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By Vivian M. Troughton, Clifford J. Wren, Tony P. Suckling

"Secant pile walls are used for the construction of deep basement walls and earth retaining structures. Risk associated with secant pile walls is commonly perceived as being the safety of site personnel and the public during piling operations, or safety used in design. It is recognized that both of these are of paramount importance, but additional risks associated with the construction methods must also be considered to complete the risk management profile for any project. For the particular case of secant pile walls, if Clients take a ""back seat"" they may be unaware of the total risk package they are procuring. The authors argue that the piling contractor should be involved at the earliest stage giving input into the overall risk management process. Such early involvement within the professional team will maximise cost benefits to the Client and minimise the delays and cost increases sometimes associated with these works. A consistent methodology for identifying and then managing all the risks associated with secant pile walls is proposed. An example is used to demonstrate how this methodology should be employed. INTRODUCTIONThis paper discusses the value of a complete and integrated risk management process for structures with basements formed using a secant pile wall.The risk associated with any secant pile wall can be consicfered as comprising four components;1. Safety of people on site2. Safety of design or design methodology3. Construction risks4. Commercial risksAny risk management system needs to fully consider and integrate each of these four components to maximise the likelihood of a successful outcome for the basement.This paper concentrates on the construction risks for secant pile walls, as these are not often understood by the Client (in this paper the term ""Client"" also includes the main contractor, principal contractor, Engineer, Planning Supervisor, quantity surveyor and cost consultant)."

Jan 1, 2005

By Steven E. Darnell, William W. Haasz, Brandon T. Buschmeier, Frederic Masse

"Landfills often cover expansive areas in locations where large building facilities or infrastructure is in high in demand after the land has been reclaimed. Most landfills have soil or fill properties that vary widely over small distances; combined with the strict guidelines and restrictions for the removal and treatment of soil or material that is on site, these projects can be a major challenge for any prospective developer. In order to make landfills suitable for the construction of any project it is necessary to conduct a detailed evaluation of the subsurface conditions. Ground improvement techniques are among the most typical methods for making reclaimed landfills suitable for the construction of any major project. The paper will discuss the approach that was taken to support a proposed warehouse in Elizabeth, New Jersey using Controlled Modulus Columns Rigid Inclusions (CMC Rigid Inclusions), which are grouted, auger-displacement elements. Additionally, we will discuss the use of Dynamic Compaction (DC) that was performed in areas outside the proposed warehouse footprint. Through the combination of CMC rigid inclusions and DC, the general contractor’s project schedule was expedited, the costs to support the warehouse were economized, and the anticipated settlement of the parking lot areas was drastically reduced. Furthermore, the paper will outline the benefits of using CMC rigid inclusions and DC methods in order to minimize the impact of working with contaminated soils from a landfill.OVERVIEW OF THE ELIZABETH WAREHOUSE PROJECTOver the past several decades the foundations industry has seen an increase in demand for the support of developments on reclaimed landfills; particularly, on the east coast where many landfills were capped before the 1980’s and steady population growth and city expansion have caused high demand for this now highly desired real estate. Unfortunately, these landfills, often as large as twenty (20) or more acres present tough geotechnical and environmental challenges for Owners planning to develop or build structures of any size on the reclaimed land. Consequently, the options for building on reclaimed landfills can quickly become cost prohibitive.Site SpecificSelected by a developer for the location of a future warehouse, the 29 acres (114,424 sq-meters) project site is located in Elizabeth, New Jersey and demonstrates the complexities of designing over a once reclaimed landfill. The landfill was used for municipal solid waste (MSW) consisting of trash, wood, metal, glass, plastic, brick, concrete fragments, and other types of debris. This landfill was capped in the 1960’s, and developed in the 1970’s for a warehouse. The new project included the demolition of the existing warehouse and the development of the site to be repurposed for a new 481,650 sq-ft single-story warehouse, surrounded by paved parking and truck loading areas. Figure 1 below, shows an overview of the project site layout."

