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By Ambarish Ghosh, Chitralekha Ghatak, Tanumaya Mitra, Tarun Sengupta, Sajib Das, Sankar Kumar Nath

"Currently construction of important structures like bridges, flyovers and high rise buildings in and around Kolkata are in full swing. These structures have mostly pile or well foundations. The design methodology and construction techniques are being employed keeping in view both the safety and economy of the project. The data presented in this investigation have been taken from Geotechnical Investigation report of Component B in connection with construction of Extradosed Cable Stayed Bridge over River Hooghly in Hooghly and Nadia district of West Bengal, India. The investigation site is located within close proximity of Eocene Hinge Zone which is being taken as the principal contributor of Earthquakes in and around Kolkata. Considering the importance of the project detailed and exhaustive geotechnical investigation has been carried out and site specific response spectra have been generated for analysis and design of the bridge. This paper presents site specific response spectra, liquefaction analysis and comparison of lateral load carrying capacity of pile using Winkler approach and IS 2911 guidelines.INTRODUCTIONPile foundations are used to transfer the load of the super structure through soft soil deposit to deeper bearing stratum by means of skin friction or end bearing or both. Pile foundations are regarded as a safe alternative for supporting structures in seismic areas and have been used for this purpose in non-liquefying as well as liquefying soils. But their design in case of potentially liquefiable soil is quite different from that of non liquefiable soil. In liquefiable soil the progressive buildup of excess pore water pressure will cause stiffness degradation and loss of strength which in turn will induce additional shear force and bending moment in the pile. The mechanism of pile behavior in liquefying soil has been investigated by several investigators in the recent years based on observations of pile performance during earthquakes and studies in the centrifuge and Shake Table tests. Exhaustive geotechnical investigation has been carried out along the proposed alignment of the Extradosed Cable Stayed Bridge i.e., along Baropara, Bansberia ROB, Ishwar Gupta Bridge, Saraswati River to collect disturbed as well as undisturbed soil sample, to develop average soil profile and to determine the design parameters. The proposed project site is very close to Eocene Hinge Zone, which is basically a strike slip fault, capable of generating an earthquake of Mw 6.7. Thus it is evident that the proposed Bridge needs to be designed considering the adverse geo-hydrological condition as well as the earthquake aspects needing special attention following the state-of-the-art technology as guided by relevant codes and published literatures. Considering the soil profile of these locations ground response analysis has been carried out using equivalent linear method to determine the site amplification. Site specific response spectra have been developed for the four zones and zone factors have been determined. The computed zone factors are 0.198g, 0.195g, 0.195g and 0.20g for the four zones respectively, much higher than the zone factor 0.16g, which is for zone III, as stipulated in IS 1893:2002."

Jan 1, 2015

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 Filippo Maria Leoni, George Filz, Wesley Schmutzler, Matteo Bertoni

"The US Army Corps of Engineers selected the Deep Mixing Method (DMM) for the required stabilization at the LPV 111 Project (New Orleans, USA). DMM was used for ground improvement/foundation strengthening and consequently to stabilize and support the burden of the new levee. Two different technologies were used: Trevi Turbo Mix (TTM) and Contrivance Innovation Cement Mixing Columns (CI-CMC). LPV 111 is the largest soil mixing project to date in the USA with its more than 18,000 elements installed to a depth of up to 67 feet for a total of 1.7 million cubic yards of treated soil. The preparation and execution of the project presented many challenges from various points of view. The little time available to complete the job led to the simultaneous utilization of eight deep mixing rigs and batch plants which worked 24 hours per day, 5.5 days per week on a stretch of land approximately 5.3 miles long. Given the imposing geographical extent of the project, a four phase laboratory programme and five field validation test programmes, conducted in as many different areas of the project, were completed to design and optimize the grout mixes and the installation parameters. The massive quality control/quality assurance testing programme produced over 500 drilled core holes and over 5,000 tested specimens in order to determine unconfined compressive strength (UCS) and uniformity of the DMM elements. This paper has the purposes of describing the tremendous challenges encountered and providing valuableinformation that may be useful for other future projects, including details not previously published.INTRODUCTIONReach LPV-111 is part of the Lake Pontchartrain and Vicinity Hurricane Protection System designed to protect the city of New Orleans and the surrounding areas from the surge that would accompany a 100 year hurricane event. LPV-111 measures approximately 8.5 km (5.3 miles) long, of which 7.2 (4.5 miles) extend along the north bank of the Gulf Intracoastal Waterway (GIWW) and the remaining 1.3 (0.8 miles) run north and terminates at the CSX Railroad Gate. The Bayou Sauvage National Wildlife Refuge borders the levee on both sides (Fig. 1)."

