, Lk~~
-7.2 19--2F=
-I__
_____~~~~~~
0.2
0.6
04
____
=\L
Z35
= LLTSE~
e
14 .3-i .-.
=L
-~C
10 aoe
o.%
Tsm\
L
SAYtErs
1.0
0.8
uz
NORMALIZED DEPTH VS. CONSOLIDATION RATIO
TRIANGULAR INITIAL EXCESS PORE PRESSURE
FOR
FIG. 44.13
5
-i
slr~vss461
4.
I
3
'2
V
d)
-2
'I.)
LLi
0
0i
______
0.
-I
______
______
______
ov
.- 30
S
wI
-20
-'
;-
-/0
I
153-
I,
E/IoA
'-i,
//,)ER %SA
Tie O56
s
/ rc
1oT"
t6
U.)
-
P
3
RA-SEn
5
10
z
0.
x
i
I~
,
5
PAXh'
Nvo-r.E
-4-5-
VOLUMETRIC
STRAIN
VS
S.T:WAIj
67ED
___
I
DiSsiPAiE
DiSSIPATE -&L.(EXCU5S)
IVeRrIcA
A A.S7PA
DISSIPATION
+AU,
OF PORE
(ExCESS).
PRESSURE
F IG. 44.140
I
Zo.0
I')10.0
0.0
4
30-0
40.05 0~
J4
.o
2.0
"3.
0zoo
VOLUMETRIC STRAIN
VS.
LOGARITHMIC
DISSIPATION
OF PORE
/.07
PRESSURE
FIG.4.4-14b
w
TS^
E
CAA
t,
r~t
I
v
Z;
Z - "50 r
'05-
s -
TSAI
4-a
450
400
4-00
40oo
ooors
CONTOURS
I-
OF MODULI
-
BRACE
III
ANALYSIS
-
REVISED
RUN
NO.
B
FIG. 44.15
n
I
11
F-
,E
'T
T!5^1
,\\\\\CA
20
35o7-,400
Tsm
E
50 TTSA
40
E/000I,~
/=1650
Z
-s
TSM'
60
CONTOURS
OF
MODULI
-
BRACE
III
ANALYSIS
-
FINAL
RUN C
FIG.4416
SCALE METERS
0
0
0
020
DEFORMED
FINITE ELEMENT
00
MESH
FIG.4.417
w
v
0
0
0
0
9S
S
0
/2 C0'4
4.-
-I
SCALE AlErCRS
p
0
IV
S
/0
I
I
/6
2o
zs*
SELECTED LINES
OF LATERAL
DISPLACEMENT
F IG. 4.18
0
0
0
0
0
0
76I~
.Is
SCA4E
0
5
,o
^fCTERS
/5~
Zo
SELECTED LINES
OF VERTICAL HEAVE
FIG.4419
0
0
0
t+IXAr UM =0 . 3 /7 TsmA
MINI MUM = -12. 3835 Tsm
CONJTOUR INTERVAL - 0.900
0
I 2(
Kil
1(
11r
.317
7
7
j _I
---
/
P7
/
OVN
SCAA.E
I
00
METEkS
p
I
/0
is
I
I
2:5Z
CONTOURS
OF
SHEAR
STRESS
FIG. 44.20
C-)
MAXITMUM
-
MTNTMUM
-
0 . 235 TSM
-96. 860 TSM
UONBJR I.NTLRVRL
7. 000 TSM
+
5'-
/0
o
20
TOTPL SiGMr7
LI
is
CONTOURS
OF TOTAL
SIGMA
Z
F!G.4-21
4D
S
SC
MRXIMUM
-
e MINTMUM
0.0 00 -rSm
TOTRL SIGMAi X
-
- 74. 760 TSM
CONTOUR INTERVAL
5. 000 T-Sm
o.co
O.0o
fr.J
.Ls
-/-04-
Go
SCALE
i
05
/0
---
AfE7ERS
7
/5.
I
ZO
25.
CONTOURS
OF
TOTAL
SIGMA X
FIGA4.22
0
21.500 TSM
MH XlJ MUM
PORE PHESUPE
(LuNjDs-sipATED)
+0. 683 TsM
MINIMUM
CONTOUR INTERVAL = 4. 000 rsM
S/0
!
SCA.E
zo
rs
-AIrERS
.3
I-'
V
CU
9
)
CONTOURS
SHOWING
TRENDS
OF NEGATIVE
EXCESS
PORE PRESSURE
FIG.4423
146
5E/7-4kE/xNT
ADJACEArr
Tco
EYcAVAIO/AIS
PEC/< (1369)
V/S~TAA/CE FROMA
AMI/Uf
EAcAVrrI/0
DEPin OF
rXC4vq7oN/
0 r
IA
*
V..
