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By Ryan Nagle, Eric Lindquist, Rob Jameson, Kelli Mccurdy, Serena T. Jang, John Gouchon

This paper discusses the challenges associated with the design and construction of a deep basement in downtown San Jose, California for the 200 Park Avenue project. The aim is to present the critical design issues, how the challenges were addressed, details of the selected shoring design, and the performance of the shoring system during construction. The critical design issues that will be discussed related to retaining the deep excavation and constructing the basement include shallow groundwater, artesian pressures, settlement outside of the excavation, shoring earth pressures, and shoring wall movement. Subsequently, the paper will describe why a tied-back cutter soil mix (CSM) cutoff wall was selected as the shoring system and how it addressed the critical design issues. The design of the tied-back cutoff wall will also be discussed. Lastly, the performance of the tied-back cutoff wall during dewatering and excavation and how it compared to the design will be included. The performance was measured through a monitoring program, including survey data points and piezometers.

Oct 31, 2023

By John Turner, Joseph Hakim, Peter Faust, Benjamin Turner, Michael K. Muchard

An overview is presented of a unique axial bi-directional load test performed on a 3.0-m diameter (118inch) drilled shaft in January 2023 in Tucson, Arizona as part of a bridge replacement project. The shaft was excavated using crane-mounted grab tooling, resulting in a slightly curved base and corresponding uncertainty about the nominal base resistance relative to a conventional flat excavation base. The shaft was approximately 80 ft long and the load assembly was installed about 8 ft above the base. The load assembly location was selected to balance the estimated axial resistance above and below the jacks, as is customary. However, the presence of a 13-ft thick layer of strongly-cemented caliche with unexpectedly high compressive strength (2.8 to 5.1 ksi) produced higher than anticipated side resistance above the load assembly, resulting in a very stiff reaction against which significant load was transferred to the bottom segment. The maximum test load of approximately 9,000 kips resulted in just 1/8-inch upward displacement of the top segment and 5.0 inches of downward displacement of the bottom segment when the jacks reached their maximum stroke. Mobilized unit side resistances for the top segment ranged from about 2 to 9 ksf. Mobilized base resistance was on the order of 75 ksf. Since a primary objective of the load test was to confirm unit base resistance exceeding the AASHTO limit of 60 ksf for refusal blowcount sand, the test was deemed very successful and allows significant optimization of drilled shafts for the project. The test results also confirm that a curved base resulting from grab tooling can generate significant base resistance.

Oct 31, 2023

By Matthew Paquet, George Aristorenas, Philip Shull, Mike Senior

The Long Slip Canal is located in Hoboken, New Jersey. To reduce flood risk and raise the site for future rail facilities, New Jersey (NJ) Transit constructed an extension to the Combined Sewer Overflow (CSO) and backfilled the canal. A significant challenge of the site was the compressibility of the soft marine clay in the canal during backfilling and impacts to adjacent CSO structures and an existing king-pile wall due to lateral spread of the clay. To limit impacts to the aforementioned structures when backfilling, NJ Transit’s designer specified soil mix ground improvement to be designed by the contractor. The contractor elected to Value Engineer (VE) the ground improvement with a pile-supported concrete Load Transfer Platform (LTP) to be constructed in the wet. Since the VE design bounded structures designed by NJ Transit’s designer, emphasis was placed on the impact of the VE design on adjacent structures. This paper will cover the unique aspects of this VE design and construction, including: comparison of the 2D and 3D Finite Element analyses, use of concrete to function as a LTP for underwater construction, and construction challenges in soft marine clays.

