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By Luca Pingue, Regine Jagow-Klaff, Franco Muratore, Carlandrea Albonico, Damiano Frontini, Rudolf Wernecké

This paper describes an artificial ground freezing (AGF) application carried out to ensure both watertightness and structural support for the safe excavation of four cross passages of the Forrestfield Airport Link (FAL) project in Perth. The line will deliver 8.5 km extension of the existing urban rail network connecting the growing eastern suburbs of Perth with the existing suburban rail network. The proposed soil improvement technique is adopted as a smart alternative to jet grouting from the surface since the use of heavy equipment with long vertical mast was not allowed due to the line underpassing an airport in operation. In this paper, details of the challenges and lessons learned during both design and construction phases are given. Furthermore, it is described the geometry and the installation of freeze pipes in presence of a massive steel frame, ventilation system and slurry pipes of the tunnel boring machine (TBM) in operation. It is also illustrated the web monitoring system to allow key personnel to follow in real time the development of soil temperatures, tunnel convergences and ground surface deformations as well as changes in the interaction between international parties involved due to the COVID-19 pandemic.

May 1, 2022

By Davide Grassi, Joel Joaquin Cortez, Giovanni Spagnoli, Nick Chittenden

Grouting is a technique used to improve the engineering properties of soils and rocks. Grouting techniques are classified under different criteria: injection method used, type of grout material injected, typical application, and the sequence of construction. The best-known criterion is the mode of entrance or admission of grout into the soil or rock. It is possible to identify therefore several grouting techniques: compaction, fracture, jet/mixing and permeation. The function of penetration grouting is to reduce the permeability of the soil or rock and/or increase the strength and density. In order to avoid displacement, permeation grouting shall be carried out at carefully controlled pressures and flow rates, using appropriate grouts. Colloidal silica is an innovative binder which has low viscosity (about 5 m·Pas), it is not toxic (pH lower than 9) and it is workable between +5°C and +45°C. This paper presents several case histories: a consolidation job related to the installation of a new sewer in North Italy in cohesionless soils, water stopping injection in a weathered granitic bedrock in California, permeation works in the US in sandy soils to improve excavation and the installation of sheet piles in the UAE. Results show that the colloidal silica an innovative and robust technology to perform grouting in very fine soils where conventional binders or micro-fine cements cannot penetrate.

May 1, 2022

By Ian Vaz, Takefumi Takuma, Rafael Holcombe, Chris DellAringa

"This paper will discuss the successful installation of seawalls for the first phase of a project in Long Beach in California known as the Naples Island Permanent Seawall Repair – Phase 1. How an unconventional method of pile driving resulted in the reduction of the duration of the project while using less space and maintaining minimal noise impacts to accommodate neighbors will also be discussed. Included in the paper will be how non-vibratory equipment used on this project also significantly minimized the risk of disturbances as well as settlement on residential properties; which in turn greatly reduced the risk of damage to existing structures. The first phase of a 6-phase project along a section of the canals with tight clearances and proximity to residents included the installation of a 1,912 linear-foot steel sheet pile wall system in front of the existing deteriorating walls from January until March 2015.INTRODUCTIONThis project was located in the Naples Island neighborhood of Long Beach in southern Los Angeles County, California. After 80 years of the same seawall structures lining the canals of this beautiful neighborhood, the City of Long Beach Department of Public Works decided that it was time to better protect the area’s multi-million dollar homes by repairing its crumbling seawalls. The City realized that the walls will only become worse due in part to several concerns, including bending failure for the already deflecting walls. According to the City, certain sections of the walls had a significant risk of global failure if the area experienced a “moderate” near-source earthquake (City of Long Beach, CA, 2014b). Although the seawalls were in need of major repair, this would not be simple. Due to the tight clearances of the seawalls between the homes and canals, installation would be difficult with heavy, conventional construction equipment.Phase 1 of the project involved installing sheet piles on the water side in front of existing and aging vertical concrete seawalls between the Ravenna and Toledo Bridges along the Rivo Alto Canal. See Figure 1 for the General Plan for Phase 1. Financing for this project by the City’s Tidelands Capital Improvement’s Division allowed the construction to begin in a timely manner. However, the challenges for the City included regulatory restraints that further complicated the construction in terms of the duration of the project due in part to numerous regulations from several regulatory agencies."

