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By Mohini Patel, Jahnavi Parmar, Pranav R. T Peddinti

Expansive clays pose a variety of geotechnical problems. Although the admixture stabilization is proven to address their problematic swelling and shrinkage characteristics, the influence of unsaturated condition on the engineering performance of these soils needs further research attention. In addition, highly saline soils with high organic content would further alter their performance. A similar soil stratum was encountered at the Gulf of Cambay, Bhavnagar district, India. High salinity in the in-situ expansive soil of basaltic origin and the prevailing unsaturated condition, enforces the engineers to look out for possible soil treatment methods. In this regard, the present work attempts to analyze the unsaturated behaviour of this soil when fly ash is used as an admixture. A comparative study for stabilized and unstabilized mixes is performed in terms of their unconfined compressive strength, electrical conductivity, swell characteristics and California Bearing Ratio.

May 1, 2022

By Sushant Upadhyaya, Deniz Karadeniz

As part of the widening of I-64 in Williamsburg, Virginia, an extensive subsurface exploration program consisting of Standard Penetration Tests (SPT), Cone Penetration Tests (CPT), Dilatometer Tests (DMT), and Vane Shear Test was performed. In addition to these in-situ tests, an extensive laboratory testing program was completed including Consolidated-Undrained Triaxial, Unconsolidated-Undrained Triaxial, Direct Shear, and consolidation tests. The strength and the compressibility properties are deemed conservative for Yorktown and St. Mary’s Formations when evaluated based on the current topography, the existing overburden pressure and SPT values. SPT exhibited low blow counts especially within Yorktown Formation due to the increased excess pore water pressures resulting in a localized liquefaction at the tip of the split spoon sampler corresponding to remolded or fully softened strength of the soil. Therefore, the applicability of the SPT correlated soil parameters somewhat leads to conservative designs with deeper piles to achieve a desired structural load demand. Generally, the in-situ estimated soil design parameters are found to be comparable with the laboratory test results corresponding to long-term resistance gain with time. It is of practical importance to employ realistic soil design parameters for design applications such as pile foundations to provide cost and schedule savings. This paper presents a discussion on the soil strength estimates and variability from in-situ and laboratory tests for realistic strength characterization of Coastal Plain deposits.

By Michael Shedlosky, Sonia Sorabella Swift, Nina Carney, David Tarasovic

Rigid inclusions were used to support roadway fills and mechanically stabilized earth (MSE) walls for the South Capitol Street Corridor project. The first phase of this two-phase, nearly $1 billion project will include the replacement of the Frederick Douglass Memorial Bridge, including two approach ovals east and west of the Anacostia River, the replacement of the I-295/Suitland Parkway Interchange, and the construction of several traffic ramps. The bridge itself carries over 70,000 drivers daily and is expected to open in 2021. Ground improvement is required over a portion of the project footprint. Within the ground improvement area, the construction includes MSE walls up to 35 feet high and embankment fills up to 28 feet for which CMC rigid inclusions (RIs) were used to mitigate settlement and stability. The proposed construction runs over multiple old, in-service utilities that the project requirements indicate could not tolerate any stress or settlement due to the construction. As such, solutions that spanned the utilities were required. A concrete slab of varying thickness was used to span a fragile 108-inch-diameter sewer pipeline and 48- inch-square-precast-concrete box beams were used to span twin utilities that were buried just a few feet below current working grades on site. Unreinforced RIs were used to support these structures. The center to center spacing of the RIs perpendicular to the pipe run was 26.5 ft for the concrete slab and 62 feet for the precast--concrete box beams. The axial forces on the RIs were up to 267 kips. The RIs were not structurally connected to the slab or box beams. A single-element load test was performed to confirm the load-carrying capacity of the RIs. This paper will focus on the utility protection slab over the twin utilities and provide an overview of the design of the structural and geotechnical solutions and will present the results of the load test performed. INTRODUCTION The new Frederick Douglass Memorial Bridge (FDM Bridge) and reconstruction of the Suitland Parkway/ I-295 interchange (South Capitol Project) is a part of the Anacostia Waterfront Initiative (AWI) Program, whose goal is to transform the shores of the Anacostia River. The existing FDM Bridge is approximately 70-years old and has been classified as “functionally obsolete”. The completed South Capitol Project will improve the multi-modal transportation options, increase pedestrian and vehicular safety and provide additional green space. The proposed FDM Bridge, a rendering of which is shown in Fig. 1, is designed to become a landmark bridge in the Washington, D.C. area.