Oct 31, 2023

By Gerhard Lang

Due to the worldwide population growth, the development of sustainable infrastructure and the exploration of renewable energies play a key role. The increasing need for complex building structures involve the development of innovative deep foundation technologies. Conventional methods like bore piles reach their technical and economic limits under certain conditions. As an alternative, new mechanized technologies, mainly coming from the tunnelling industry, have been developed to overcome challenging mixed ground conditions, high groundwater tables or economic limits in greater depths. For more than 20 years, the mechanized Shaft Sinking technology (VSM) has been in operation to build foundation and shaft structures all over the world, for tunnelling projects or for intelligent underground parking systems. More than 100 circular shafts have been built with reinforced concrete lining, mainly through difficult, groundwater bearing soil, in depths of up to 115 meters. The VSM is completely remote-controlled from the surface and covers a diameter range from 4.5 to 18 meters. Offshore foundations, especially in non-drivable ground conditions and medium water depths require drilled installation methods. The Offshore Foundation Drilling (OFD) technology, based on the concept of a full-face tunnelling machine, enables a rapid and economically drilled installation of offshore foundations in variable ground conditions and rock strengths. In 2022, drilling works for the subsea installation of 73 monopile foundations have been completed with OFD for the St. Nazaire wind farm in France. With a drilling diameter of 7.7 m, this OFD equipment is currently the largest offshore drilling rig. This paper will present the mechanized technologies of VSM and OFD with their application fields and benefits to the construction industry.

Oct 31, 2023

By Bengt Fellenius

Hunter and Davisson (1969) wrote a pioneering paper that brought the presence of residual force and its consequence for pile load-transfer to the attention of the profession. The paper presented observations at the 1963 Lock and Dam 4 project of the Corps of Engineers, where, for one of the first times, strain-gage instrumentation was used in static-loading tests. The tests combined results from compression (push) tests with those of subsequent tension (pull) tests and presented an innovative analysis linking the results of compression and tension tests to determine the true load-transfer of the pile. The analysis established that driven piles are left with locked-in force-distribution—residual force—and that this force affected the evaluation of records from an instrumented static loading test. While the concluding recommendation that static loading tests should combine push and pull tests and the piles should be instrumented in order for the true load-transfer mechanism be determined was not that often followed by the profession, the paper certainly established the importance of the residual force. This paper adds additional insight by reanalyzing the original test records in terms of effective stress, as opposed to stress-independent method of the old times, and of pile movement as opposed to "capacity".

Oct 31, 2023

By Karen Dawson, Patricia Bennett

Designers and constructors of King County’s $275M Georgetown Wet Weather Treatment Station located in Seattle, WA, overcame classical Puget Sound Lowland geotechnical challenges to provide treatment of 70 MGD of combined sewer overflows (CSOs), provide 1.2 MG of CSO storage, and convey the treated effluent 1,600 ft to a new outfall in the Lower Duwamish Waterway. The site is underlain by over 200 ft of very soft to dense deltaic deposits with moderately high compressibility, low strength, and is susceptible to seismically-induced liquefaction. The industrial history of the area made contamination a consideration for deep foundation selection and restrictions on construction methods. This paper describes some of the key aspects of the project, including a water-holding structure able to tolerate more-thancommonly-accepted settlement by utilizing a robust reinforced concrete slab and relatively short rigid inclusions combined with load distribution mat, settlement monitoring and water preloading prior to constructing grade-sensitive features. Case history information is presented for construction of a nominal 100 ft diameter, 92 ft deep secant pile intake pumping station/equalization basin which utilized a 32 ft thick tremie seal to reduce construction dewatering risks.

Oct 31, 2023

By Vijaya Rao Parigela, Jason Redgers, Bushra Khan

Ground Improvement was required for adoptable roads profile below the designated Rights of Way as part of infrastructure and streetscape works for an urban development project over an area of 500,000 m2 in the Emirate of Abu Dhabi in United Arab Emirates, UAE. The site is heterogenous with low-lying coastal profiles consisting of marine and wind-blown aeolian deposits followed by medium to stiff silty and clayey deposits and mudstone causing unacceptable settlements in the past to roads and associated structures. Exacting specifications from client and consultant included various requirements in terms of achieving bearing capacity, overall stiffness of ground, friction angle, relative density, and mitigation of any liquefaction risk for site based on local codes and standards. As such an extensive soil investigation campaign comprising of Cone Penetration Testing, CPTs carried out to ascertain individual CPT profile each representing an equivalent area of 2,000 Sq.m. Critical part was the site characterization which in this case, soil classification according to Robertson, 2012 was utilized. Thus, ground improvement scheme was prepared using High Energy Impact Compaction, HEIC (depth < 2.5m), Rapid Impact Compaction, RIC (depth < 4m) and Dynamic Compaction, DC (depth < 8m) as required to meet the compaction criteria in conjunction with the general contractor. Post compaction Cone Penetration Tests, CPTs and load tests were further evaluated to demonstrate performance. Overall works included predesign, execution and post testing and design verification to show compliance to specification in line with contract requirements.

