INTEGRATION OF CONSTRUCTION FIELD DATA
AND GEOTECHNICAL ANALYSES
Yun Y. Su1, Jose N. Oliveira Filho1, Liang Y. Liu2, and Youssef M.A. Hashash2
ABSTRACT
Urban excavation includes complex engineering issues such as construction methods, support
systems, base stability, ground deformations, groundwater control, and influence on adjacent
structures. Additionally, the expansion of urbanization over the years has been generating an
increasing demand for underground space. Open cuts and tunnels have long been used to
create such urban underground space, but as the demand for underground space grows, those
excavation issues become even greater concerns. One of the greatest concerns when
constructing underground space, beyond conducting it in a timely and cost effective manner
while maintaining a safe environment onsite, is the impact of ground movements related to
construction activities. This paper presents the preliminary results of a research project which
utilizes 3D laser scanning technology to provide accurate 3D as-built construction data for
geotechnical analyses. Funded by NSF, this project explores the integration of construction
field data into geotechnical monitoring and forecasting that may potentially reduce the
impacts of urban deep excavations. The accurate 3D geometry data and construction
sequences provide new possibilities for geotechnical analyses at a higher precision.
KEY WORDS
3D laser scanning, excavation, field data collection, geotechnical analyses
INTRODUCTION
Urban construction excavations affect the lives of millions of people daily. To minimize the
impact on nearby structures, geotechnical and construction engineers must work closely with
contractors to design and monitor ground movements. Traditionally, engineers can estimate
ground movements using a combination of semi-empirical methods based in part on past
performance data and results of model simulation using finite element analyses. However,
predictions from model simulations contain uncertainties related to soil properties, support
system details and construction procedures. Given these uncertainties, it is common for urban
construction sites to install monitoring systems which record ground movements during
construction and, in some cases, movements of adjacent buildings. Significant developments
1
2
Graduate Research Assistants, Department of Civil and Environmental Engineering, University of Illinois at
Urbana-Champaign, 205 N. Mathews Ave., Urbana, IL 61801, Phone 217/333-7268, yunyisu@uiuc.edu,
foliveir@uiuc.edu
Associate Professors, Department of Civil and Environmental Engineering, University of Illinois at UrbanaChampaign, 205 N. Mathews Ave., Urbana, IL 61801, Phone 217/333-6951, 217/333-6986, lliu1@uiuc.edu,
hashash@uiuc.edu
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have been made in monitoring systems; examples are automated and wireless systems for
measuring lateral deformations using in-place inclinometers and building deformations using
automated total stations. This information is useful for geotechnical engineers if it can be
matched accurately with construction sequences and activities. However, engineers and
contractors continue to rely on limited records of construction activities field information that
are typically collected by hand. There is an obvious mismatch between the quality of data
from automated instruments and the record of construction activity.
This paper is organized into four main sections. The first section describes how
geotechnical engineers utilize construction field data to design and predict ground
movements in urban excavations. Following is a section that describes 3D laser scanning
technology. The third section reports results from a field study in the Chicago area
demonstrating how accurate construction field data can be used to benefit geotechnical
analyses. With better construction field data, geotechnical engineers can better predict the
ground movements due to construction activities and help contractors minimize their
impacts. Furthermore, using 3D laser scanning, contractors can better monitor construction
progress such as pay items, quality controls, and as-built dimensions. The last section
presents lessons learned from the study and provides a discussion for future vision on
construction field data collection and engineering integration.
IMPORTANCE OF ACCURATE
GEOTECHNICAL ANALYSES
IN-SITU
CONSTRUCTION
DATA
IN
Geotechnical engineers rely on in-situ construction data to update and predict ground
movements for urban excavations. Using numerical modeling and simulation, geotechnical
engineers can analyze and predict static and dynamic soil-structure interaction problems,
such as embankment loading, deep excavation, and tunnels. These analyses rely on field
measurements of as-built construction sequence, excavation volume, depths, case histories,
and soil behaviors. These field measurements provide input to geotechnical analyses that
utilize neural network (NN) and finite element analysis (FEM) to understand the dynamics of
stress strain, and movement. As an example, Figure 1 depicts a process of using field data to
train and predict ground movements during urban supported excavation using the so-called
“Autoprogressive” method (Hashash et al. 2003).
The importance of accuracy of field measurements cannot be over emphasized. Without
accurate field data, many predictive models will fail and, as a result, costly rework, repair,
and redesign may be needed. In reality, however, collecting accurate field data during
construction has not been easy. Equipment movement, personnel training, weather
conditions, site characteristics, and other interferences all contribute to the difficulties of
collecting quality field data.
