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CONSTRUCTION REMEDIATION AND MITIGATION
EA staff
has performed construction remediation and mitigation design for various
projects. Links to describe
our representative cases are presented below.
Click
Here to download
our Construction Remediation and Mitigation Project Sheet.
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RELATED LINKS:
EA provides management
consulting and technical services in four principal business areas:
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EXPANSIVE SOILS
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Subdivision-Wide Foundation Remediation, Erie, Colorado
Engineering Analytics
performed a forensic investigation and foundation remediation design for 80
single-family homes constructed at a site with highly expansive soils and
bedrock. The homes were constructed on 25-foot long piers with structural
basement floor systems, and experienced damage due to both free-field heave and
pier heave within five years after construction. A forensic investigation was
performed to identify areas of highly-expansive soils and bedrock, and to
determine the future performance of the structures without foundation
remediation and site re-grading. Site-specific geologic, geotechnical, and
hydrogeologic information was used to model subsurface water migration during
the 100-year design life of the residences. Anticipated free-field and pier
heave was calculated for each of the residences. Lot-specific remediation
recommendations were developed that included excavation of additional void space
under the foundation grade beams, foundation underpinning with micropiles,
excavation and replacement of expansive clay backfill, and lot-specific
re-grading.
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COLLAPSIBLE SOILS
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Site-Wide Remediation of Multi-Family Residential Complex, Basalt, Colorado
Engineering Analytics
staff completed a geotechnical investigation of six multi-family residential
buildings consisting of wood frame structures founded on post-tensioned
slabs-on-grade in western Colorado. Collapsible soils were identified at the
site in geohazard evaluations and pre-construction geotechnical investigations
during the 1990s. Within 10 years of construction, the buildings experienced
between 1.9 and 5.1 inches of differential settlement. Engineering Analytics
staff led the site-wide remediation design and construction oversight. The
project consisted of the following:
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Performance of a forensic investigation into the cause of distress to the
structures, including performing soil sampling and laboratory testing to
characterize the depth and geotechnical properties of the collapsible soils
underlying the site, characterizing the site geology, and reviewing existing
design and as-built construction documentation.
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Determination of the future performance of the structures without foundation
stabilization.
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Evaluation of different methods of foundation stabilization for the
post-tensioned foundation systems.
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Preliminary cost estimates for different foundation stabilization
alternatives, and discussing the advantages and disadvantages of each system
with the client.
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EA
staff led the design team which included structural engineering,
geotechnical engineering, and civil engineering. Complete design and
construction specifications were developed for foundation stabilization with
compaction grouting. Complete design and construction specifications were
developed for site-wide re-grading and drainage improvements, as well as
site-wide re-landscaping and irrigation improvements.
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Engineering oversight during compaction grouting, building re-leveling, and
grading and drainage earthwork.
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Completion of an as-built report summarizing the results of the
investigation, the scope of the repairs, and recommendations for on-going
site maintenance.
Forensic
Investigation and Development of Foundation Remediation Alternatives, Glenwood
Springs, Colorado
Engineering Analytics
staff completed a geotechnical investigation and provided recommendations for
remediation of a single-family home in Glenwood Springs. The home was
constructed on soils highly susceptible to hydrocollapse. Engineering Analytics
conducted a forensic investigation of the site to determine the cause of the
distress and to develop recommendations for foundation stabilization. The
project included the following:
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Performance of a complete forensic investigation into the cause of distress
to the structure, including an evaluation of local geology and geologic
hazards, review of existing design and as-built construction documentation,
subsurface exploration and characterization of soil conditions, and
laboratory testing to determine subsurface material properties.
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Analysis of the future performance of the structure without foundation
stabilization.
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Preparation of recommendations for improving site grading to reduce the
potential for wetting the site soils.
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Determination of foundation stabilization alternatives, including foundation
jacks, compaction grouting, and underpinning with micropiles.
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Development of preliminary cost estimates for different foundation
stabilization alternatives, and discussing the advantages and disadvantages
of each system with the client.
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Development of a preliminary design for the chosen stabilization method,
compaction grouting.
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Development of a risk analysis of future movement of the structure for
various depths of compaction grouting.