PREDICTE D
I~1
LQ
//
BA CE iTI
1z
14)
7z
3 Z
=?,>FGUIe
aM-l(
4
f.0
Zone I
Sand and Soft to Hard Clay
Average Workmanship
Zone II
a) Very Soft to Soft Clay
1) Limited depth of clay below bottom of
excavation
2) Significant depth of clay below bottom of excavation but Nb<Ncb
b) Settlements affected by construction difficulties
Zone III
Very Soft to Soft Clay to a significant
depth below bottom of excavation and with
5
Nb Ncb
COMPARISON
BEHIND THE
OF PECK'S CHART WITH
NAKAGAWA EXCAVATION
SETTLEMENT
FIG 4424
73RAr'E 77T
Z=
317..
STRU7T LOA)S
-
57.7
-- ,
-
40.3
-'
+2m.
AND 9H DISTR/iBtIOAw
(w.I'' 57 T
e
Av'A
.,F (DEP
VA
4".'
rioA
/ -)
S. L .
-8.03
4
I
-0
L
'lN
~Thuo
4 -1
~0
SWAL -
60
S'o
40
ZO
/0
0
5T7xE5S
r0
/0
30
40
o0
-7r-S-l
ESTIMATED TOTAL STRESS DISTRIBUTION
THE STEEL PILE WALL
BEHIND
FIG. 4425
148
L= Length
10
Scuor
S
cuor (BAL = 1)
B/L= 0. 5
8
H
4-
0000,00
e-000", 00011-
Strip (B/IL=O)
6
k--B-.
4
0
Factor of Safety = -;
CNc
y
1
2
-3
4
5
H/B
Bottom Heave Analysis for Deep Excavations (H/B >1)B JERRUM & EIDE
(1956)
B
L/
0.7B7
H
+
/
D
H
-
W
450
0.7 B
Factor of
Safety
1
H
C Nc
y- C/0.78
Factor of
1
Safety
H
CNc
- C/0.7D
Bottom Heave Analysis for Shallow Excavations (H /B<1)TERZAGHI
(1943)
BASAL
Fr-GuGE FQO M
HEAVE
CLou44
CISC.WA1Tr
C19-1-7)
ANALYSIS
F IG. 44.26
B
iN
-50.-
T
mrmes
/7=fe
r"+
a
-=
1-r
0
r
Z r 80 sErRs
--
I-
4,
MlER
( 114
EXCA-ATlJM
-1
VTAGE
FtGiTE
EME
M4ESH .
-Aa
L- -
IA
r
represe t
-
-
J
-
2 iS
... ....-
surfoTce
-
4
36
-I
-
..
-
..
--
-4
-4
'4
3
G = Ts.*I
N
-4
544
5"
f,9,
1;;
A=
'37
/
.4'
N% x C.3
SIXTH EXCAVATION
E S. =
STAGE -
/
-
c /'
..- c17,8
I
/.5
ex .3
.
7
g
1.63
STABILITY ANALYSIS
F IG.4.427
-
-
-
DR
AlEb 8.EMAVI O
v
0
AOWiER $ANJDY LA.CY~e
/0
-
4-0.
%,TSM 0
2
/O
'ESP
f
20T'
SOXCA'4A1rof
STAGE
AStA.Akrr.. FA ItI UP
ko.0 AfC7
.-'
A.OADiAIC7
/0-
PReITAL Ld,5,#/04P
SpoE
ESITI
10
AL LIoAJ~IuG
2o
30
_
40
s--
/0
-
STRESS PATHS FOR STABILITY ANALYSIS
FIG.4+28
FL .
D[P77/| ?.-u.
g.
34
31.75
/9./
6.4
38
/2.7
3.9
4o
5.3
.76
43
3.4
z4g
U111
au,,
0
0
-3. 5
.0t
-3-1
.42
2.6
/o.'
3.6
9. z-
44.o
4J/q
P - u.
zt .f
6.IT
/-3.
0
0
a
0
-/o
0
0
0
0
0
0
//./
Aub,
0-'7
o
au,
-. 04
-. 04
0
-/1.4-
0
-. /7
-/.4
-. 7
o
0
0
si
es
0
/
*
3
/30
0
/3-
293
24's
5.0
'3.0
-/2./
o.57
OS
-
5-0
41,9
Z.0o
-1.0
(-4,
376
/7.(.
295'
"'/.?
5. 1 -' .
0 77
/Y19
f/.,
-.47
0
^-0
0t
397
4"-
4Z9
34-. C /7.,f
482Z
45t.