Jan 1, 2019

By Brian J. Olson, Kevin Haiar

Originally constructed between 1939 and 1941 as part of Franklin D. Roosevelt’s New Deal programs, the Bonneville to Hood River 115 kV Transmission Line required an infrastructure upgrade to remain reliable and in-service. The line traverses the rugged landscape of the Columbia River Gorge on the Oregon- Washington border, featuring steep, talus slopes; uneven, rocky terrain; and a variety of environmental sensitivities. This paper details the design and construction of 27 micropile foundations for new, fire- hardening steel poles through a particularly challenging stretch of the alignment. The difficult access and environmental constraints at these sites designated them as helicopter-accessible and precluded the collection of detailed geotechnical information prior to construction. Micropiles provided a viable foundation alternative due to their portability and flexibility during construction. Detail will be provided on the extensive preliminary desktop study performed, as well as the process of developing engineering designs to successfully accommodate for variability and unknowns in complex geological conditions. With an increasing number of electric power projects traversing challenging terrain and facing similar obstacles, this project stands to provide valuable lessons learned to the industry.

Sep 8, 2021

By Prodyot Kumar Ray, Sudip Kumar Koley, Aminul Islam, Somnath Banerjee

One of the most important topics in the construction industry is the building of railway embankments. Being such a delicate and significant structure, it is crucial to properly design the embankment and build it while adhering to all statutory criteria and design guidelines. A railway embankment's subsoil condition and fill material, groundwater table, dynamic and static loads during operation, and embankment geometry are some of its most crucial design considerations. This paper discusses the likely causes of the collapse of a railway embankment in eastern India as well as the suggested rehabilitation scheme. It was observed that an embankment collapsed in the aforementioned area during a inccesent rain. Along with the side shifting of a cantilever retaining wall that was positioned at the bottom of the embankment, the embankment next to the railroad track settled vertically. According to the available geotechnical report, the sub soil strata in half of the area adjacent to the embankment profile, where the embankment height gradually decreases from maximum height, is stiff to hard clay with an undrained cohesion value of around 50 kpa followed by dense sand, and the sub soil strata in the other half is soft clay with an undrained strength of 15 kpa. As a result, in the rainy season due to the sudden increase in the water table, the self-weight of the embankment increased and further caused the under-laying soft clay to get squeezed away and settle. Due to this squeeze/settlement effect of the soft clay layer, the retaining wall got disturbed along with the generation of an undulated embankment top profile. As a remedial measure, it is proposed to construct a contiguous bored pile wall at the toe of the embankment to stabilize the slope, and additionally, compaction grouting is recommended beneath the embankment to improve the soft clay. In order to carry out the analysis, certain commercial geotechnical software like Slide, Wallap, and Plaxis 2D are used. The factor of safety of the embankment slope considering the above restoration scheme is adequate under static and seismic conditions.

Sep 1, 2022

By Nozomu Kotake, Rakshya Shrestha, Ralph Griffin, Stefanos Papadopulos, Jeff Fippin, Sushil Kafle

Direct Power Compaction (DPC) is a deep Vibro-compaction method used for liquefaction mitigation. In DPC, H-beams are used as vibrating rods penetrating deep into the ground, and a vibrating force is applied directly to the tip of these H-beams to densify the loose ground. A characteristic feature of DPC is the use of a flapping plate installed at the base of the H-beam to enhance the compaction efficiency during penetration. In addition, 2-rod and 4-rod type equipment have been developed to improve productivity and enable rapid construction. DPC was selected as the most suitable and cost-effective technique to mitigate liquefaction hazards in two projects in the San Francisco Bay Area, one on Alameda Island and another on Treasure Island. Both sites were capped with hydraulically placed sand fills. Liquefaction analyses indicated excessive liquefaction-induced settlements and large lateral spread without ground improvement. Densification using DPC was performed up to depths of 42 ft to reduce the liquefaction potential of the sand fill to acceptable levels and to allow planned improvements. Cone penetration tests were conducted before and after DPC to evaluate its performance. This paper describes the equipment and process involved in DPC and discusses its application in terms of subsurface conditions and geotechnical design considerations.