Oct 31, 2023

By Christopher Stouffer, Stefanos Papadopulos, Siobhan O'Reilly-Shah, Pedro Espinosa

Treasure Island is located in the center of San Francisco Bay, between the active San Andreas and Hayward faults. Treasure Island was constructed in 1930s at the site of the Yerba Buena Shoals, a shallow-water area directly north of Yerba Buena Island, a natural island. It was constructed from sand fill dredged from the surrounding shoals, placed within perimeter rock dikes. The first phase of the Treasure Island redevelopment included (i) geotechnical ground improvement for 40 acres of land, 3,000 feet of shoreline, and a causeway that connects Treasure Island to Yerba Buena Island, (ii) construction of new infrastructure, (iii) preparation of building pads for mid-rise and high-rise buildings, and (iv) construction of a new transit hub with a ferry terminal, ferry pier, floats, and a breakwater A comprehensive geotechnical investigation was conducted to evaluate the ferry terminal site seismic and geotechnical hazards and provide foundation solutions for the near-shore and off-shore structures. The main geotechnical hazards include the presence of soft marine soils, strong seismic shaking, seismically induced soil liquefaction and lateral spreading, seismic shoreline instability, and kinematic loading on off-shore deep foundations. Deep foundations of the ferry pier, floats, and breakwater were designed to carry kinematic loads due to lateral spreading of the liquefiable offshore soil layers and for the effects of the soft marine deposits. In addition, the design of the ferry terminal at the shoreline included the evaluation of seismic stability of the ferry terminal abutment founded in an area that received deep soil mixing ground improvement. This paper details the geotechnical evaluations and mitigations for the various ferry terminal improvements.

Oct 31, 2023

By Cary E. Ronan, Tyler Toledo, Justin Ray

The Oyster Point development is located near the San Francisco Bay margins in South San Francisco, just north of the San Francisco International Airport. The eastern peninsula of Oyster Point was formerly operated as a municipal landfill from about 1956 until it stopped accepting waste in 1970. The Oyster Point Landfill is currently being redeveloped in phases, in cooperation with the City of South San Francisco, as a combination of public open space, life science campus (laboratory/research facilities, amenities buildings, parking garage), and a hotel. This paper focuses on Phases 1 and 2 of the life science campus development. The site conditions vary drastically across the site with a portion of the site underlain by shallow bedrock and a portion of the site underlain by up to 40 feet of municipal refuse over 50 feet of soft, compressible clay (Bay Mud) and up to 80 feet of alluvial deposits, with bedrock at a depth of about 150 feet. The varying subsurface conditions below the planned buildings led to a foundation system consisting of a combination of shallow and deep foundations. Deep foundations consist of driven steel HP-piles for Phase 1 and augered cast-in-place (ACIP) piles for Phase 2. Because of a steeply sloping site, over 20 feet of fill was placed in some areas to create a level building pad, resulting in over 5 feet of long-term estimated settlement. This paper will discuss the challenges and lessons learned during redevelopment of the Oyster Point Landfill. Specifically, we will discuss the design of piles and utilities to account for longterm settlement and corrosion, pile load test results, and interpretation of load test data. We will also compare and contrast the use of steel HP-piles and ACIP piles installed for building support through the landfill within Phases 1 and 2 of the development.