253
-510
Z9. 1
97
/70
-7-0
(.8
-4.3
/.'
-0.B
4A4k
08
/.
*0..6
24.-
/04
TZ.A1S
JSE0
,,F
-
^AlrE.
aR
4,JO
,
0
0
-208
0
-27.9
g
.laz
0.
0
-3/
*.3/
0
0
4
0
7.5
-U.
I
'-
0
718
Ao
/'.9
.
/
--
0
0
e
S=STREA/7)Y
MTr C TOAJS
&JE ,,V6,-O
H E 0-
4o,
AVG.
4-078.3
- 33
TABLE 4.5
152
5
CHAPTER
SUMMARY AND
5.0
GENERAL
Review
role
of
of
response,
the
i s
time
effect
will
0 ften
lead
to
for
environmen t
Similarly,
the
safe ty
of
can
be
braced
thes is
excavation,
p resents
to
intende d
of
effects
method
the
the
bet ter
pore
the
also
that
Element
effects
of
of
thi s
in
a
u rban
combine
the
soil
pressure
pore
deformations
concern
major
This
of a method
the
including
a pplication
Stress
obtain a
non-linear
etc.).
areas.
by
The
warrants
surrounding
app 1 icat ion
such movemen ts
to
of
safety
dependent
time
the
and
are
anticipated
Method
of
excavation
of movement s
can
factor
an
dissipation.
one
soil
func t ion
a
fo rmulation and
pre dict
the
and
Path
powerful
behavior
of
Method
app roach
and
consolidat ion.
The
braced
as sumption
exc avation
that
in
undrained
cohesive
soil
conditions
need
not
the
pore
s truc t ures,
particularly
pressu re
shows
F inite
inc lud ing
and
tolerated
in
workers
existing
magn itude
The
because
the
p ublic,
deformation s are
which
with
av ailable
(general
d iss ipat io n.
a decreas e
that
show s that
o f excess
influencing
conclude s
writer
excavat ions
Dissipation
major
The
behavior,
the
important.
t echnology
best
braced
the
time.
with
history
case
time
pressures,
in
CONCLUSIONS
prevail
be
merely
in
153
accepted
for
lack
model
partially
it
illustrated
is
also
be
scale
need
a
Method.
is
5.1
to
a
Plant
powerful
tool,
and
applied.
the
problems
to
on
geometries
The
such
Although
can
as
does
not
Stress
the
Path
Nakagawa
the
finite
element
the
use
it
is
justified.
method
as
applied
of
to
a simpler
One
apply
method
method
deformation.
program
Excavation,
be
excavation,
and
complex
proposed
can
complicated
element
The
program BRACE
LIMITATIONS
One
limitation
chapter
work
four
not
is
of
that
involved.
additional
that
excavation
stages
stage.
execute
and
through
fit
the
the
hand
stress
strain
test
(1970)
present
(refer
one
can
was
data.
to
and
s t udy
entire
for
model
to
o ne
must
or
curv e or
all
obtained
from
the
Kondner
(1963),
discuss
utilization
and
of
ha ndwork
5 .1 helps
it er ated
to
f or
would
be
stages
equation
modulus
undrained
for
stress
Duncan
and
of
hyperbolic
the
is
of 0 ther
stage s
hyperbolic
initial
where;
of hand
two excavation
An
5.2)
be
in
s t ag e of
Fi gure
performa nce
p roc e dure
of
one
only
data
strain
Figure
amou nt
p red i cted.
approach
amount
al ternat iv e
the
the
pre d ic t
to
work
be
to
t ime
cas e
this
a polynomial
ear lie r stages
model
for
A better
the
then
testing
In
a significant
is
compa red
performance
illustrate
proposed
there
and
unreasonable.
each
the
However,
tests
construction
to
a major
stability
for
method.
conditions
less
finite
However
Treatment
III
for
estimate
large
another
drained
applied
to
of
Chang
the
154
As
the
although
behavior,
program could easily be modified.
(1)
Large
finite element computer
BRACE
III
program
Stress
to
a
tests
although
larger
can
disturbance
test
BRACE
SUGGESTIONS
in
and
(1)
difficult
stress
carefully exe cuted
mor e value
significantly
common
than
tests
laborat ory
factors
su ch as
sample
laboratory
influenc e
significantly
make
the
prop osed
compatible
are
need ed
dimension
FOR
soil
area
by
Osaimi,
the
program
to
method
( i.e.,
ha nd 1 e
input
of
properties)
the
writer
interest
of
Additional
to
FURTHER RESEARCH
suggestions
this
a nd
expensive
Well known
III more
many varied
work
the
to run
expensi ve
results.
modify
Some
both
more
Program modifications
and
5.3
of
be
useage and
proper
results.
several
of
Tests).
also
the
are
may be
number
UU
can
analyze
path
tests
(e.g.