Sep 8, 2021

By Daniel P. Stare, Lucian P. Spiteri, Christopher M. Hallahan, James C. Myers

Buckeye Lake Dam was substantially remediated between 2015 and 2018 as a result of unacceptable dam safety performance. A permanent seepage cutoff, consisting primarily of a soil mixed cutoff wall (SMCW) with occasional sections of steel sheet piling, was constructed along the dam alignment. Closures were required at the terminus of the soil mix elements with existing structures or coffer cells, and at locations where new sheet piling was constructed parallel to the new soil mixed cutoff wall, creating a short circuit seepage path. The original proposed design to construct these closures included permeation grouting methods with chemical grouts. However, a combination of multiple chemical grout types, multiple grout pipes, and an extensive post-grouting verification program was required to ensure the design intent was achieved. After award of the project, the specialty grouting contractor elected to evaluate jet grouting as an alternative closure construction method. The advantages of the jet grouting option offered potential schedule and cost savings to the project as well as a superior product for seepage reduction, given the mixed soil conditions at the site. This paper presents an examination of the site conditions and project goals for the construction of the proposed closure elements for the rehabilitation of Buckeye Lake Dam. Descriptions of the original and alternative treatment methods are provided, with expected performance results. A description of the relative strengths and deficiencies of each method, as well as the feasibility and constructability of each method is provided. The implementation of the jet grouting program is presented, including a discussion of the design elements, quality control test methods, movement monitoring, and verification test methods. This paper also examines the risks associated with jet grouting and how those risks were mitigated during the grouting operations. HISTORY Buckeye Lake is situated approximately 28 miles east of Columbus, Ohio and is managed and operated by the Ohio Department of Natural Resources (ODNR) as part of the Ohio State Parks system. The lake is impounded by natural features that exist along the south and east banks of the reservoir, and by the embankment structure constructed along the north and west banks of the reservoir (see Fig. 1). The reservoir site was originally a natural swamp and the original purpose of the constructed dam and reservoir was to provide water to the Ohio and Erie Canal System. Several dam alignments and configurations were constructed during its early history; however, the original embankment is comprised of homogeneous earthen fill. The embankment is 15 ft (4.6 m) high and extends 4.1 miles (6.6 km) from the North Shore abutment along the east, continuing to the abutment at Lieb’s Island to the West. Several spillway and outlet structures exist along the embankment alignment. Most noteworthy are Seller’s Spillway and Amil Spillway. Fig. 2 is a Plan View of the embankment alignment and appurtenant structures at Buckeye Lake.

Jan 1, 2019

By Rick Deschamps, Amanda Blank, Matthew W. Drewek, Michael P. Walker

The Prairie du Sac Dam, located on the Wisconsin River, northwest of Madison, Wisconsin, was constructed 1912-1914. The spillway is an Ambursen-type, consisting of a series timber pile supported pier and buttress walls and rollway slab. The timber piles supporting the spillway, numbering approximately 5,000, have deteriorated, and the spillway structure was underpinned with over 700 micropiles as part of a design-build construction project. The underpinning micropiles needed to be arranged to avoid interferences with the existing timber piles, requiring the micropiles to be installed in the open spaces between the piers and buttresses. Inevitably, the installation of the new micropiles encountered obstructions, including existing timber piles out of alignment, as well as timber piles used to support the original construction activities and sheet pile used to control water during the original construction. This paper discusses using finite element analysis to model the spillway structure to estimate the vertical and horizontal stiffness with an extensive sensitivity analysis was performed during the design phase to account for anticipated construction challenges and potential variations in the underpinning performance. The inherent rigidity of the spillway structure allowed for load distribution to the underpinning system even when new micropiles needed to be re-located and aligned to avoid interferences with existing timber piles and other abandoned foundation elements dating back to original construction.