Jan 1, 2016

By Julie Clarke

In 1939 Dr. Ralph Peck criticized the Civil Engineering community for taking a bifurcated approach to the prediction of building damage due to subsurface geo-technical works. Specifically, he observed that Geotechnical Engineers concerned themselves only with subsurface issues implying that their results were largely independent of the presence and condition of the structures above. He continued that Structural Engineers charged with risk assessment of buildings approached their work nearly in isolation of below ground activities. Seventy years later, although the state-of-the-art has enabled a better understanding of soil-structure interaction, the reality remains that risk assessment from subsurface construction, is not yet an integrated activity when done on a large-scale basis. To help move beyond this, this paper proposes a new, integrated methodology for preliminary assessment that considers a three-stage process that involves the following: (1) traditional empirical relationships for predicting ground movement from tunneling, (2) recent advances in condition assessments, and (3) architectural designators related to usage and historic preservation listings. The methodology is applied to a study area of nearly 260 buildings in the city center of Dublin Ireland, in an area slated for an upcoming metro. The results are com-pared to the Environmental Impact Statement issued for the official project. Al-though the test case is for tunneling, the approach may be adapted to other subsurface construction activities including excavation and piling.

Jan 1, 2009

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 Patrick Granitzki, Alicia Plinio, Janitha Batagoda, Peter Howell

The City of Newark is making a comeback with new mixed-use multi-storied Residential Development projects. The majority of developers tend to use driven H-pile deep foundation systems to support their super-structures. A different approach was recommended for one particular new development near the Passaic River. The surficial geology included glacial deposits consisting of loose to dense sand overlaying relatively soft silt and clay and a lower stratum of medium-dense sand. During a preliminary site investigation for the project, bedrock was encountered at depths ranging between approximately 168 feet to 182 feet below the ground surface. Design capacity required a single pile of 200 tons. Two different pile foundation systems were evaluated in conjunction to the typical driven H-pile system in order to review potential costs and construction schedule impacts. The two alternative pile systems evaluated were tapered tube piles and drilled displacement piles. Theoretical calculations were followed by in-situ load testing. The field testing results indicated the use of drilled displacement piles as the best option for a portion of the proposed building. This paper discusses the different piles systems considered, installation and using drilled displacement piles to minimize cost and optimize construction.

Sep 8, 2021

By Emad Farouz

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.

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 Daniel Magill, Jim Gentry

"Acrylamide chemical grout (C3H2NO) has been successfully used for over 50 years to control groundwater and stop infiltration. This paper will address three unique projects involving the control of groundwater with each study providing special circumstances and geological conditions: encapsulation of radioactive hazardous waste in the United States, a tailings dam for a large copper/gold mine in Argentina and 27 miles of leaking subway in Canada. The primary reasons for selecting acrylamide grout were based on the following characteristics: thinnest chemical grout on the market, a true solution grout which contains no suspended solids in the blended product, flexible gel set times, and a 362 year half-life in soil as determined by the U.S. Department of Energy.INTRODUCTIONChemical grouting has been successfully used for over fifty years to control the movement of groundwater in a wide variety of applications including:•, Hazardous Waste Containment•, Subways & Tunnels•, Mines & Tailings Dams•, Concrete & Earthen Dams•, Underwater Structures•, Beneath/Around Underground Structures•, Mainline Sewers, Laterals, Manholes•, Large Soil Stabilization ProjectsThis presentation will review three projects where chemical grout was utilized to address some very difficult water control challenges, each providing special circumstances and geological conditions:1. Pre-construction seepage control at a mine tailings dam2. 27 miles of leaking subway3. Encapsulation of radio-active hazardous wasteThe reasons for selecting acrylamide grout as the solution for controlling groundwater in these selected projects were based on the following characteristics:1. Acrylamide grout is the thinnest chemical grout on the market2. No suspended solids which allows acrylamide grout to travel anywhere water can travel3. Flexible gel set times from 5 seconds to 10+ hours4. U.S. Department of Energy studies conclude that acrylamide chemical grout has a 362 year half-life in soil and can reduce the permeability of rock/soil to less than 10-8 meters per second (m/s)"