Oct 31, 2023

By Erich Steinlechner, Freddy Lopez, Guido Maier

Due to the high damage potential that a possible flood event has for the densely populated areas along the 26 km-long “International Stream” of the alpine Rhine, the discharge capacity needs to be expanded from the current 3100 m³/s (100-year flood) to 4300 m3/s (300-year flood), in line with the requirements of the Swiss-Austrian project RHESI – Flood Control for the Rhine Valley. In this context, the existing 255m-long Rhine Bridge connecting the Austrian towns of Fussach and Hard is no longer able to ensure the primary framework conditions for flood protection and needed to be replaced by a new structure. The new Rhine Bridge Fussach-Hard, a state-of-the-art steel composite bridge with a separated rope construction, was designed to meet the new requirements for flood protection as well as to satisfy the increasing volume of traffic. The extremely unfavorable subsoil conditions, consisting of shallow, very soft to soft plastic lacustrine clay deposits, required a deep foundation solution for the substructure (abutments and piers). Due to the high flood risk, the construction of the substructure could only be carried out during a period of low water discharge (winter), resulting in a very tight construction schedule (winter half-year 2020/2021). For the deep foundation of the substructure, several options were evaluated. Finally, a solution consisting of pile grillages, executed with ductile cast-iron driven piles (320 mm of diameter), was adopted for the project. The fast, safe and simple execution of the piles allowed for the successful erection of the substructure within the limited available time frame. The completion of this construction stage was critical for the further phases. After a construction time of only 28 months, the Rhine Bridge Fussach-Hard was officially opened for traffic on November 18, 2022. The following technical paper presents an overview of the adopted deep foundation solution, focusing mainly on the design and execution of the piled foundation. Furthermore, additional topics such as the sustainability of the adopted solution and possible optimization measures will be discussed.

Oct 31, 2023

By Chelsea Riddle, Chris Woods, P. Richard Scheller, Kenneth T. Kniss

Throughout the world, there are typical site issues/constraints that could be considered a regional issue, such as soft, silty soils in alluvially defined areas or organic soils found in former marshlands. In areas of variable topography, earthwork, retaining structures, and slope stability are paramount challenges. A case in point is the uncontrolled strip-mine turnover found in the coalfields of northeastern Pennsylvania where the propensity is for available sites to share critical problematic characteristics – massive grading challenges and the presence of uncontrolled mine fills from historic mining operations. At the site of a speculative warehouse distribution center in Olyphant, Pennsylvania, both of these typical issues were present, the latter of which was exacerbated by the higher-than-average fines content of the fill materials, making them more susceptible to changes in moisture content. To further complicate matters, the onset of site construction was set for late fall of 2021, following excessive levels of rainfall in the northeastern United States over the previous two to three months, which led to significant quantities of trapped water within the mine spoil material. This paper will provide a case study on the efforts undertaken to identify and address the issues outlined above, focusing on the several geotechnical construction techniques required in concert to stabilize the site. Specific discussion will focus on the dynamic compaction program implemented for fill stabilization throughout much of the site, the aggregate pier program that became part of the solution in sufficiently loose and saturated areas, and the implementation of a settlement monitoring program conducted following the placement of up to 29 ft (8.8 m) of structural fill to establish the proposed site grades following the ground improvement work.

Oct 31, 2023

By Omar Conte, Feng Lu, Roger A. Archabal

The Sole Mia development is located in an area of North Miami, Florida currently undergoing revitalization that started in 2015. The overall site sits atop 184 acres of a former municipal waste landfill that was closed about 43 years ago. Langan, as the geotechnical engineer of record, has been involved in the design and development of the roadways, an 8-acre “Crystal” Lagoon, two 18-story residential towers, two large mixed-used 6-story complexes and a 7-story hospital with associated parking garage. Currently, Langan is engaged in high-rise development parcels (30+ stories), that are beginning construction. The landfill material is typically about 20 to 25 ft thick and it needs to remain in place during development. Long-term instrumented pilot test programs were created and implemented by Langan to evaluate the effectiveness of deep dynamic compaction (DDC) and preloading in order to minimize/effectively eliminate the short and long-term settlement impacts of landfill on the proposed development. Ground improvement has included DDC and/or preloading for support of roadways, parking lots, major underground utilities and light ground features. Medium to high capacity augered cast-in-place (ACIP) pile foundation systems have been evaluated, tested and ultimately used for support of the buildings/towers, including ground floor slabs. Pile installation through landfill and negative skin friction on the piles had to be considered in design.