Jan 1, 2017

By John D. Nelson

Foundation underpinning is a common component of remediation schemes for distressed foundations on expansive soils. For many applications in expansive soil, micropiles have distinct advantages over other techniques. This paper will concentrate on the design and construction of micropiles in expansive soil. It discusses the nature of building distress and the relationship between foundation movement and soil heave. It presents methods for determining the factors that are required for the design of micropiles. Such factors include calculation of expected free-field heave, depth of soil wetting, and prediction of pier movement. A finite element program developed by the authors and others to determine pier heave and internal forces is presented. The input parameters that are required for pier analysis are discussed, and the nature of the output and the sensitivity of the results to the output are described. A case example illustrates the advantages of micropiles over other methods.

Aug 1, 2013

By Joel B. Dellaria, Justin R. Lewis

"No. 9 Walton is a new high-rise condominium building located in the Gold Coast area of Chicago. The adjacent building, Walton on the Park, featured 4 levels of below grade parking and utilized a secant pile wall with integral drilled shafts to support the exterior columns. The earth retention system (ERS) for No. 9 Walton also employed a secant pile wall in combination with drilled shafts. The excavation into the soft Chicago clays varied in depth from 9.75 m to 12.5 m (32 feet to 41 feet) below grade. The temporary excavation support used internal braces from the new secant piles to the existing foundation system of Walton on the Park to provide earth retention. Engineering teams for both projects worked together to design the bracing scheme and connections to ensure that the new excavation and internal bracing would not overstress any elements of the existing structure. Further complicating the project, immediately to the west of the project was a historic church founded on shallow spread footings which required underpinning to minimize movements.The project involved three different building owners, small values for acceptable wall movement, an extensive monitoring program and the challenges of merging two earth retention systems. The subsurface conditions at the site, the adjacent structures, the excavation, and the performance are described. A summary of the design methods and the expected movements of the ERS are discussed, and the performance monitoring system is described. Overall, the ERS performed better than expected with less than 1 inch of measured lateral wall movement during and after the excavation was completed. Measured performance of the ERS is compared to the predicted performance and to the performance requirements for the project.INTRODUCTIONNo. 9 Walton is a new high-rise condominium building in Chicago located in the Gold Coast. The building has 3 levels of below grade parking and 36 levels of living space above grade. Developers originally slated the project to be Phase 2 of the Walton on the Park development built in the mid 2000’s, using portions of the existing foundation system for development of the new structure. However, the housing market crash in 2007 prompted cancellation of Phase 2 of the Walton on the Park development. The property sat undeveloped until 2015 when design and construction for No. 9 Walton began under a new development and design team. The project team completed foundation excavation and below grade structures in 2016 with the first units of the building turned over to new homeowners in 2017.The structural design for No. 9 Walton consisted of reinforced concrete columns and slabs, supported laterally by a heavily reinforced concrete central core. Drilled shafts to rock supported the interior columns and core with the exterior columns and foundations integrally included in the earth retention system. The structure had a below-grade footprint of approximately 1,490 m2 (16,000 ft2). The general excavation extended 9.75 m to 12.5 m (32 feet to 41 feet) below street level with the deepest portions at the central building core mat foundation."

Jan 1, 2017

By Frank J. Purcell

“Down The Hole” (DTH) hammer drilling is often necessary to advance the casing during pile construction where the test bores have determined difficult drilling conditions with obstructions such as boulders, cobble and glacial till. The use of compressed air to operate DTH hammers in foundation drilling has been a contentious point in many regions of the world due to its potential to disturb the ground around the pile being constructed. There are many examples of damage to adjacent building foundations where compressed air exiting the pile being drilled disturbed the subsurface around the building’s existing piles. This paper looks at the use of compressed air in DTH hammer foundation drilling and the move towards controlling the exhausted air to avoid over drilling the pile, causing potential damage to nearby piles. Simulated models of air flow penetration into the soil of different configurations of drill bits are discussed to highlight design changes employed to better control the air during the drilling process. A case study of the construction of a water-tight pipe pile wall for a building’s underground parking structure is studied to demonstrate the potential of DTH hammer foundation drilling where the air is fully controlled.