Jan 1, 2017

By George Gazetas, Sissy Nikolaou, Fani Gelagoti, Irene Georgiou, Rallis Kourkoulis

"The need to shift geotechnical design from a “factor of safety” to a “performance based” design (PBD) approach has increased rapidly in the past years following examples from structural engineering. PBD supports sustainable engineered systems that target project-specific geotechnical behavior objectives and results in more rational and, in most cases, less conservative solutions. Resiliency, efficiency, risk optimization, and cost-effectiveness are key components of this approach. For design of retaining walls, the concept of mechanically stabilized earth (MSE) systems combines these attributes, while being environmentally friendly and adaptive to variable construction conditions. Natural hazards, such as earthquakes, may drive the design of MSE systems whose reliability depends on their performance under extreme events. In this paper, the authors compare the seismic response of an MSE steel-reinforced vs. concrete-reinforced retaining wall. The MSE system is composed of a grid of longitudinal and transverse ribs which internally enhances the capacity of the soil backfill. Results of fully non-linear twodimensional (2-D) numerical finite element analyses using two commercial programs with emphasis on the interface conditions are presented. The pull-out resistance of the grid used in the numerical simulation was evaluated from actual pull-out experiments. The results demonstrate a superior performance of the MSE system as compared to the concrete one, especially when subjected to strong seismic excitations.INTRODUCTIONThe idea of performance-based geotechnical engineering is not new, and has been evolving as our perception for ‘good’ performance has also evolved (Kramer, 2008). In early practice, the only criterion for achieving good performance was to avoid failure; designers had only to ensure that the available capacity of the geotechnical system is sufficiently higher than the expected demand (i.e. Load and Resistance Factor Methodologies). Yet, even when the key design requirements against collapse are satisfied, the system may still be placed into a condition in which the deformation constraints are not met (Bolton, 2012). To address these issues, geotechnical design has been developing into a predominantly performance-based approach that correlates deformation considerations to the severity of the experienced loading. As such, in earthquake-related problems, the definition of good performance of a geotechnical system is no more unique; for a low intensity earthquake the system should remain serviceable (i.e., the developed deformations should remain low), whilst for the design earthquake the maintenance of lifesafety is the single performance criterion."

Jan 1, 2016

By Nicholas P. Gura

This paper presents the analysis, design, and load test program results for drilled shafts to support a 70-story hotel tower and associated 10 story podium structures located in Las Vegas, Nevada. A mat foundation for the structure, although feasible, would have produced undesirable differential settlements within the high rise tower footprint and at the interface with adjacent lower level podium structures. The resulting foundation system solution for the 70-story, approximately 800-foot long hotel tower was four-foot diameter drilled shafts, extending 100 below shaft cutoff. The design compression capacity for the four foot diameter drilled shaft was 5,000 kips. The load test program proved that the unique Las Vegas valley geology lends itself to efficient installation, precluding the need for engineered slurry or casing. The load testing program included the installation of two four-foot diameter test shafts to 100 feet below theoretical cutoff and the performance of two highly instrumented independent Osterberg load cell tests with maximum sustained test loads of 12,000 kips. Sonic caliper testing was also performed to document actual in-place shaft diameters and verticality. The load test program also provided information necessary for the foundation design of the podium structures. In addition to the tower?s drilled shaft load test program data, continuous flight auger (CFA) pile evaluation and testing was also performed. The CFA testing consisted of traditional ?top down? loading techniques and was performed as an alternative to the recommended shallow drilled shafts for the lower level podium structures. The results of the CFA test program provided supplemental, insightful soil friction data which was used in conjunction with the drilled shaft test program data in evaluating the most appropriate support for the lower level structures.