It
such as
programs
for
experience
require
and
run,
path
(3)
proposed method.
when using the
effectiveness.
(2)
be aware of several
should
one
a practical matter
limitations
strain
such nonlinear stress
capability to model
this
have
does not
III however,
current version of BRACE
The
studies
applied
predicted vs
to
of
deformations ). Such
research
and
include:
the
actual
actual
further
for
type made
excavations,
performance
study
by
for
a
Cl ough
i. e.,
(e.g.
variety
of
soil
and
155
the
ted numerical
sophistica
broa den
hopefully
time
(2)
and
our understanding of
the
updating
Evaluation and
and
method
by comp arison
the
Nakaga wa
test s)
test
data
avai lable
data
and
can
the
of
modeling
th e
an
and
in
and
so il
BRACE
the
(Jaworski
is
el ements
node
wh ich
assum e
the
h ave
limited
the
III
not
updated.
interaction
program.
have
maintain
straight
only
tw o
soil
degrees
boundaries
in
There
between
soil
maintained along
the
and
three
test
program
one
the
two
continuum.
degrees
of
of
freedom
the
The
freedom
cur ve d deformed positions.
elements
position.
of
(i.e.
1973).
boundar ies between
dimensional
per
BRACE
computer
sh e e tin g elements
elements
test ing
prediction
dimensional
wall
results.
structure
c ompatab ility
inter-element
field
incompatability
sheeting e lements
this
From add itional
the
III
in
proposed
because of
to date.
s train
inherent
Displacement
role of
the
additional
are needed
r ev ised
be
predict ion
using
measur ements
field
Improvement
is
the
with actual
site,
oedometer
input
of
oth er predictions
paper,
For
(3)
technique,
of
excavation.
braced
in
the appl icability
help evaluate
conditions would
Soil
and
deformed
156
Develop Brace
(4)
III program capability
nonlinear stress
to model
strain behavior, perhaps by
employing a subroutine which uses a hyperbolic
(1963).
relationship as proposed by Kondner
5.4 CONCLUSIONS
The objective of this
thesis was
apply a method which includes the
This
thesis shows
that
effects of pore
deformation in
to predict
change with time
to formulate and
one can combine the
pressure
an excavation.
Stress Path
Method to
obtain soil parameters with the Finite Element
Method to
perform analysis in a way
effect of
time
includes
the
on deformation of a braced excavation.
approach is outlined in
Advantages
that
of
3 and applied
Chapter
the approach outlined
The
in Chapter 4.
in Chapter
3
are:
(1)
Complex nonlinear time analysis
(2)
The fundamentals of
by
the engineer as he
A few tests
avoided.
field problem are examined
selects his
input so
that he
the problem.
retains a feel for
(3)
the
is
can be used and
extrapolated
to cover
an entire geometry.
The proposed approach
application to
to
for
three
the
For
is
the example in
an iterative procedure.
Chapter 4 suggests
that
The
two
iterations give a reasonable solution, especially
overall deformations.
the example case consisting of
an excavation in a
157
the
clayey silt,
effect of
time
the excavation is significant
and
on deformations within
although not major.
the excavation appear to
inward wall movements within
increase
by approximately
10 to
Heave
20 percent with consolida-
tion.
Within the
the
and
the excavation at
bottom of
depth,
the negative excess
the
20
to 28 meters) of
20 meter excavation
pore pressures due to unloading
the positive excess pore pressures due to
the dissipation of
large negative excess pore pressure
resulting heave
this
pressures due
is minimized.
particular soil
the negative excess pore
are offset by the excess pore
to excavation
pressures generated by surficial dewatering.
of time
the effects
small
in this case.
of flow,
pressure
the dewatering
In other words, because of
for this case.
For
small net excess pore
in a relatively
results
This
shallow or
dewatering, substantially offset each other.
surficial
and
(depth of
top 8 meters
the effect
on predicted movement
Consequently,
are relatively
With other soils and other
of
time on deformations
conditions
could be con-
siderable.
In addition, for this
shows
that
particular case the example
the undrained heave is
the consolidation movements.
ving higher
factors of
contribution of
significant.
time
large when compared to
For other situations
safety against
invol-
bottom heave the
to total deformation will be more
158
Again, a practical advantage of
is
the proposed method
that such fundamental behavior can be observed and
quantified by the engineer during his analysis
field situation.
of
the
159
DRAIMAGpE
-
-
EC,
-
A:G7G
-
V T- o ^> Po-AG
-io A' - A-
ro
I
*4
8EQTCAL.