Sep 8, 2021

By Amalia Giannakou

When designing structures in seismically active areas, foundations of critical structures are typically located away from known faults. Indeed many seismic codes prohibit construction in the immediate vicinity of seismically active faults establishing minimum setbacks from the faults. However, for long structures such as bridges, tunnels and pipelines, a fault maybe unavoidable, and fault rupture risk impossible to preclude. This paper presents a case study of a bridge foundation design that incorporates the consequences of fault deformations passing through the foundation. A series of site surveys were conducted to characterize the fault environment, and fault displacement hazard analyses were conducted to develop design displacement demands. Subsequently, numerical analyses were performed to evaluate the fault rupture-induced demands on a pier foundation in terms of displacements and rotations. Initially, analyses were performed that model the free field fault rupture propagation to the ground surface of the fault to ensure that the basic site characteristics are captured. Subsequently, the foundation elements were introduced in the model and the fault rupture is simulated again. The interaction and influence of the foundation on the fault rupture propagation is calculated, and the consequent demands and distortions of the foundation block provide a basis for structural engineers to design the bridge.

By A. Fisher

The use of thermal integrity testing to verify the quality of deep foundations has increased significantly in the UK and other world markets over the last 5 years. The introduction of distributed fibre optic sensing to this field has broadened the range of applications in which it can be deployed and the types of foundations which can be tested. This paper presents how fibre optic sensing technology can be successfully deployed in the construction environment the range of foundation techniques to which it can be applied. Alongside developments in the practical aspects of thermal testing, progress has been made in establishing assessment criteria which can be used to evaluate the results. This paper presents recent examples of comparative studies on foundations which include both thermal integrity testing, cross hole sonic logging and intrusive coring. The use of distributed strain measurement during pile load testing presents an alternative means to verify the assessment criteria used for integrity testing. This new approach can achieve comparable results to foundation exhumation or intrusive investigation and at a fraction of the cost. This paper presents the findings of several such studies, highlighting the benefits and opportunities for future improvement of the method.

Oct 1, 2022

By Mu Chen, Ye-Shuang Xu, Dong-Wei Hou, Shui-Long Shen, Huai-Na Wu

"This paper presents a laboratory investigation on the mechanical behaviors of the cement-clay admixture improved by polypropylene fiber. Cement can significantly improve the clay admixture. The fiber additive also improves the strength and ductility of the improved clay. The Unconfined Compression Strength (UCS) of the polypropylene fiber-reinforced cement-clay presents an overall trend to grow with the increase of fiber length. The improved clay reached its peak strength at the fiber content of 0.5%. Then the UCS of the improved clay will slowly reverse if the fiber content continues to rise. For study of curing time, improved clay behaves better in its early strength, but an inhibition will be brought about if fibers are excessive.INTRODUCTIONGround improvement technology is essential for construction of structures in soft ground. Some traditional techniques often cost much but result in little. For instance, along the coastal region of China, soft ground is often improved by backfill with high quality sandy soil transported far away, leading to high additional haulage costs and long construction period. Reutilizing the excavated soil as backfill or subgrade after treatment, by contrast, will be more economical and effective (Hufenus et al., 2006). Many researches have been conducted to improve the compression strength of soft soil, among which, the method of mixing the soft soil with cement and fly ash is one of the most common ways (Kolias et al., 2005; Horpibulsuk et al., 2009; Porcino et al., 2012). It is known that soil resists well against compression and shear force but behaves poorly in resistance to tension. Therefore, utilizing tensile elements such as fibers and strips to improve the tensile strength will be effective because of its strength isotropy, better durability and cost effective (Haeri et al., 2000; Kaniraj and Havanagi, 2001; Consoli et al., 2010)."