Nov 1, 2022

By Shreya Vivek Hokam, Dr. A. I. Dhatrak, S. W. Thakare, Dr. Vivek S. Hokam

Construction in congested urban areas has necessitated tall and massive structures. In urban areas, it is common to construct underground structure nearby existing buildings. Selection of an appropriate support structure system to be implemented in the excavation in an urban area is heavily dependent upon the geotechnical conditions and safety of the surroundings and neighbouring structures. Urban Rail, popularly referred to as Metro Rail, has seen substantial growth in India in the recent years. More cities are experiencing the need for metro rail to meet their day-today mobility requirements. The metro structures involved deep excavation for foundations which induces the stresses and thereby alters the existing equilibrium and thus may affect stability of neighbouring structures considering safety point of view. Hence, design and execution of deep excavations become one of the important challenging tasks of any geotechnical engineer in the modern era. Further, it is important to control the ground movement in order to prevent the failure of excavations. This involves specialized foundation technologies, usage of sophisticated equipment and new methods in underground construction, safety and monitoring systems. In this paper the methodology used for protecting adjoining structures due to deep excavation for Nagpur Metro station is studied.

Sep 1, 2022

By Brian McGlynn

There are many factors that can result in a site characterization being limited. For example, a client may undervalue the importance of a good geotechnical report, or an owner may feel that it would take too much time to perform an appropriate investigation among other reasons. For this project, neither was the case. The challenge was that the construction sequence of work required wick drains to accelerate the settlement of soil that had yet to be placed, resulting in the need to create a wick drain bid package based on unknown settlement parameters. This wick drain project took place in Long Beach, California, at the Long Beach Middle Harbor Re- development. For much of the past decade, the Port of Long Beach undertook a $1.5 billion redevelopment of two outdated terminals to create the Long Beach Container Terminal (LBCT). To achieve this goal, the existing terminals were demolished and the slip that serviced one of the older terminals was designed to be infilled to create the new area that would allow for the LBCT to manage 3.3 million TEUS (a commonly used freight term meaning twenty-foot equivalent unit) of cargo each year. Ultimately, the construction of the LBCT would be performed under multiple contracts to allow the new terminal to begin operation in a phased approach. Menard performed the wick drain installation under two out of three contracts, and this case history focuses on the challenges anticipated and faced under the second of these awarded contracts.

May 1, 2023

By Emad Farouz, Francis A. Abreu

"This paper presents a case history of a successful construction-phase pile load test program that optimized the pile design in challenging ground conditions at the Great Neck Wastewater Treatment Plant in the Town of North Hempstead in Nassau County, New York. The improvements and expansion of the wastewater treatment plant included the construction of several new structures to comply with new stringent nitrogen discharge requirements and new design flow. The challenging ground conditions included up to 20-ft thick organic deposits with weight of hammer blow counts and up to 14 percent organic content and tidal ground water that was near the ground surface. The foundation design evaluated various deep foundation alternatives and selected driven closed-ended pipe piles then filled with concrete as the most suitable foundation. The selection process included considerations of cost, risk, vibrations, noise, and schedule. The contract documents utilized an innovative approach of performing an optimization load test program that was implemented during construction to optimize pile lengths and reduce potential vibration and construction schedule.This paper discusses the details of the successful load test program including static testing, dynamic testing, and the innovative contracting approach utilized to implement the construction phase load test program. It also discusses the successful development and implementation of driving criteria for production piles and construction challenges. The successful load test program resulted in savings of several hundred thousand dollars, optimized schedule, and lower environmental impacts.SITE AND PROJECT DESCRIPTIONThe Great Neck Water Pollution Control District (GNWPCD), located in the Town of North Hempstead in Nassau, New York, owns and operates a municipal wastewater treatment plant (WWTP) that discharges treated effluent through an outfall to Manhasset Bay, which is a tributary of the Long Island Sound. The site is located west of Manhasset Bay and is surrounded on three sides by local roads, and commercial, industrial, and recreational properties. The site has a gentle slope ranging from elevation +20 to +7 from west to east, respectively, based on the Nassau County Datum.To comply with new nitrogen discharge requirements and new design flows, the GNWPCD contracted CH2M HILL, Inc. and William F. Cosulich Associates as a Joint- Venture (JV) to design and provide services during construction of eight new advanced nitrogen removal facilities."