Jan 1, 2007

By Ali Ebrahimi, Jeremy M. Gasser, Cuneyt Gokmen, Paul J. Sabatini, Roneet Das, William Tanner, Amir Ahmadipur

There are safety concerns related to operation of heavy equipment over coal combustion residual (CCR) impoundments during construction of the impoundment closure programs. As part of a pilot study prior to a full-scale closure construction, an access pathway and working platform were designed and constructed to facilitate equipment access for construction of deep soil mixing (DSM) zones on the ash delta of a CCR impoundment. The access pathway and working platform was constructed using shallow mass mixing with cement at the CCR surface to address safety concerns related to the geotechnical behavior of CCR. This paper describes the data from the instrumentation system which was implemented to monitor the geotechnical performance of the CCR during the pilot study. The instrumentation system included monitoring of the ground movement, vibration, and porewater pressure within the ash delta of the CCR impoundment during a pre-construction load testing, equipment mobilization over the access pathway, and DSM column installation over the working platform. INTRODUCTION A deep soil mixing (DSM) pilot study was conducted at a coal combustion residual (CCR) surface impoundment to evaluate mix designs and construction techniques for the regulatory closure. The DSM columns will create a wall which will separate and retain the CCR in a consolidated footprint separate from the closure by removal portion of the footprint and provide a barrier between the two areas of the surface impoundment. Historically, the surface impoundment received CCRs including fly ash, bottom ash, boiler slag, and gypsum, along with other byproducts produced from flue gas desulfurization (FGD). The predominant CCR in this impoundment were fly ash and bottom ash. The primary goals of the DSM pilot study were to assess the mix design strengths and to evaluate DSM construction techniques that could reach the design mixing depths of up to 90 ft. The DSM test columns were installed on the CCR delta approximately 500 ft from the nearest impoundment dikes. Another objective of the pilot study was to develop, construct, and monitor an access pathway for safe passage and movement of construction equipment on the CCR delta.

Jan 1, 2019

By Yazen Khasawneh, Osvaldo P. M. Vitali, Mohammad Nassim

Wind turbines are subjected to complex form of cyclic loadings with variable amplitudes and frequencies. The cyclic loading and the accumulation of plastic strains with the number of cycles will result in degradation of the foundation soil stiffness. The foundation stiffness degradation will result in a shift (reduction) of the fundamental frequency of the wind turbine. Although this issue is recognized in the guidelines for wind turbines foundation design, no specific provisions are provided in the guidelines to consider the long-term stiffness degradation. In this paper, a practical procedure to consider the long-term cyclic loading effects on the stiffness of wind turbine foundations in cohesive soil is proposed. The procedure is based on 3D FEM modeling and reliable empirical methods to estimate the stiffness degradation due to the cyclic loading. Using the proposed procedure, the long-term performance of the P&H tensionless pier foundation with and without a reinforcing collar at the top of the pier is assessed. The numerical results demonstrated that the long-term performance of the P&H tensionless pier foundation with a reinforcing collar at the top of the pier is outstanding with negligible long-term degradation of the foundation stiffness.

Sep 8, 2021

By James M. Tantalla, Dwight Metcalf, Roderic A. Ellman Jr.

"The construction of a new low head hydro-electric plant at the Cannelton Lock and Dam required the design and construction of a cofferdam to accommodate a deep excavation extending approximately 150 feet below the Ohio River levels. The new plant, which generates about 390 GWh of electricity annually, is owned by American Municipal Power (AMP). A specialist team was assembled to design and construct the cofferdam, marine dike and CB slurry wall that helped make the project successful and on time for project delivery.Because the new plant diverts water from the locks and dam through a powerhouse to generate power, it would need to be partially in the river to operate properly. To accomplish this, approximately 250,000 square feet of land was reclaimed from the river by construction of a marine dike. The dike, combined with the design and construction of a 150 foot deep cement bentonite (CB) cutoff wall enabled construction of the new plant in the dry. Extensive dewatering analyses were performed using Modflow to evaluate pumping requirements and the number of wells needed to maintain ground water at required levels within the side slopes and final subgrade. A monitoring program consisting of inclinometers, piezometers and movement monitoring points were used to monitor cofferdam stability and performance throughout construction. Detailed two and three dimensional stability analyses that included a parametric study of fluctuating river levels and slurry unit weight were performed to ensure stability and suitable low permeability of the trench during cut-off wall excavation both on land and in the marine dike. The wall was constructed with both a hydromill excavating primary panels and a clamshell following behind to construct secondary panels. Data acquisition systems onboard the excavating equipment allowed for detailed confirmation of the continuity of the wall at each interface between panels. Another challenging aspect was the CB mix design for the trench. The cofferdam required the construction of a 1,300-foot long marine dike downstream of the existing dam up to 100 feet tall founded on existing river sediment to enclose the site and cut-off the seepage into the excavation from the river. Marine dike construction utilized vibro-compaction to pre-densify granular fills placed underwater through which the CB trench extended."