Oct 31, 2023

By Shaun Wulff, Kam Weng Ng, Nafis Bin Masud, Opeyemi Oluwatuyi

Pile foundations are often driven in intermediate geomaterials (IGMs) to attain higher resistances in order to meet the increasing load demand, satisfy Load and Resistance Factor Design (LRFD) specifications, improve design efficiency, and reduce construction challenges. IGMs are transitional geomaterials that possess a high natural variability. However, these geomaterials are not well defined and characterized in the design and construction of driven piles. This paper presents the recent development using over 150 load test data on steel piles to comprehensively address current challenges with pile foundations in IGMs. A methodology is presented to classify soft rocks and soil-based IGMs to reduce pile design and construction uncertainties. New static analysis methods are developed and validated to improve the estimation of shaft resistance and end bearing of piles in IGMs. New procedures to model pile driving in IGMs using the wave equation analysis program (WEAP) are proposed to improve the construction control efficiency. LRFD resistance factors are calibrated using probability-based methods to achieve a target design reliability. Finally, extensions to include inherent variability and geological uncertainties of IGMs using geostatistics are suggested to develop a geotechnical investigation plan and improve pile design reliability.

Oct 31, 2023

By Brendan Stepek, Mike Senior, Gary Brill

Norfolk Southern Railway (NS) has mainline rail passing through the foothills of the Blueridge Mountains of Central Virginia. The project site is a 70-foot-high cross valley embankment fill in close proximity to an adjacent stream. The embankment has a history of instability dating back to the 1960’s with both significant track and slope movement and numerous attempted repairs. NS elected to have a comprehensive geotechnical study of the embankment performed, install slope inclinometers to identify sliding planes, and ultimately stabilize the slope. The slope stabilization system included a two-tiered system. The primary and lower slope support consisted of a concrete cap beam with post-tensioned tieback anchors and compression micropiles socketed into sandstone. The secondary and upper slope system consisted of a concrete cap supported by an A-frame layout of tension and compression micropiles in soil. All elements of the stabilization system were designed to allow for construction while the track remained in service without impacting rail operations. This paper will discuss the geotechnical conditions of the site including brief overview of past stabilization attempts, the design of the slope stabilization elements, and a successful construction summary given limited access and close proximity to active rails.

Oct 31, 2023

By John Bryant

As engineers, we must understand all possible failure modes and design structures to avoid or safely accommodate them. For the safety of our communities, we must remember that quality foundation engineering is imperative. These case studies provide insight into the awareness we must have and the adjustments we must make to avoid catastrophic, dangerous, and costly failures.

Oct 31, 2023

By Martin Hudson, Lisheng Shao, Navid Plaseied, Adam Richardson

At a project site in San Diego, California, the hazards of liquefaction and seismically-induced settlement were present, in conjunction with relatively compressible soils that would require a low bearing value for use of spread footings. In addition, the site had variable conditions such that a portion of the site did not exhibit such hazards. Therefore, vibro-replacement stone column ground improvement was chosen to be performed such that the multiple hazards would be mitigated, allowing for use of spread footing foundations for a new building throughout the site. The post-improvement seismic performance of the soils beneath footings was calculated and served as the basis for seismic design for the vibro-stone columns. The post-improvement static performance of the soils beneath footings was evaluated using a modulus test in the field. The results of the modulus test confirmed the design assumptions regarding static settlement. The construction techniques are discussed herein, as are the testing and calculations used to justify the mitigated hazards and compliance with the design criteria.