ClIRVE
) - ACTLA L BEHANJIOR.
Ci'J\ E (3) -
-
FrTS ALL
5TAGES
TDE~L-ZEEh ~SEWWIFO APPLLCABLE Mr PREDICMlON
er EXCAVATicb
OF
sTAGE
-
LSIN9,T+E
$AME
Motu.e.LU.S FoR- PREi'ou.5 EXCAVA~TON STAGES WLL
R ESLLLT 1 MJ AN O\JER-PREtkCTlON OF STR AiN.
SIW
C,
$A tE
S
CANIT MoO
5TAGES vJiLL RESLUT
.US
FoR.
>EEPER
It-)AM UJDER-PREIt 'C-nON
OF 5TRAIN MA-GllTUDE.
LINEAR VS.
NON LINEAR
STRESS/STRAIN
FIG 51
160
Asymptote = (a 1
-
u3)lt
1/b
1
E'
= 1/a
Ct
C4 -4
U.)
Hyperbolic Stress-Strain Curve
4
U
Trans formed Hyperbolic
Stres s-Strain Drve
b
-4
Axial Strain,
E
FRoim OSA/4/ /977
HYPERBOL IC
STRESS
STRAIN CURVES
FI G. 5.2
161
LIST OF SYMBOLS
a
Intercept
C
Cohesion
CAU
Anisotropically consolidated triaxial
sheared under undrained conditions
test
CRSC
Constant
test
CAES
Center
CIU
Isotropically
sheared under
c
Coefficient
v
of K
line
intercept
rate
of
of
ESP
Effective
stress
H
Height
cut
h
effective
consolidation
Engineering
stress
Study
consolidation
tangent
of
on
consolidated triaxial test
conditions of no drainage
Initial
e
strain
for Advanced
E.
h
based
modulus
path
Elevation head
Pressure head
p
h
t
Total
head
Hd
Length of
K
Active earth
K
At rest earth pressure
ground surface
OCR
Overconsolidation
P.I.
Plasticity
P 9 P
T
3X
4
path
pressure
coefficient
coefficient,
horizontal
ratio
index
____
S
Undrained
TSP
Total
TSP-u0
drainage
shear
stress
Total
strength
of
soil
path
stress
path minus
initial
pore
pressure
162
u
Pore pressure
u
Steady state pore pressure
ue
Excess pore pressure
uD
Excess pore pressure due to excavation unloading
uE
Excess pore pressure due to dewatering
UU
Unconsolidated undrained
wn
Water content, natural
wy
Liquid limit
w
Plastic limit
P
z
Depth
z
Depth
U
to water
triaxial
test
table
Consolidation ratio
z
U
Average degree
Slope of
the K
of consolidation
line
Unit weight
Total
YT
unit
weight
of
soil
Unit weight of water
Strain
E
Young's modulus
(Ty
Total vertical stress
(Y
'3 o r
Total horizontal stress
Octahedral stress
Vertical
a
Horizontal
y,
So,
effective stress
effective stress
Initial
total and effective stresses, vertical
Initial
total and
Friction angle,
stress
effective horizontal stresses
friction angle
based on effective
163
REFERENCES
K.J., Wilson, E.L.,
Element Analysis,
Bathe,
Bjerrum,
Bjerrum,
Clough,
and 0, Eide
L,
Excavations in
Numerical Mehtods in Finite
Prentice-Hall 1976
(1956).
Clay,"
"Stability
Geotechnique
of Strutted
1.
6, No.
"Earth
L., C.J. Clausen, and J.M. Duncan, (1972).
Pressures on Flexible Structures - A State-of-theArt Report," Proc. of the Fifth European Conference
on Soil Mechanics, Madrid, Vol 2, pp 169-196.
G.W., and Davidson, R.R., "Effects of Construction
on Geotechnical Performance", Dept. of Civil
Engineering, Technical Report No. CE-214, January
1977.
Clough,
G.W., Duncan, J.M., "Finite Element Analysis of
Retaining Wall Behavior", JSMFD, ASCE, Vo. 97,
December 1971.
Clough,
G.W.,
Clough,
G.W., and Schmidt, B, "Design and Performance of
Excavations and Tunnels in Soft Clay", Dept. of
Civil Engineering, Technical Report No. CE-235,
Clough,
G.W.,
Personal
Tsui,
Y.,
Communication 1980
"Performance
of
Tied
Back Walls
1977
in
Clay ", Paper presented at the National ASCE
Meet ing, Cincinnati, Ohio, April, 1974.
Cole,
K.W., Burland, J.B., "Observations of Retaining Wall
Movements Associated With a Large Excavation",
Proc. 5th European Conf. on Soil Mech.