Jan 1, 2015

By Emilie Lapointe, Fernando Famania

"A reliable determination of the in-placed cement factor, as defined by mass of cement over volume of final element of treated soil, allows the optimization of cement usage to achieve treated soil requirements. Cement determination tests were performed on soil-cement samples, both fresh (as per ASTM D5982) and hardened (as per ASTM C1084). This paper reviews the calibration work required for the D5982 determination of cement content by the heat of hydration method used on soil-cement samples obtained by wet-grabbing. Using the correlation curves in the field provides a rapid assessment of cement content hence optimizing the cement injection rate to match laboratory tests previously conducted. Cement determination tests on hardened soil-cement specimens from wet-grabs and cores were performed using the oxides method. Samples, both cored and wet-grabbed, were tested in a given cement-treated element, and in different soils to inform on the expected variation in cement content from field installation. Results indicate that both cement determination methods are valid for forensically determining cement contents and that they provide better assessment than the conventional field reporting methods. The methods can be used to optimise the cement usage as well as for Quality Assurance, especially when coring quality is poor.INTRODUCTIONThe degree of improvement, and inherent strength, which is attained in a deep-mixed soil is a function of many factors. The binder type, the existing soil, the mixing conditions and the curing conditions are the categories of factors influencing the strength of a given cement-treated soil as agreed by the deep mixing community and as summarized by the Coastal Development of Technology [CDIT] (2012). Given a site with existing soils and conditions requiring soil improvement using a given binder, the designer and/or contractor can control the mixing conditions. Mixing conditions are inclusive of the degree of mixing, mixing duration and the quantity of binder. Once a deep mixing method has been chosen to mix optimally the in-situ soil, the quantity of binder is the only remaining factor to be optimized. The quantity of binder, in the construction industry is commonly referred to as the field binder factor [ar] and defined by the mass of binder over the volume of soil treated with kg/m3 as unit. In research, the quantity of binder is referred to as the binder content [Cc] and expressed as a ratio of the mass of binder over the mass of dry soil mixed."

Jan 1, 2015

By Orestis Zarzouras, Amalia Giannakou, Jacob Chacko

"When designing structures in seismically active areas, foundations of critical structures are typically located away from known faults. Indeed many seismic codes prohibit construction in the immediate vicinity of seismically active faults establishing minimum setbacks from the faults. However, for long structures such as bridges, tunnels and pipelines, a fault maybe unavoidable, and fault rupture risk impossible to preclude. This paper presents a case study of a bridge foundation design that incorporates the consequences of fault deformations passing through the foundation. A series of site surveys were conducted to characterize the fault environment, and fault displacement hazard analyses were conducted to develop design displacement demands. Subsequently, numerical analyses were performed to evaluate the fault rupture-induced demands on a pier foundation in terms of displacements and rotations. Initially, analyses were performed that model the free field fault rupture propagation to the ground surface of the fault to ensure that the basic site characteristics are captured. Subsequently, the foundation elements were introduced in the model and the fault rupture is simulated again. The interaction and influence of the foundation on the fault rupture propagation is calculated, and the consequent demands and distortions of the foundation block provide a basis for structural engineers to design the bridge.IntroductionThe Izmit Bay bridge, a 3-km-long suspension bridge that crosses Izmit Bay in Turkey, is planned to be constructed in one of the most seismically active places in the world. The south approach structures for the Izmit Bay Bridge along the western side of the Hersek peninsula bring the bridge down from on the order of El. 60 meters at the South Anchorage to an elevated embankment approximately 1.3 km farther south (Figure 1). The south approach structures are located within a zone of secondary deformation around the primary trace of the North Anatolian Fault. The concept design team has developed a concept design for a “viaduct” structure that consists of 10 spans with lengths varying between 136 m and 100 m and two back spans one of 125 m, attached to the main bridge and the other of 74 m attached to the south embankment."

Jan 1, 2017

By Eric P. Bregman

As part of an on-going effort to improve water quality and reduce discharge into Boston Harbor, the Massachusetts Water Resources Authority (MWRA) East Boston Branch Sewer Relief Project was designed under a Federal mandate from the United States Environmental Protection Agency (EPA) to upgrade the aging sewer system, increase system storage and greatly reduce the volume of combined sewer overflows into the Harbor. The project scope of work includes the installation of over 2 miles (11,800 linear feet) of 36-inch and 66-inch diameter sewer relief piping, twenty (20) temporary shafts and an approximate 100 foot open cut section, located within the densely populated neighborhood of East Boston, Massachusetts. This area is a former marshland backfilled in the early to mid 1800?s where busy commercial streets co-mingle with thickly settled residential houses. The subsurface conditions present within Boston?s complex geology include the presence of subsurface contamination as well as complex networks of underground utilities. Additional site limitations included low headroom, noise, and traffic restrictions. Together these limitations required the design of individual earth support systems, tailored for each shaft location. Moreover, challenging subsurface conditions identified during construction required design modifications to minimize cost and schedule impacts related to construction dewatering, treatment of contaminated groundwater, internal bracing, and utility relocations. This paper provides a case history of the Geo-structural design and performance of various earth support techniques utilized to construct jacking and receiving shafts designed to launch and receive two (2) micro-tunnel boring machines (MTBM) and to support the construction of new deep shaft structures in an urban coastal area.