Oct 31, 2023

By Ramin Motamed, Fahim Bhuiyan

Damage dealt with by some recent major earthquakes has raised concerns among the geotechnical engineering community to delve more into the area of soil liquefaction. As part of research funded by Pacific Earthquake Engineering Research (PEER), a large-scale shake table test on a laminar soil box was carried out at the University of California, San Diego, to investigate the effect of liquefaction-induced ground motion on a shallow foundation. In this study, a 2D numerical finite difference simulation of the baseline test was conducted in FLAC using the PM4Sand plasticity model. Some general behavior of sand layers during liquefaction including generation of excess pore water pressure, development of shear and volumetric strain, and their relative contribution to the total settlement were investigated. The model predicted the average final foundation and free-field settlements to be 21.94 cm (measured value 26.05 cm) and 12.36 cm in heave (measured heave value 1.57 cm) respectively. The shear strain appeared to govern the total settlement during seismic excitation compared to volumetric strain, during strong ground motion, while the latter became more apparent after the ground motion had subsided.

Oct 31, 2023

By Greg Stokkermans, Jim Hansen, Mary Kate Dempsey, Mark Reinders

The City of Toronto is reshaping and revitalizing its waterfront in the largest ongoing urban redevelopment project in North America. The redevelopment includes naturalizing the mouth of the Don River, which has become a source of flooding as the city has been built around it. Constructing a new river valley to alleviate this bottleneck involves multi-staged excavations up to 7 meters below Lake Ontario in permeable alluvial sands. In order to place a protective environmental barrier, these excavations need to be dewatered and require cantilevered earth retention over 6 meters high. This paper highlights the rapid design and construction of a 1.1-kilometer-long, up to 45-meter-deep secant pile cutoff wall that was constructed to support the first phase of excavation and dewatering of the new river valley. The paper discusses the geotechnical investigation and seepage analysis, selection of wall type, verticality criteria requirements, and construction challenges associated with the deep secant pile cutoff wall. Data collected during construction confirmed that the cutoff wall met critical design objectives and allowed for successful construction of the new river valley.

Oct 31, 2023

By Casey D. Shanahan, Dustin Walkenhorst

The Howard Frankland Bridge megaproject consists of a new, 3.2-mile (5.1 km) bridge extending I-275 across Tampa Bay. Two steel sheet pile and combi-wall bulkheads with a total wall length of over 11,000 ft (3350 m) were required to create the land for the new roadway and bridge approaches. A total of 1,287 permanent grouted soil anchors supports the bulkheads, which in some areas retain a 20-ft (6.1 m) tall MSE embankment. Anchors with lengths up to 200 ft (60.1 m) were installed, and project design loads necessitated anchors that varied from 3-strand to 8-strand. The soil conditions at the site were typically loose to dense sands underlain by a thin layer of clay over karstic limestone of variable hardness. Given the magnitude of the design loads, the larger anchors were designed to bond into limestone. Limestone variability along the bulkheads was observed. In some extreme cases, the top of the limestone elevation varied by nearly 100 ft (30.5 m), which created challenges for designing the length for anchors that were required to bond into limestone. Given the proximity to Tampa Bay, most of the work was performed from a barge. Waler systems were installed on the waterside of the sheet piles, so installation and welding work was limited to lower tide stages. The geotechnical contractor designed and installed the anchor and walers systems to fit within the proposed concrete cap. The objective of this paper is to discuss the significant design and installation challenges of the anchor and waler system for this high-profile project.

Oct 31, 2023

By Brian Wilson, Franz-Werner Gerressen, Johannes Reinisch

Specifications for traditional auger mixing methods have made use of the Blade Rotation Number (BRN) to establish acceptable levels of mixing. Cutter Soil Mixing (CSM) has no such established parameter. Previous research has proposed the adoption of an Energetic Mixing Index for CSM and has attempted to establish a basis for this utilizing results from a limited number of panels. This paper reviews the basis of this previous proposal and assesses the applicability of the proposed index utilizing a review of production data from a number of sites in proximity to Vancouver, British Columbia, Canada. Based on the outcome of the review, the paper proposes adoption of a new index for initial field quality control of CSM operations.

Oct 31, 2023