Jan 1, 2016

By Yazen Khasawneh, Osvaldo P. M. Vitali, Mohammad Nassim

The demand for renewable energy is growing as the conventional energy resources are becoming more limited and we are more conscious about the negative impact of conventional energy sources on the environment. Wind turbines technology is evolving in a fast pace, the towers are becoming taller, and the rotors are getting larger. The challenge is to maintain the Levelized Cost of Electricity (LCOE) as low as possible to ensure a sustainable and an economically feasible energy supply. Thus, the foundation systems for wind turbines should evolve to meet the increasing load demand, while reducing the LCOE. In this paper, an innovative foundation system for onshore wind turbines is presented. The new foundation system is the conventional P&H tensionless pier foundation (PHTP) with a reinforced concrete collar at the top of the pier. 3D FEM modeling was conducted to assess the benefits achieved by adding a collar at the top of the PHTP foundation. The numerical results show a significant performance enhancement of the proposed foundation system over the conventional PHTP foundation. The enhanced foundation system also has an economical advantage because the depth of the pier can be greatly reduced while maintaining a superior performance.

Sep 8, 2021

By Maurizio Siepi, Paul van Horn, John Coupland, Julian Crawley

"TTMJ is the acronym for the Slurry (Diaphragm) Wall Tension Track Milled Joint currently in development as part of the European Union's innovative and far-reaching Horizon 2020 initiative (FTI Pilot-2015-1 720579). The TTMJ Project has been specifically set up to deliver this versatile new step-forward in Slurry Wall technology. The TTMJ System is protected by patent in Europe and the USA, and is currently under development by a consortium comprising Trevi SpA (Italy), Arup (Netherlands) and CCMJ Systems (UK). The principles of the TTMJ System together with the installation process are herein described in general terms. The system is still under development with field trials scheduled for early 2018, so some of the detail will not be disclosed at this stage. It is the intention of the Authors that the results of these field trials and a more complete description of the System will be presented in a paper we intend to submit for the DFI/EFFC International Conference on Deep Foundations and Ground Improvement to be held in Rome, Italy in June 2018. The final section of this paper explains how the TTMJ system can be applied to a common application of slurry wall construction; deep circular or multi-cell shafts. The system can be used to construct shafts more easily and at less cost than current methods. It also allows shafts with smaller internal dimensions to be constructed than is currently practical.INTRODUCTIONCCMJ Systems (UK) realised that an innovative new approach to forming joints in both Slurry (Diaphragm) Walls and Secant Pile Walls would provide greatly improved joint integrity to greater depths, to the overallbenefit of retaining wall quality, across the world-wide foundations industry.In particular this new system is designed to:??Increase the effective depth range of Slurry Walls (especially walls excavated by grab) and Secant Walls??Remove the requirement for Stop-ends or Joint Formers??Allow for a Shear Key at the joint??Allow for a Water Stop to be installed at the joint??Permit Continuous Reinforcement across the joint??Optimise Reinforcement Density and hence Concrete Flow??Facilitate joints in corner panels eliminating the need for “L” shaped cages and reducing largesingle-pour concrete volumes and slurry storage capacity requirements.??Enable the construction of smaller-dimensioned square and circular deep shafts (especially useful for city-centre sites) than is possible with current methods.CCMJ Systems approached other industry specialists with a view to forming a development team to explore the possibilities for this new technique."