Jan 1, 2017

By David J. Puller

As part of the value engineering process on a major Design Build highway project, instrumented trial pile load tests were used to achieve savings in cost and time on the foundations for a major river crossing. Two trial piles were tested close to failure load at 25MN. Following the interpretation of the pile load test results which included the determination of the ultimate shaft and base capacity, the mobilisation of the shaft and base resistance with pile displacement, and correlations with vertical effective stress and SPT profile, a revised design methodology was proposed. A 25% enhancement on commonly assumed ultimate shaft friction in Chalk was adopted. In addition a significant reduction in the Factor of Safety on end-bearing capacity generally used was also implemented. The revised design resulted in a significant cost and time saving on the piling operation with the pile length reduced by up to 6m (approx. 20%) for the river piers.

Jan 1, 2002

By David S. Graham, Benjamin Turner, Paul J. Axtell

Seismic challenges were at the forefront of design for two parallel replacement bridge structures over the Arkansas River as part of the I-30 Crossing Project in Little Rock, Arkansas. Although not an area of the country typically associated with high seismicity, proximity to the New Madrid Fault Zone resulted in design ground motions sufficient to trigger liquefaction in alluvial channel and point bar deposits. A detailed post-award subsurface investigation program utilized CPT with complimentary borings to obtain samples for laboratory testing to assess the continuity of potentially liquefiable layers, from which we concluded that continuous zones of liquefaction across the extent of the north approach could lead to lateral spreading towards the river. An overview of the foundation and superstructure design to resist lateral spreading forces in accordance with the latest published design guidelines and research is presented. Other seismic aspects of the design are covered including timber pile ground improvement to mitigate liquefaction at the north approach embankment and foundation input motions that differ from code-based ground surface motions due to foundation stiffness, strength, and geometry. The project showcases an example of successful collaboration between geotechnical and structural designers with contractor input to address seismic challenges in the South Central US. Furthermore, the importance of considering kinematic demands on columns and other superstructure components – not just foundations – is highlighted.

Sep 8, 2021

By Venugopal B, M Kumaran, Thomas John, Vetriselvan A

The initial pile load tests are conducted to ensure the geotechnical capacity of the pile in a particular site condition. Normally kentledge method is adopted for the compression pile load tests. In this method the entire kentledge load is loaded above secondary beams which are supported by concrete blocks above the Natural Ground Level. So, it is important to ensure the SBC (for shear and settlement) of the natural ground. In one of our projects initially it was decided to go with kentledge system for initial compression load test on 56m long 1200mm diameter BCIS pile. The test load and total kentledge load were 2160t and 2700t, respectively. The soil strata mainly consisted of clay with low SPT N value and water table almost at ground level. It was suggested to replace top soil using Granular Sub-base (GSB) with good compaction in order to avoid excessive settlement of concrete blocks placed to support the kentledge weight. When the kentledge loading started, even before reaching 10% of total kentledge load, excessive settlement on the GSB layer was observed. This paper describes the problems faced during normal kentledge method and how it was overcome using the liner pile system for initial compression load tests in this particular site condition for higher test load.