Foundation Engineering,_Madrid 1972
Corbet,
and
"A Load Bearing
B.O., Davies, R.V., Langford, A.D .,
Diaphragm Wall at Kensington and Chelsea Town Hall
at London", Proc. Diaphragm Wall s and Anchorages,
Inst. of Civil Eng., London, 197 5.
"Effects of Foundation
D'Appolo nia, David J., (1971).
Construction on Nearby Structures," Pan American
Conference on Soil Mechanics and Foundations,
Puerto Rico, pp. 189-236.
Introduction to the Finite Element
Desai, C.S., Abel, J.F.,
Method, Van-Nostrand-Reinhold,
" Design Manual DM-7"
Department of the Navy (1971).
Navfac Naval Facilities Engineering Command,
Washington, D.C.
164
Davis, E.H., and Christian, J.T. (1971), "Bearing Capacity
of Anisotropic Cohesive Soil", ASCE, JSMFD, Vol.
97, Sm5,pp. 753-769.
J.M. and Chang, C-Y.,"Nonlinear Analysis
of Stress and Strain in Soils", JSMFD, ASCE,
No.- SM5, Vol. 96, 1970.
Duncan, J.M., and Chang, C-y., "Analysis of Soil Movement
Around a Deep Excavation", JSMFD, ASCE, No. SM5,
Sept. 1970.
Duncan,
"Earth Pressure
DiBiagio, E., and L. Bjerrum (1957).
Measurements in a Trench Excavated in Stiff Marine
Clay," Proc. 4th Int. Conf. on Soil Mech. and
Found. Eng., London, 2, pp. 196-202.
DiBiagio, E., Roti, J.A. "Earth Pressure Measurements on a
Braced Sherry Wall in Soft Clay, Proc._5th European
Conf. Soil Mech. Found. Eng., Madrid 1972
Henkel,
D.J., "Geotechnical Considerations of Lateral
Stresses", State-of-the-Art Paper, presented at the
Specialty Conference on Lateral Stresses in the
Ground and Design of Earth Retaining Structures,
ASCE, Cornell Univ. N.Y., June 22-24, 1970
Jaworski, Walter E., An Evaluation of the Performance of a
Braced Excavation, Phd Thesis, M.I.T., June 1973
Kondner, R.L.,(1963), "Hyperbolic Stress Strain Response
Cohesive Soils," JSMFD, ASCE,VOL.89, No. SMI.
Ladd,
C.C., (1973), "Estimating Settlements of Structures
Supported on Cohesive Soils", MIT Class Handout.
Ladd,
C.C.. (1971), "Strength Parameters and Stress Strain
Parameters of Saturated Clays", MIT Class Handout.
Ladd,
C.C. Wissa, A.E.Z. "Geology and Eng. Properties of
Conn. Valley varved Clays with Special Reference to
Embankment Construction", Dept. Civil Eng. Report
R-70-56
Lambe,
T.W., Wolfskill, L.A., and Wong, I.H., "Measured
Performance of Braced Excavation," Journal of Soil
Mechanics and Foundations Division, ASCE, Vol. 96,
May 1970, pp. 817-836.
Lambe,
T.W., and Whitman, Soil Mechanics,
New York, 1969.
Wiley & Sons,
165
T.W., "Interpretation of Field Data", paper from Proc.
of Lecture Series in Observational Methods in Soil
and Rock Engineering, University of Illinois, pp.
Lambe,
1970.
116-148, Dec.
Lambe,
T.W., "Predictions in Soil Engineering", 13th Rawkine
Lecture, Geotechnique 23, No. 2, 149-202. 1973.
Lambe,
"Braced Excavations," ASCE Conference
T.W., (1970).
on Lateral Stresses in the Ground and Design of
Earth-Retaining Structures, pp. 149-218.
Lambe,
"The Behavior of Foundations During
T.W. (1968).
Construction", JSMFD, ASCE Vol. 94, No. SM1, pp
93.
Vol.
93,
Lambe,
Lambe,
T.W.,
No.
"The
SM6,
T.W.,
Marr,
Stress Path
Proc. Paper
W.A.
"The
Method", JSMFD, ASCE,
5613, Nov. 1967.
Stress
Edition" JGED, ASCE, Vol.
June
M.I.T.,
Path
105,
Method,
No.
Second
GT6 pp.
727,
1979
Dept of Civil
Engineering,
"M.I.T. Test
Instrumentation MBTA Haymarket - North
Project" Mass -MTD-2, March 1972.
Mitchell, J.K.,
ment of
Section
Extension
and W.S. Gardner(1975), "In-Situ MeasureVolume Change Characteristics,6th PSC,
ASCE,pp. 379-391.