By Eric P. Bregman, Franklin M. Grynkewicz, John E. Regan

"As part of an on-going effort to improve water quality and reduce discharge into Boston Harbor, the Massachusetts Water Resources Authority (MWRA) East Boston Branch Sewer Relief Project was designed under a Federal mandate from the United States Environmental Protection Agency (EPA) to upgrade the aging sewer system, increase system storage and greatly reduce the volume of combined sewer overflows into the Harbor. The project scope of work includes the installation of over 2 miles (11,800 linear feet) of 36-inch and 66-inch diameter sewer relief piping, twenty (20) temporary shafts and an approximate 100 foot open cut section, located within the densely populated neighborhood of East Boston, Massachusetts. This area is a former marshland backfilled in the early to mid 1800’s where busy commercial streets co-mingle with thickly settled residential houses.The subsurface conditions present within Boston’s complex geology include the presence of subsurface contamination as well as complex networks of underground utilities. Additional site limitations included low headroom, noise, and traffic restrictions. Together these limitations required the design of individual earth support systems, tailored for each shaft location. Moreover, challenging subsurface conditions identified during construction required design modifications to minimize cost and schedule impacts related to construction dewatering, treatment of contaminated groundwater, internal bracing, and utility relocations.This paper provides a case history of the Geo-structural design and performance of various earth support techniques utilized to construct jacking and receiving shafts designed to launch and receive two (2) micro-tunnel boring machines (MTBM) and to support the construction of new deep shaft structures in an urban coastal area."

Jan 1, 2017

By Dharmil S. Patel, Zoyav S. Benyaminov, Cassandra A. Wetzel

Rehabilitation of the Henry Hudson Bridge is nearing completion, connecting Spuyten Duyvil in the Bronx to Inwood Hill in Manhattan, New York. Constructed in 1936, the Henry Hudson Bridge spans 840 feet over the Hudson River. Challenging geotechnical aspects of this Project required a team of innovators to overcome. Rehabilitation of the existing bridge involved the replacement of sixteen bent pedestal substructures, two abutment pilasters and installation of new deep foundations at the skewbacks. However, the Bridge, roadways, adjacent Metro-North Railroad (MNR) structures and New York City (NYC) Parks land were to remain open to the public for use, with minimal disturbance. In addition to physical constraints, geologic site conditions varied widely across both sides of the River, with varying bedrock quality and depth, greatly impacting the proposed design and construction. Extensive analysis of bedrock conditions was conducted to locate areas of potential wedge failure. The implementation of anchors was used to reinforce rock stability where pedestals and pilasters were replaced. This paper describes several challenging technical and natural aspects overcome in the rehabilitation of the Henry Hudson bridge foundations, including varying geologic site conditions, access restrictions, construction limitations, project specifications and design requirements.