Jan 1, 2017

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 Arash Khosravifar, Nason McCullough, Stephen, Milad Souri, Scott Schlechter, E. Dickenson

The results of five centrifuge models were used to evaluate the response of pile-supported wharves subjected to inertial and liquefaction-induced lateral spreading loads. The centrifuge models contained pile groups that were embedded in rockfill dikes over layers of loose to dense sand and were shaken by a series of ground motions. The p-y curves were back-calculated for both dynamic and static loading from centrifuge data and were compared against commonly used API p-y relationships. It was found that a significant reduction in ultimate soil resistance occurred in dynamic p-y curves in partially/fully liquefied soils as compared to static p-y curves. It was also found that incorporating p-multipliers that are proportional to the pore water pressure ratio in granular materials is adequate for estimating pile demands in pseudo static analysis. 1. INTRODUCTION Liquefaction-induced ground deformations can cause severe damage to pile-supported wharves and other waterfront structures. A common approach in analyzing the lateral behavior of piles against seismic loads is using the beam on nonlinear Winkler foundation (BNWF) or p-y spring analysis. One common p-y relationship for sand is the one proposed by the American Petroleum Institute, also known as the API sand model (API 1993). While the API sand model was originally developed for the static loading conditions, it is common to modify the API sand curves for the effects of cyclic loading. However, there is no consensus on how to modify the static p-y curves for the effects of liquefaction and pore water pressure generation in loose granular soils. In previous studies, p-y springs of piles in liquefying soils were back-calculated from case histories, centrifuge model studies (e.g., Wilson et al. 2000; Brandenberg et al. 2005; Abdoun et al. 2003), full-scale tests (e.g., Rollins et al. 2005; Chang and Hutchinson 2013), and numerical analyses (e.g., McGann et al. 2011). In general, these studies found the softening effects of soil liquefaction on p-y curves, as well as a hardening behavior attributed to the dilative response of the liquefied soil around the pile. However, these studies provide varying recommendations on how to modify the static p-y curves to capture this complex behavior. Some design guidelines propose softening the static p-y curves using p-multipliers (e.g., Caltrans 2012). Other studies propose an upward concave shape for p-y curves in liquefied soils (e.g., Franke and Rollins 2013; Chang and Hutchinson 2013).

Jan 1, 2019

By Benjamin B. Buensuceso III

Crosshole sonic logging (CSL) is a popular quality assurance and quality control method used to examine the concrete quality of cast-in place deep foundations, though the evaluation of the results is subject to certain limitations. One such limitation explored in this paper is the occurrence of false positives, where signal anomalies indicated by CSL test results are not necessarily indicative of imperfections in the foundation that could affect its performance. A case study of false positives evaluated in CSL records in a major infrastructure project in Metro Manila is presented in this paper. A detailed desktop evaluation and results from complementary high-strain dynamic load testing and low-strain pile integrity testing were used to evaluate the significance of the suspected false positive signal anomalies from the CSL test results. Recommendations for the proper interpretation and evaluation of CSL test results in Philippine practice, given the method’s limitations and examples presented, are also shared.

Sep 8, 2021

By Harald Vogel, Johannes Lachenski, Friedemann Koetzel, Sebastian Schnell

In this paper, a digital subsoil approach, a work-in-progress, will be presented describing the transformation from a classical 2D to digital 3D thinking process in the design of geotechnical structures. Certain pitfalls as well as lessons learned are described, and the reader can understand that the digitalization process of the design of geotechnical structures is always a problem-focused approach by creating systems for certain processes rather than setting rules or regulations. Three project examples are presented. Two of the presented project examples feature a heterogeneous geology distribution and made it necessary for the design of the foundations to work with 3D subsoil and 3D calculation models. However, the digital 3D design process in the third project, an inner-city excavation pit, is driven by the complicated boundary conditions making it necessary to work in a parametric 3D design space. All projects have in common, that new processes had to be developed. The paper concludes with a flow chart describing the process of the elaborated digital subsoil approach.

May 1, 2022