Nov 1, 2022

By Bernard B. Vannoy, Howard W. Gault, Ramesh Bobba

"Treviicos-Soletanche Joint Venture (JV) and the US Army Corps of Engineers (USACE) have installed a 3800-foot long, 275-foot deep and minimum 2-foot wide secant pile barrier wall at Wolf Creek Dam in Jamestown, KY. This paper describes the methodology employed by the JV and USACE to evaluate the overlap, thickness, and position of the barrier wall. It addresses the contractual requirements, positional uncertainty, and evaluation procedures.These procedures evolved over the course of the project as various issues were identified and procedures developed to evaluate these issues. During the project, it became clear that the JV and USACE could ascertain that the wall thickness and overlap requirements could be met if the overlap based upon Koden data was at least 0.7’ in the left-right direction. For a small number of piles with overlaps between 0.5’ and 0.7’, the piles are contractually compliant yet contain a minor degree of uncertainty in the overlap. Initially, the USACE assumption was that the amount of uncertainty of verticality measurements would require more than a 1-foot measured overlap in the left-right direction to confirm an actual, contractual 6-inch overlap. With time and experience, the limit of measured overlap was reduced in accordance with greater understanding of the equipment capabilities and tolerances. Other lessons learned include the need for Quality Control/Assurance personnel to collect data at the same starting point for every pile.For every pile the JV and USACE compared analog and digital data to provide confidence that the correct digital data was used for overlap calculations. Perhaps the most important lesson learned was the importance of the JV and USACE working together and sharing all data. Overlap analysis was performed by the JV’s Barrier Wall Specialist and a small number of USACE personnel. This resulted in a high level of experience and expertise within a small group.IntroductionThe Treviicos-Soletanche Joint Venture (JV) and the US Army Corps of Engineers (USACE) have installed a 3800-foot long, 275-foot deep, and minimum 2-foot wide secant pile barrier wall at Wolf Creek Dam in Jamestown, KY. The wall was installed through a 6-foot wide Protective Concrete Embankment Wall (PCEW) which was installed two feet into rock. The PCEW protects the embankment from erosion of drilling fluids during subsequent operations. Below the PCEW the piles were installed to a specified elevation (staggered at 475’ and 473’ below the 748.2’ work platform). The Ordovician limestone and shale bedrock is flat lying with few vertical fractures. These conditions facilitate the advancement of pilot holes with very low deviations (with considerable credit to the JV’s drillers and steering engineers). The pilot holes were spaced on 31.5-inch and 35-inch spacing. Subsequent enlargement of the pilot holes to 50’ resulted in a continuous wall. This paper addresses the requirements and procedures to assure that the wall was as wide, deep and continuous as specified."

Jan 1, 2015

By Terzis D. PhD, Katterbach M.

While awareness around the environmental impact of existing grout materials and chemical binders is increasing rapidly, biotechnologies are growing traction as sustainable alternatives in groundwork operations. Herein we present the principles and application methods of bio-grouting. The term is used to describe a system which is based on soil, groundwater or marine enzymes which are able to catalyze the production of calcite replicating a natural phenomenon. The system’s end result are mineral crystalline bridges which act as binders to improve the geotechnical properties of soils. This paper presents a comprehensive description of bio-grouts, their underlaying mechanisms contributing to mineralization as well as environmental considerations. With their water-like rheology, bio-grouts have a wide application range and are minimally invasive, requiring only very limited injection pressures. The equipment is the same as that used in conventional cement grouting, and the reactant components are worldwide available or easily suppliable, which explains why bio-grouting has nowadays become a valuable and sustainable alternative towards efficient soil treatment. Recent developments in the last years have allowed to further increase the applicability and efficiency of bio-grouts to ultimately bridge the gap between research and practice. A case study is illustrated in this paper showing the successful implementation of bio-grout for the stabilization of weakly cemented sandstone to safeguard an adjacent road segment in Switzerland

May 1, 2022

By Eric Lindquist, John Compagnone, Gabriel Carvajal

"Condon-Johnson & Associates, Inc. (CJA) with the assistance of design consultant, Brierley Associates, designed and installed a water tight shoring system utilizing several ground improvement techniques jointly. Prior to the installation of the shoring system, a test program consisting of the installation and testing of 7 jet grout columns; 1 soil mix panel; 7 soil anchors and 3 tie downs was performed to verify design assumptions. State-of-the-art quality control measures were employed throughout the project.The shoring system consisted of:•,Deep Soil Mixing (DSM) wall utilizing triple axis tooling to install overlapping columns along the perimeter of the proposed excavation to a treatment depth of 54 feet.•,Installation of steel piles in DSM to provide rigidity to the wall.•,Installation of a jet grout bottom seal, installed from surface to a depth of 58 feet below existing grade.•,Installation of 153 soil anchors, 1-1/4” diameter and 47’-6” length, to tie the jet grout bottom seal to the native soil below to resist hydrostatic uplift, installed from existing grade to a depth of 91 feet.•,Installation of walers and pipe struts for internal bracing•,Installation and stressing of 117 tie downs, 1” diameter and 16 ft length, to tie the pump station mat slab to the jet grout bottom seal, installed from inside the excavated pit.Subsurface conditions at the site consist of uncontrolled fill materials to a depth of 20 feet comprised of sandy silt and clayey sand. The native soils underlying the fill generally consist of soft and compressible lean clay and silt with varying amounts of sands to a depth ranging from approximately 44 to 54 feet below ground surface, which in turn are underlain by dense to very dense silty sand. The groundwater elevation at the site is approximately 8 feet below ground surface.This paper covers the design aspects, construction, and quality control measures undertaken by the geotechnical contractor, with supporting figures.INTRODUCTIONThe owner, County Sanitation District No. 2 of Los Angeles County, designed upgrades to their existing Long Beach Main Pumping Plant Facility. The upgrades consist of a new pump station that includes a reinforced concrete below-grade wet well and dry well, a two-story operations building, two 78-inch diameter pipe inlets, two 42-inch diameter discharge pipelines connecting the existing manifold, two pipe junction structures, two insert-type junction structures, and electrical transformers. This paper focuses on the excavation shoring for the new pump station. The original shoring design concept for the pump station excavation illustrated on the contract plans consisted of pressed in sheet piles, a jet grouted bottom seal with soil anchors, 2 levels of internal bracing, and tie-down anchors to resist hydraulic uplift forces on the buried pump station."