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Foundation Stabilization,
Basalt,
Colorado
Photo of Compaction Grouting,
Basalt,
Colorado |
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LANDSLIDE / SLOPE INSTABILITY
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Slope Failure Mitigation for an Open Pit Mine, Imperial County, California
Engineering Analytics is
performing ongoing geotechnical engineering and slope failure mitigation support
for an active open pit gold mine in Imperial County, California. The open pit
mine is currently over 500 feet deep, with an approximate length of 1,300 feet
of exposed pit crest that parallels a State Highway. The mine is located in a
seismically active area of southern California, and the pit walls are composed
of highly faulted and fractured overburden and bedrock that is considerably
prone to slope failures along the bedding and faulting planes. The gold mine has
a history of periodic pit slope failures which temporarily halt mining
activities and could impact the safety of the mine workers.
EA has performed ongoing engineering support to mitigate slope failure risks for
all the pit slopes on the property, with an emphasis on the slope that parallels
the state highway. As part of our mitigation design for the pit slopes EA has
developed geologic cross-sections, performed laboratory testing to determine
material strength parameters, performed static and pseudo-static anisotropic
slope stability analyses of the failed pit wall slopes, and provided pit design
alternatives to decrease the future potential for wall failure. These design
alternatives have included additional step-ins of the pit wall benching,
unloading of the pit crest, and buttressing. We have provided design
recommendations, stability analyses, and construction recommendations for a 2
million ton in-pit waste rock dump. The construction of this in-pit dump will
help buttress and increase the stability of a section of the pit wall that
parallels the highway which runs along the pit crests. To improve the long term
pit performance EA has also provided recommendations for the implementation of
water management alternatives to minimize the impact of surface water on the pit
wall stability.
We have provided guidance to the mine for observation and monitoring of wall
movement and pit crest movement. Movement monitoring involves continually
mapping tension-related features along the crest of the pit walls and
measurement of crack movement with extensiometers. We have also worked with the
mine personnel to design a real time slope movement monitoring system. This
system is designed to provide slope movement profiles with depth and will allow
us to better calculate the risks of slope movement at the pit crest on human
health and operations.
Third-Party Review of Retaining Wall Reconstruction, Snowmass Village, Colorado
Engineering Analytics
performed a third-party review of a rehabilitation design for a failing
retaining wall. The retaining wall was constructed during the 1970s on a
creep-prone shale unit in mountainous terrain. The timber crib wall was
originally constructed between an upper and lower row of three-story
multi-family residential structures. The timber crib wall was buckling and
stabilization of the site required reconstruction of the wall and surrounding
slope, as well as control of surface water and perched groundwater. Engineering
Analytics reviewed existing site data, including soil and bedrock properties,
as-built construction documentation, and engineering design details for the
proposed tie-back earth anchors and a mechanically-stabilized earth retaining
wall. EA provided conceptual analysis and recommendations for alternative
stabilization systems, as well as recommendations for monitoring of the hill
slope and adjacent buildings prior to and during construction. EA developed
geologic cross-sections to determine retaining wall bearing materials, as well
as options to mitigate anticipated settlement associated with construction
across differing geologic materials.
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Photo of Slope
Failure, Open Pit Mine,
Imperial County, California
Retaining Wall
Reconstruction,
Snowmass Village, Colorado
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EARTH DAMS
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Investigation and
Remediation of Existing Dams, Springer, New Mexico
Engineering Analytics
staff worked in conjunction with the New Mexico Office of the State Engineer (NMOSE)
to develop and perform a geotechnical site investigation to examine the
condition of two existing, earth fill, municipal water storage dams near the
town of Springer, New Mexico. The project included the following:
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Geotechnical sampling and laboratory testing of the dam construction
materials, and subsurface instrumentation of the earthen dam.
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• Water seepage and slope stability modeling of the dams using the GeoStudio
2007 software. Global seepage analyses were conducted to estimate the
location of the phreatic surface for use in geotechnical analyses of global
slope stability. Two-dimensional seepage was analyzed for steady-state and
long-term conditions.
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• Slope
stability modeling for each dam included static, pseudo-static, and static
rapid drawdown analyses upstream and downstream of the dam. The
pseudo-static approach was used to model slope stability under seismic
conditions.
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Water Storage Dam,
Springer, New Mexico
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Engineering Analytics, Inc.
1600 Specht Point Road, Suite 209
Fort Collins, Colorado 80525
Phone: (970) 488-3111
Fax: (970) 488-3112
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Engineering Analytics, Inc. All Rights Reserved. |
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