Sep 8, 2021

By Adam Gerondale, David Hemstreet, Lisheng Shao, Kenji Yamasaki

"Foundation soils of a proposed single-span bridge over a busy railroad in Anchorage, Alaska included a layer of sensitive, non-plastic to low-plasticity silt. Slope stability analyses showed that, without ground improvement, the proposed abutments would not be stable immediately following the design earthquake due to the liquefaction of the sensitive silt. Wet soil mixing was selected to mitigate the liquefiable soils and assure abutment stability because: (i) it is a non-vibratory method and can be used for areas adjacent to the railroad tracks and underground utilities, as well as in areas not sensitive to vibration; and (ii) preand post-ground improvement testing, such as SPT or CPT, is not required. Eliminating the liquefaction hazard at the site also allowed for the abutments to be economically supported on shallow spread footings. A total of 511 soil-cement columns were constructed at the two abutments, each with a diameter of 8 feet (2.4 m) and an average length of 20 feet (6.1 m), extending from about 30 to 10 feet (9.1 to 3.0 m) below finished ground elevation. The columns were laid out in a shear wall pattern (in the longitudinal direction of the bridge) to increase stability under the loading by approach embankments.INTRODUCTIONAlaska Department of Transportation and Public Facilities (Alaska DOT&PF) is currently constructing West Dowling Road Overcrossing in Anchorage Alaska. It will be a single-span, steel box girder bridge approximately 200 feet (61 m) long and 100 feet (30 m) wide. It will have approach embankments, about 40 feet (12 m) high, on both sides. It will carry the new extension of West Dowling Road over double tracks of Alaska Railroad and Arctic Blvd. Foundation soils of the abutments consist of surficial fill and peat layer underlain by soft silt which is likely to liquefy and lose strength under shaking by a design earthquake. Both deep and shallow foundations were considered to support the bridge abutments. The design team pursued the option of improving the foundation soils and using shallow footings. Several ground improvement methods were evaluated, out of which wet soil mixing was selected as the best option.In situ wet soil mixing (hereinafter simply soil mixing) is mechanical mixing of soil in its location with cement slurry and produces soil-cement (soilcrete) columns that are stronger, less permeable, and less compressible than the original soil. Soil mixing is used for various applications including reinforcement of soft soils, excavation support, liquefaction mitigation, cutoff walls, etc. This paper presents a case history of soil mixing successfully used to improve foundation soils of bridge abutments to allow the use of spread footings."

Jan 1, 2015

By Rae Mackay, Kaveh Ranjbar Pouya, Ali Tolooiyan

"A major part of Melbourne’s central business district is underlain by a very soft silty clay deposit known as Coode Island Silt (CIS). Due to the low strength of CIS, most construction in the region is based on pile foundation systems. Traditionally, the design of pile foundations is mostly based on empirical and analytical methods. However, numerical methods such as Finite Element Methods (FEM) can be utilised for more accurate estimation of the bearing capacity and deformation of pile foundation systems, especially in complex loading scenarios. Unfortunately, no systematic effort is made yet to calibrate a realistic nonlinear constitutive model to describe the geomechanical behaviour of CIS in a numerically based solution. Among the nonlinear constitutive models, the Hardening Soil (HS) model is an advanced hyperbolic model which accounts for the nonlinearity of stress-strain relationship as well as the stress dependency of the soil stiffness. In this study, the HS model is calibrated based on laboratory tests performed on CIS. Also, to validate the accuracy of the calibration, the wellknown cavity expansion theory is employed to model the CPT cone tip resistance (qc) in CIS, and results are compared against the measured CPT qc profile at the field.INTRODUCTIONA large percentage of world’s coastal areas are covered with soft marine clay deposits. Having very low shear strength and high compressibility, the alluvial deposits are known as one of the most problematic soil layers for the design and construction of infrastructure facilities. A major part of Melbourne’s central business district is underlain by a very soft silty clay deposit known as Coode Island Silt (CIS). Basically, there are two main solutions for construction in such weak soil conditions. One is the use of pile foundations transferring the applied load to deeper and stronger soil layers, and the second one is to employ ground improvement techniques such as using deep soil mixing columns to improve the bearing capacity of the soil. In both cases, a practical geotechnical design should incorporate both stability analysis and deformation analysis to achieve a cost-effective and reliable solution. Most of the classic solutions for stability analyses such as limit equilibrium analysis disregard the stress-strain relationship of the soil for the sake of the simplicity (Chen, 2007; Sokoloviskii, 1965). In a similar simple approach, most of the past studies of deformation analysis have been established on the basis of linear elasticity. However, it is well recognised that the soil stress-strain behaviour is highly nonlinear even at very small strains (Burland, 1989). Hence, for a precise deformation analysis of the foundation of important geotechnical structures, the application of advanced nonlinear constitutive models is extremely beneficial. Precise deformation analysis is essential as geotechnical designers have to predict the displacement of geotechnical structure and the adjacent soil as well as the induced displacement and forces to adjacent structures. This issue is more highlighted recently in the analysis, and design of highly important infrastructures as geotechnical engineers are facing new challenges in the analysis and design of infrastructures in congested areas. Rapid population growth, especially in the major cities all around the world necessitates the design and construction of more integrated infrastructure facilities. Consequently, geotechnical engineers should employ more advanced design approaches to address the new challenges in geotechnical engineering practice. Complicated geometries, different loading scenarios and the application of nonlinear deformation models which is believed to be essential for a precise deformation analysis, necessitate the application of numerical methods to satisfy most of the design requirements."