Jan 1, 2017

By Richard E. Sylwester

Evaluating surface and subsurface conditions for marine foundations (bridges, causeways, terminals, etc.) is often done with a limited amount of data. Subsurface information for these projects is primarily acquired using traditional methods, such as boreholes, test pits or divers, which tend to be expensive and limited in the area of coverage. A number of geophysical methods, including precision bathymetry, sidescan sonar, and seismic reflection or subbottom profiling are extremely cost-effective and obtain significantly more data than can be acquired using traditional intrusive methods. These geophysical methods provide detailed surface images and continuous profiles of the subsurface stratigraphy. This information can be invaluable for selecting the best location for geotechnical boreholes and to map potential geohazards such as submarine slides and filled or open scour holes. Offshore investigations conducted for a proposed highway bridge (Knik Arm Bridge, Cook Inlet, AK), the retrofit of two existing bridge (Antioch and Dumbarton Bridges, CA) and a proposed cruise ship terminal (Ketchikan, AK) used a combination of geophysical methods to map water depth, detect and map debris on the seabed, map the thickness of unconsolidated sediment, determine the depth to bedrock and identify potential geohazards such as scour holes. The results of the geophysical investigations will be used to select locations for obtaining geotechnical borings, to extrapolate geologic information between existing or proposed boreholes, evaluate the potential depth of scour and design a pile support pier. Geotechnical engineers, offshore contractors and bridge designers are realizing the importance of the early use of offshore geophysics for (i) site characterization, (ii) to reduce the uncertainty of geotechnical conditions thus avoiding designs that may be overly conservative and thus more expensive and (iii) to assist in selecting locations for geotechnical borings.

Jan 1, 2013

By Renzo D. Verastegui, T. C. Michael Law, Sitotaw Y. Fantaye, Alfredas Daugiala

"When completed, 520 Park Avenue will amend the Manhattan skyline and be one of the most prestigious high rise towers in New York City. The 52-story condominium building is located on a 60 by 100 feet lot on East 60th Street between Park and Madison Avenues. The geographically complex site is bounded by two fragile 5-story masonry buildings on the east and west, a mid-rise building on the north, and a New York City subway tunnel on the south. To add to this complexity, the ambitious development required 70 to 80 feet of excavation, mostly below groundwater level in highly permeable rock, to accommodate four levels of cellars. The new building also cantilevers 24 feet over a five-story historic building on the east. The limited footprint of the building coupled with large compressive and tensile axial loads, considerable base shear and over-turning moments, and the required deep excavation, presented unique foundation challenges. This paper describes how the challenges were solved with an innovative combination of permanent secant pile walls and drilled shafts.INTRODUCTIONThe project site is located at 45 East 60th Street, on the block bounded by East 61st Street to the north, East 60th Street to the south, Park Avenue to the east, and Madison Avenue to the west. As shown in Fig. 1, the site is surrounded on three sides by buildings sensitive to differential settlement. In addition, a NYCT underground subway structure lies below East 60th Street approximately 13 feet south of the site. The base of the subway structure is approximately 42 feet below the street.The project consisted of constructing a 52-story tall building. A portion of the superstructure cantilevers 24 feet over an adjacent five-story historic building. The underground construction for the new building involved a four-level basement, extending about 60 feet below ground surface. The excavation subgrade is much deeper than both the subway structure and the adjacent shallowly-founded building foundations."