Peck,
Hansen,
and
Thornburn,
Foundation
Engineering
,
Wiley,
1974.
Osaimi,
A.E. and G.W. Clough (1979) "Pore-Pressure
Dissipation During Excavation, Proc. of ASCE,
Vol.
Osaimi,
105,
No. GT4,
A.E., "Finite Element Analysis of Time Dependent
Deformations and Pore Pressures in Excavations and
Embankments" Phd Thesis, Stanford University Dept.
of Civil Engineering
Palmer,
1977.
"Analytical Study of
J.H. Laverne, and Kenney, T.C.
a Braced Excavation in Weak Clay" Can. Geotechnical
Journal Vol.
Peck,
JGED
pp. 481-499.
9, No.
2 pp. 145-164
May 1972.
"Deep Excavations and Tunnelling in
Ralph B., (1969).
Soft Ground," State-of-the-Art Volume, Seventh
International Conference on Soil Mechanics and
Foundation Engineering, Mexico City, pp. 259-281.
166
Ries,
the
of
Carol, Predicting Lateral Earth Pressures for
Design of Tie-Back Retaining Walls',' Master
Science Thesis, M.T.T. 1974.
Skempton, A.W.
Slip:
"The Bradwell
and P. LaRochelle, (1965).
A Short Term Failure in London Clay"
Geotechnique, No.
Taylor,
15 pp.
222-242.
R.L. and Brown, C.B., "Darcy Flow Solutions With
Free Surface, "Journal of the Hydraulics D iv is ion
ASCE,
93,
Vol.
No.
HYZ, pp.
25-33,
Mechanics,
1967.
John Wiley
Terzaghi,
K., Theoretical Soil
Sons, New York 1942.
Terzaghi,
Soil Mechanics
K. and R.B. Peck (1967).
and Sons, New
Wiley
Practice,
Engineering
and
in
York.
Foundations, _ Retaining
Tschebotarioff, Gregory P., (1973).
Walls and Earth Structures, McGraw Hill, New York.
Wong,
I.H.,
Analysis
M.I.T. 1971
Zienkiewicz,
O.C.,
of
Braced
Cheung,
Excavations,
Y.K.,
The
Finite
Phd.
Thesis,
Element Method
in Structural and ContinuTm~Hicnics,~Ion~on,
McGraw-Hill Publishing Co., Ltd 1967.
167
APPENDIX A
GRAINSIZE
CONSOLIDATION
PLOTS AND
PLOTS
-
SQUARE ROOT
NAKAGAWA SOIL
OF
TIME
SPECIMENS
IN.
2
100
-
IIN.3/41N.1/2 N.
-
-
U.S. STANDARD SIEVE SIZE
NO.4
NQ20
NQIO
-
NQ 40 NQ.6
NO.OO NO. 200
-
90
-
----.-.-.-.-.-
---...-.-
so
.
-
.
_
-
-
_ __
-
_
-~-
I
___
-.--
-
-
-........._
--
-_
_
I -__TI
-_
-
-I-
-U T0
-
-
.--
60
-
-
- -
--
- -
z
-I
50
-
40
-
-
-
-
-I
--
-
-I
- - ---
E
.-
-
_
-
t0
0
10
100
1.0
SIZE IN
GRAIN
m{
-
_
20
4
G)C
m
-
-
-.
30
mmm>0
j --
--
>
CDBLESC
GRAVEL
0
COARSE
IE
UNIFIED
TEST
NO,
sYM
L-1
S-I
0
Tokyo,
0.001
SILT OR CLAY
MEDIUM
FINE
SOIL CLASSIFICATION
Japan
i
SYSTEM
MATERIAL SOURCE
SOURC
-
0.01
SAND
I
ICOARSE1
0.1
MILLIMETERS
REMARKS
I
lakaiaga.
Treatment Plant
I,te 13
. -.
F6. A-
IN. 3/41N.1/2
I l l---
2 IN.
100
-
90
U.S. STANDARD SIEVE SIZE
NO.4
NQ.20 RQ.4OfQ6ON.IOO NO.20
N .UO
-I
i
IN.