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1. Field Measurements
Autoprogressive training of Neural Network based Constitutive
Model within the Finite Element method
Initialize: Train NANN using elastic training data and other
known material response from laboratory tests
Direct field calibration of the NN constitutive model using an
Autoprogressive training loop
2. Autoprogressive Training FEM
a) Simulate Construction
Sequence
=> extract stresses
At a given excavation/loading step
Step a: FEM- Apply construction history (force boundary
conditions) => Extract stresses
Step b: FEM-Apply measured displacements (displacement
boundary condition) => Extract strains
Step c: -New Training data: stress-strain pairs from Steps a & b
-Train NANN model using new training data
GOTO Step a
3.Forward FEM analysis with
trained NN material model
Stress-Strain Pairs
Training of NANN
b) Apply Measurements
=> extract strains
Neural Network
Constitutive Soil Model
at material points
New excavation stage
Figure 1 SelfSim framework using autoprogressive algorithm
Figure 1: Geotechnical Analyses Using Field Data (Hashash et al. 2003)
BACKGROUND AND EXISTING RESEARCH
Various researchers have explored construction data to benefit engineering decision and
management. Liu (1997) developed digital hard-hat systems for construction documentation
and collaboration. Garrett (1998) designed Mobile Inspection Assistant (MIA), a wearable
computer, for bridge inspection applications. Jaselskis (2000) utilized Radio Frequency
Identification (RFID) to track and collect data for construction materials. Beliveau (1991)
developed and commercialized a real-time positioning system for collecting 3D coordinates
in the field. Akinci (2002) investigated the integration of field data for automated assessment
of as-built conditions. These endeavors have led to new processes and technologies in
collecting quality field data. With the advances in information technologies, many new
sensors and sensing equipment are becoming available. The following sections will highlight
3D laser scanning technology and its application to support geotechnical analyses.
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3D LASER SCANNING TECHNOLOGY
Three-dimensional laser scanning is a relatively new technology that utilizes LIDAR (Light
Detection and Ranging). It is similar to RADAR (Radio Detection and Ranging), but uses
light to measure range or distance. A laser scanner consists of an emitting diode that
produces a light source at a specific frequency. A mirror directs the laser beam (with a
diameter of 6mm) horizontally and vertically towards the target. The surface of the target
then reflects the laser beam. Using the principles of pulse time of flight, the distance can be
determined by the transit time. The result of a scan produces point clouds, which can be
processed into accurate 3D models with the precision up to 6 to 8 mm (¼ to 1/3 of an inch).
LIDAR allows measurement of a large number of points in a relatively short amount of time;
these points allow engineers to analyze the excavation geometry in three dimensions. Figure
2 shows a scanner, Cyrax 2500 by Leica Geosystems Inc, and a schematic of the scanning
process. Each scan covers a 40x40 degree angle and is capable of collecting 1 million points
of data.
Figure 2: 3D Laser Scanner and Scanning Process
INTEGRATION OF CONSTRUCTION FIELD DATA AND GEOTECHNICAL
ANALYSES
With 3D laser scanning technology, geotechnical engineers can work with more accurate
data to perform analyses. It is a common practice for urban excavation sites to include a
monitoring program during construction to record the ground movements and, in some cases,
adjacent building movements. These observations can be used to evaluate how well the
actual construction process is proceeding in relation to the predicted movements. Ideally,
these observations can also be used to control the construction process and update predictions
of movements given the measured deformations at early stages of construction. The weakest
link, however, lies in the difficulties in collecting accurate construction as-built data in terms
of construction sequence, excavation profiles, and ground support systems. Using an
excavation project in the Chicago area, we field tested the accuracy and feasibility of
utilizing 3D laser scanning to collect more accurate construction as-built data for excavation
projects. Figure 3 shows a side-by-side comparison of site digital photo and a scanned 3D
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image. With the scanned image, actual dimensions can be obtained. As shown in Figure 4,
excavation profiles and measurements and terrain models can be constructed and analyzed
using finite element analysis software as stated in earlier sections. This integration allows the
geotechnical engineers to better understand and predict ground movements near the
construction sites thereby minimizing the potential impact, delay, and costs of urban
excavation projects. The research team is encouraged by the preliminary results and the
promise of 3D laser scanning.
Figure 3: Site Photo vs. 3D Scanned Images
17.7ft=5.4 m
23.4 ft=7.1 m
Figure 4: Excavation Profile and Dimension Measurements
LESSONS LEARNED
Several valuable lessons were learned from the research as we push the technology usage in
both construction and geotechnical areas. The following summarizes strengths, weaknesses
and opportunities of applying 3D laser scanning to both construction and geotechnical fields.