Jan 1, 1900

By Sitotaw Y. Fantaye

"The first segment of the Second Avenue Subway extension is approaching construction completion. The new extension will operate along Second Avenue from 96th Street to 63rd Street, where it will divert west along the existing 63rd Street line, stopping at the Lexington Avenue/63rd Street Station. The new line will have stateof-the-art stations at 96th, 86th, 72nd and 63rd streets.Most of the two-track, twin-tunnel subway was constructed using bored tunnel methods (Figure 1), with a tunnel boring machine (TBM). The launch and retrieving box of the TBM was strategically located at the south end of the 96th Street Station where bedrock exists approximately 70 ft (21.3 m) below street level. The TBM launch box and the 96th Street Station (Figure 2), including the ancillary facilities adjacent to the station, were constructed by the cut-and-cover method. The cut-and-cover work required the contractor to design and implement a stiff, tightlybraced retaining wall, approximately 100 ft (30.5 m) long, to tie the existing tunnel constructed in the 1970s to the new station, temporary street decking over the entire excavation, and a wide range of excavation support systems at various locations.The cut-and-cover construction posed significant challenges including: installation of street decking on busy Second Avenue, relocation and suspension of the myriad utilities beneath the streets, and configuration of a lateral support system that would minimize movement of adjacent structures but not slow down excavation activities. This article describes the innovative solutions developed to manage and facilitate safe and efficient construction without disrupting Second Avenue, a major southbound one-way thoroughfare.The work was performed in several phases involving: (1) preconstruction condition survey of existing buildings, (2) installation of instrumentation and monitoring, (3) major utility relocation efforts to move vital utilities from within the alignment of the slurry wall on both the east and west sides of the avenue, (4) implementation of maintenance and protection of traffic plans, (5) installation of temporary street decking across the entire avenue and over the excavation to allow an orderly movement of traffic and pedestrians, (6) staged excavation and installation of an intricate temporary bracing system beneath the decking (7) step-by-step construction of the new subway station’s structure and (8) staged removal of the bracing as the structure gained sufficient strength to resist the lateral loads. The main focus in this article is the design and construction of the temporary street decking and lateral bracing systems; the utility suspension system and the north tie-in that allowed the daunting task of excavation and construction of a new subway station in bustling New York City, with minimal disruption to the community, businesses and everyday traffic."

Jan 1, 2016

By Pathik Deb Mallik, Shyamal K. Mitra, Rajiv Kishore, Shuvranshu Rout, Manos De

"This paper presents a case study on the design and construction of a deep underground pit structure constructed inside almost a century old existing plant building. The complexity and challenge for the design and construction lay in executing the work in a difficult subsoil condition especially the presence of deep mica schist. The limited space availability in the existing plant for construction work without hampering regular production in other adjoining areas of the plant made the execution more challenging. Experience with difficult subsoil and proximity to old foundations entailed a non-conventional engineering approach while ensuring complete safety in spite of maintaining the normal operation.INTRODUCTIONTata Steel Processing and Distribution Limited (TSPDL) is a subsidiary unit of Tata Steel Limited (TSL) having a CR processing facility inside the premises of Tata Steel Limited. TSPDL intended to install equipment for a new slitting line inside the existing shed including construction of very deep structure called “loop pit” where the strips from cut CR sheets collect in the form of loops and are recovered as scrap. The entire plant is located within the shed of existing plant. The construction of all foundations including the loop pit is to be executed in the limited area without disturbance to normal production work in balance areas of the plant and also maintain safety and integrity of existing structures.The existing shed is an old structure constructed approximately 80 years ago. The building column foundations are gravity type design of brick masonry supporting only the vertical load from the columns. This type of foundation designed with no eccentricity of loading provides no allowance for implementing any foundation stabilizing design. The present project required civil construction for the new equipment foundations safely within this area."

Jan 1, 2015