Jan 1, 2016

By Arpana P. Sabu, Themis Vaxevanis, Sissy Nikolaou, Guillermo Diaz-Fanas

Geo-failures from extreme events (landslides, wild fires, earthquakes, floods, etc.) have increased exponentially in recent years around the world and within the USA. When catastrophic failures occur, they usually involve hundreds of fatalities especially in cases of unexpected triggering events, such as large intensity earthquakes or heavy flash floods. Protective actions against identified potential geohazards can mitigate the associated risks and the future occurrences and prevent these occurrences from becoming disasters, targeting the essence of resilience in geotechnical engineering. Imaging and other virtual design and construction tools can be used to identify weaknesses that trigger geohazards and can, in combination with numerical simulations, guide decision making. In spatially distributed problems, 3D visualization and LiDAR-type of technologies are essential in providing geotechnical engineers a deeper understanding of precarious soil zones and support finding appropriate solutions. This paper will present the value of using virtual design and construction technologies though the case study of the Iztapalapa suburb of Mexico, about 20 km southeast of Mexico City. Iztapalapa was developed within irregular topography and has a long history of severe soil subsidence. Following the 2017 Puebla-Morelos earthquake, the town experienced large settlements resulting in extensive damage to the already frail buildings and unregulated infrastructure. The soil subsidence was visualized by mapping available historic and geotechnical data. The visualization helped to identify areas where additional investigations were needed. Additionally, this paper presents a case study of a series of landslides from the 2016 Mw7.8 Muisne Ecuador Earthquake, which demonstrates the advantages of using novel technologies to collect data and create cloud datasets from drones and digital photos to understand and evaluate geo-vulnerabilities in anticipation of an extreme event and during rapid reconnaissance to plan for long-term instrumentation, which can enhance geo-disaster prevention and overall community resilience. INTRODUCTION Iztapalapa is a southeastern borough of Mexico City (CDMX) located within the Mexico Basin (Figure 1). This borough is a densely populated area of CDMX with a total of 1.8 million inhabitants, and has a third of its population living in poverty (Gonzalez-Hernandez et al., 2015) with limited to no access to clean drinking water. Iztapalapa also suffers from high rates of crime, drug trafficking, sex trade and illegal buildings. As the population continues to grow, the already non-regulated and fatigued infrastructure is unable to meet the community needs, especially during and after natural hazard occurrences. The region of CDMX is one of the world’s most seismically active regions that is also exposed to other geo-hazards such as floods, volcanic eruptions, and continuous settlement due to water pumping that has reached 11 meters over the past 100 years (Nikolaou et al, 2019). While the soil subsidence alone has caused significant infrastructure damage in Iztapalapa and throughout the rest of the city, recent earthquakes have also contributed to those damages.

Jan 1, 2019

By Shawna Munn, Sarah Speir

Cedarvale Station is one of 25 new Eglinton Crosstown light rail transit (ECLRT) stations along Eglinton Avenue in Toronto. It is an interchange station with the existing Toronto Transit Com- mission (TTC) University subway line and is located at the intersection of two major thoroughfares. The new LRT tunnels run below the existing Yonge Spadina subway line and required total excavation depths of 20 m (65 ft) to facili- tate construction of the new station.