-
I
-
1
t~--
-
I---
so
T
--
T
r
-
-I
-I-
1
-T~
I
-
-
_
T -
-
I
TO
-
_-
-_
-
I
60
50
0
x
~
40
q
r
-4
I
_I-I
_
~
-
--
~
-I
----
---------
F~
-I
---
30
-
I-
-
_
-
20
I
O
10
XI -3
<0
_j(flW
--
m
0
-
100
10
GRAIN
1.0
SIZE IN
0.1
0.01
0.001
MILLIMETERS
90
SAND
GRAVEL
CDBLES
m
z
>0
SILT OR CLAY
FINE
COARSE
COARSE
UNIFIED
z
TEST
SYM. I
N-2
0
A
MEDIUM
FINE
SOIL CLASSIFICATION
SYSTEM
MATERIAL SOURCE
Tokyo,
Japan
REMARKS
I
I
Hakagawa
Troatment Plant
2ite B
FIG. A.Z
U.S. STANDARD SIEVE SIZE
I IN. 34IN.1/2 IN.
NO.4
NAI0
k.20
2 IN.
100
I
----90
---
so
Io
-
-
-
-
T
-
-
--
a-
-
-
T
-
_ _
-
-
-
-
T
a-a
--
T
rf
-
- -
0
NO.40 NO.60 NO.100 O.200
-- - -
-
I-
--
-
--
_-
60
so
-
-
-
mt
-
- --
- --
40
1
'
1
3D
g---
-
F'
z
--
-a
C
20
I
j
II
I
I
______-
10
ci
-X
(n CD
m
:4
I0
100
0.1
1.0
GRAIN SIZE IN
OBBLES
z ->
01X
0
CO
EA
UNIFIED
>
TEST
NO.
0-3
H-3
SYM.
___
MEDIUM
0
REMARKS
________
Japan
CLAY
SYSTEM
MATERIAL SOURCE
Tokyo,
OR
FINE
SOIL CLASSIFICATION
____________
A
SILT
SAND
GRAVEL
COARSE
COARS
0.001
0.01
MILLIMETERS
_
Hakagawa Treatment Plant
Site B
-
_
F/6. A.3
U.S. STANDARD SIEVE SIZE
4
Ni0 .N12I
O
IN .3'4!Nf/2
.N f./
1N .
100
90
----
N
-T-
- -T
0440 NO63NO.lOO
00N.0 m.
O 0O
O0
-
90
I
V
f"u
Al
1
i
--
-I
70
.1
60
so
--
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--- A
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--
50
-
40
-
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~
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30
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20
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--
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to
-
y
0
09LE -
C
0
SIZE IN
GRAIN
z0
C
GRAVEL
00LSCOARSE
FINE
COARSEI
UNIFIED
TEST
NO.
SYM.
-
11-4
A
Tokyo,
MILLIMETERS
SAND
SILT OR
MEDU
Japan
CLAY
FINE
SOIL CLASSIFICATION
MATERIAL SOURCE
0.001
0.01
0.1
.0
10
100
z 00
SYSTEM
REMARKS
1Jakarawa Treatment Plant
B
: itr
6/G. A.4
U.S. STANDARD SIEVE SIZE
NO.4
NQ.20
N .10
IN.3/4 IN.1/2
I2f IN.
t00
IN.
NQ40NO.60NO.100 ON.200
90
90
I
TO
-4
-
60
-
---
-
-
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TV1
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so
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30
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I
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-- acn w
rG
m
z
to
0
too
10
GRAIN
1.0
SIZE IN
0.1
0.001
0.01
MILLIMETERS
SAND
GRAVEL
x11
-3
-
-
--
-I
20
;u
I
40
--
-4
-
I-I
v"(i
UNIFIED
TEST
S-5
-5
SOIL CLASSIFICATION
SYM
MATERIAL
SOURCE
0
Tokyo,
Japan
A
SYSTEM
REMARKS
lakagrawa
Tratment Plant
:"I t f B
f16.A.s
IIN.3'4IN./2 N.
2IN.
U.S. STANDARD SIEVE SIZE
NO.4
Np20 NQ40NQ6ONO.IOONO.2O
NPO
I
ITII I
90
-
I
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30
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>
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n
0
10
t00
Z
GRAIN
in~I
>
GRAVEL
COARSE
TEST
P
SYM.
NO.
L-6s- 6
COARSE
MEDIUM
0.001
0.01
FINE
SOIL CLASSIFICATION
MATERIAL SOURCE
______________
0
0.1
SAND
FINE
UNIFIED
r -icn
1.0
SIZE IN MILLIMETERS
Tokyo,
A
Japan
SYSTEM
REMARKS
Hakagawa Treatment Plant
Site B
F /6. A.6
0
S
0
0
YE -
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40
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F16. A if
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182
APPENDIX
VERTICAL EFFECTIVE STRESS
B
VERSUS DEPTH
-
NAKAGAWA
183
0-
I0-L
uh
r 20-
i
LU
LU
307
LU
N
40+
500
10
20
40
30
TSM
NAKAGAWA
VERTICAL EFFECTIVE STRESS VS.
DEPTH
FIG.B.I