STRENGTHS
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


Accurate (approximately 8-19mm recorded precision on average) collection of 3D asbuilt dimensions of site and as-built component measurements
Safer and faster collection process as compared to traditional surveying methods
Data export to other A/E/C systems, such as CAD and visualization software
WEAKNESSES




Overlapping scans and target selection in progressive scans to combined multiple
40x40 degree scans into an integrated 3D model
Merging of coordinate systems and precisions from scans at different stages of
excavation
High cost of equipment and software
Training needed to become proficient in data manipulation
OPPORTUNITIES




3D Model generation and integration with other GIS (geographic information system)
Accurate as-built data for progress payment in construction claims and disputes
Automated and remote data capture via the Internet
Integration with technologies such as wireless communication and GPS (global
position systems)
RESEARCH VISION IN CONSTRUCTION FIELD DATA COLLECTION AND
AUTOMATION
Building upon our preliminary research results, we envision our future research endeavors
will lead to the following two results.
(1) AN INTEGRATED MODEL FOR EXCAVATION CONTROLS AND PREDICTION
From the lessons learned from our field tests, we believe the technologies, despite some
weaknesses, will enable engineers and contractors to work closely together to not only
enhance the quality of constructed facilities but also minimize the impact on neighboring
structures. Figure 5 shows a new approach to integrating field data into engineering analyses
and prediction. We envision the engineering and design objectives, such as costs and impact
on existing facilities, will be better served by having better models to predict ground
deformations. This prediction will be enhanced by accurate data from construction activities.
Instead of analyzing the model with only limited records of construction sequence and asbuilt data, detailed records will give engineers new ways to verify their models and better
predict the impact of construction activities. We also envision field data collection becoming
more automatic and less dependent on manual process by using sensors, sensing devices, and
wireless communications. We plan to develop an integrated GIS database to support 3D
virtual reality (VR) visualization and simulation. This new paradigm will change the current
ad-hoc update of field data into an intelligent and fully integrated environment for predicting
and controlling of ground movements.
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Engineering Design Objectives:
-economic underground space,
-minimum impact on existing facilities
Update simulation model of
future ground deformations
Now: ad hoc, nonNew: Intelligent update
Simulation model of anticipated
ground deformation
Adjustment of
engineering design &
construction activities
to control deformations
Data storage & use
Now: simple graphical
display.
New: 3D (VR), GIS display
Engineering design
Construction activities
Now: limited records
New: detailed records
Field data collection
Now: manual
New: sensors, wireless tech.
Figure 5: Vision of a Fully Integrated Model for Field Monitoring and Control
(2) CONSTRUCTION AUTOMATION IN INSPECTION, REPAIR AND PAY ITEM VERIFICATION
We also envision that sensors and sensing technologies will continue to influence how
construction field data are collected. Several promising areas that we are working on include
automatic dimensioning and inspections, repair analyses, and automated pay item
verification. Figure 6 shows a scanned wall segment (right) for automatic inspections of
dimensions and rebar spacing. A damaged column (left) was scanned for fractures and
damages assessment before repair. We are also exploring automated construction cost
controls, such as automatic pay item verification.
Figure 6: Scanned Components for Construction Inspection, Repair, and Pay Item (Courtesy
Network for Earthquake Engineering Simulation (NEES) at the University of Illinois at
Urbana-Champaign)
CONCLUSIONS
Urban excavations often affect safety and quality of the life of many citizens. Controlling
ground movements during urban excavation is key to ensuring the safety of neighboring
structures. The research presented in the paper shows the promise of using 3D laser scanning
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technology in monitoring urban supported excavation. Using 3D laser scanning technology,
geotechnical engineers and construction managers can improve the field data collection
process and the quality of collected data. Accurate records of construction staging in deep
excavations are critical in understanding and predicting the behavior of field excavation as
well as impacts on nearby facilities. The potential of the 3D laser scanning technology will
be further realized through the integration of the collected data into engineering analysis
processes. 3D laser scanning can provide timely and accurate as-built construction data
during excavation. At different stages of excavation, accurate terrain models derived from 3D
laser scanning can be automatically imported into a numerical simulation environment to
improve the accuracy of prediction on ground movements and deformations. This integration
of accurate field data with analytical models will help improve the quality of both
engineering design and construction. Despite some barriers, both technical and non-technical,
the future for 3D laser scanning technology is more than certain to become an integral part of
engineering analyses for urban excavation projects.
ACKNOWLEDGMENTS
This material is based upon work supported by the National Science Foundation under Grant
No. CMS 02-19123 under program director Dr. R. Fragaszy. Any opinions, findings, and
conclusions or recommendations expressed in this material are those of the authors and do
not necessarily reflect the views of the National Science Foundation. The authors would also
like to acknowledge our research collaborator Dr. Richard Finno and his research group in
providing access to the excavation site for conducting the field tests.
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