Jan 1, 2023

By Harry Schnabel, Mitchell L. Fong, Douglas R. Jenevein, Thomas S. Lee

"The Warm Springs Extension (WSX) is one of a series of projects that will eventually extend the Bay Area Rapid Transit System (BART) from Fremont to San Jose, California. A cut and cover tunnel was used for a portion of the extension that runs through Fremont Central Park to minimize the impacts that an at-grade railway would have on the Park. A cement deep soil mix (CDSM) wall was selected by the engineer as the preferred method of providing structural support and groundwater cut-off for a portion of the tunnel where it passes through an important aquifer and near Lake Elizabeth. In addition to the CDSM wall, a jet grout plug was constructed at the base of the tunnel to provide a complete groundwater cut-off.This paper will discuss the unique quality assurance and quality control measures taken for the soil mix wall and jet grout plug as well as the methods used to repair leaks and mitigate water seepage through the exposed wall and grout plug.PROJECT DESCRIPTIONThe Bay Area Rapid Transit (BART) Warm Springs Extension (WSX) project is located south of the existing Fremont BART station extending 8.9-km (5.4 miles) to Warm Springs District in Fremont, California. The WSX project has been divided into two contracts with different delivery methods. In order to minimize impacts to Fremont Central Park, a subway was selected at this portion of the alignment under a conventional design/bid/build contract.The Fremont Central Park Subway (FCPS) which begins on the south side of Walnut Ave and ends just north of Paseo Padre Parkway and is about 2.3-km (1.4 miles) long. Fig. 1 shows the entire WSX and the FCPS project. The FCPS contract consists of a cut-and-cover subway box, subway transition structures, ventilation structures and a section of which transverses Lake Elizabeth (a man-made lake). The geologic conditions consist of fill (sand, silt, clay and construction debris), Young Alluvium (clay and silt), Basin Deposits (clay, silt, and sand), and Older Alluvium (sand and gravel) as shown in Fig. 2.HYDROGEOLOGY OF THE PROJECT SITEThe FCPS is dominated by two geologic features - the Hayward Fault and the Above Hayward Fault (AHF) aquifer. The AHF aquifer provides a significant source and storage of water for the local water district. The underground subway will penetrate this aquifer and is up to 11m (36 ft) below the groundwater table. No groundwater was allowed to be pumped during construction of the subway box by Alameda County Water District (ACWD). To facilitate excavation for the subway box, temporary cut-off walls and a grout plug were designed to retain and resist high differential hydraulic pressure. The following section describes the selection of a deep soil mixing method for water cutoff. Design of the grout plug has been described in Lee, et al., 2011 and Fong and Lee, 2009, and is not the focus of this paper."

Jan 1, 2015

By Thang V. Nguyen, Lisheng Shao, Gary E. Taylor

"The Community Memorial Hospital of Ventura, California, proposed to build a new state-of-the-art Cancer Treatment Center with radiation shielding walls and roof. The loose silty soils at the site had the potential to liquefy during an earthquake, which would result in significant settlement under the heavy footing loads. Treatment options included various deep foundation alternatives, as well as several ground improvement methods. The choice of wet soil mixing minimized the disturbance to the adjacent hospital during construction and potential settlement. Wet soil mixing allowed the structure to be supported on a raft foundation, meeting the stringent building total and differential settlement criteria. The authors also performed unit cell 3-D finite element analyses to evaluate the behavior of the wet soil mixing system in seismic loading conditions. This paper highlights the ground improvement design, construction, QA/QC, and the research related to evaluating the effectiveness of soil mixing for liquefaction mitigation.INTRODUCTIONThe Ventura Community Memorial Hospital proposed the construction of a new Cancer Treatment Center to replace the existing structure, which was built in 1901. The hospital complex is located in a wellestablished residential neighborhood. The soil conditions at the site of the proposed structure required ground modification to support the very heavy radiation treatment section of the building and limit settlement. Originally, 90-foot-long precast piles were considered for foundation support. Based on supplemental Cone Penetration Tests (CPTs) performed, the deepest CPT did not encounter competent pile bearing strata at a depth exceeding 30.5 m (100 ft). This could result in failure of the piles under long-term conditions, especially if hydro-consolidation occurs. The more realistic pile penetration depth would have been 36.6 to 45.7 m (120 to 150 ft). In addition, the excessive noise in association with pile driving would have been unacceptable to the community, patients, and staff of the hospital, so an alternative ground improvement solution was required.The specialty geotechnical contractor recommended wet soil mixing, an economical solution of creating a soil-cement product known as soilcrete that would significantly reduce the construction related noise and provide a more complete deep foundation for the structure.SOIL CONDITIONS AND SETTLEMENT CONCERNSThe subsurface soils were interbedded (Fig. 1) consisting of loose to medium dense silty sands, and soft to medium stiff silty clays to a depth of 30.5 m (100 ft). Groundwater was encountered at depths of 9.1 m (30 ft) and historical high groundwater was at 8.5 m (28 ft) below the ground surface."

Jan 1, 2015