Jan 1, 2015

By Monique Nykamp

"INTRODUCTIONTerminal 46 is located just south of downtown Seattle, and is one of the Port of Seattle’s busiest container terminals. The Terminal 46 Redevelopment Project was undertaken to replace the existing 15-m-wide (50 ft) cranes along the apron with 30-m-wide (100 ft) cranes, which can unload larger, post- Panamax ships. The project included upgrading the existing waterside crane rail with new piles and constructing a new land-side rail behind the sheetpile bulkhead. The new piles had to be installed adjacent to the existing apron without causing damage, which was a signifi cant geotechnical challenge due to the soft soil conditions at the site. An instrumentation program performed during the test pile program evaluated this challenge and allowed for the development of specifi c production pile installation procedures that had the least possible effect on construction costs and schedule. SITE HISTORYThe site lies along the west side of Elliott Bay, north of the mouth of the Duwamish Waterway. Prior to development, this area was part of the tide fl ats where the Duwamish River drained into Elliott Bay. Prior to 1970, there were several existing timber piers and structures in the area. In the 1970s, the Port of Seattle constructed a 900-m-long (3,000 ft), 30- m-wide (100 ft) apron to support fi ve, 15-m-wide (50 ft) container cranes. The contained backland area was then fi lled with dredged spoils (sand and silt with organics) and the upper 5 to 20 m (16 to 65 ft) backfi lled with sand and gravel.The existing apron was constructed using 0.4 m (16 in) octagonal prestressed concrete piles to support the precast concrete deck and crane rails. The pile-supported bents were spaced at 6.1 m (20 ft), center-to-center, along the longitudinal direction. Pile lengths typically varied from about 20 to 40 m (65 to 130 ft) with 15 to 26 m penetration below mudline (50 to 85 ft penetration). The slope below the apron was constructed at about 1.75 horizontal to 1 vertical to allow for suffi cient water depth for cargo ships. In most areas, a riprap buttress was placed at the toe of the slope. A typical cross section of the apron is shown on Figure 2.Several stability, settlement and pile driving issues arose during the original construction of T-46 (Pita, 1983). Reportedly, movement of the submarine slope occurred during pile driving, resulting in settlement behind the bulkhead. Pile driving reportedly caused settlement of adjacent piles. In addition, some piles were “running” (dropping quickly under one hammer blow) during installation."

Jan 1, 2007

By Monique Nykamp

"INTRODUCTIONTerminal 46 is located just south of downtown Seattle, and is one of the Port of Seattle’s busiest container terminals. The Terminal 46 Redevelopment Project was undertaken to replace the existing 15-m-wide (50 ft) cranes along the apron with 30-m-wide (100 ft) cranes, which can unload larger, post- Panamax ships. The project included upgrading the existing waterside crane rail with new piles and constructing a new land-side rail behind the sheetpile bulkhead. The new piles had to be installed adjacent to the existing apron without causing damage, which was a signifi cant geotechnical challenge due to the soft soil conditions at the site. An instrumentation program performed during the test pile program evaluated this challenge and allowed for the development of specifi c production pile installation procedures that had the least possible effect on construction costs and schedule.SITE HISTORYThe site lies along the west side of Elliott Bay, north of the mouth of the Duwamish Waterway. Prior to development, this area was part of the tide fl ats where the Duwamish River drained into Elliott Bay. Prior to 1970, there were several existing timber piers and structures in the area. In the 1970s, the Port of Seattle constructed a 900-m-long (3,000 ft), 30- m-wide (100 ft) apron to support fi ve, 15-m-wide (50 ft) container cranes. The contained backland area was then fi lled with dredged spoils (sand and silt with organics) and the upper 5 to 20 m (16 to 65 ft) backfi lled with sand and gravel.The existing apron was constructed using 0.4 m (16 in) octagonal prestressed concrete piles to support the precast concrete deck and crane rails. The pile-supported bents were spaced at 6.1 m (20 ft), center-to-center, along the longitudinal direction. Pile lengths typically varied from about 20 to 40 m (65 to 130 ft) with 15 to 26 m penetration below mudline (50 to 85 ft penetration). The slope below the apron was constructed at about 1.75 horizontal to 1 vertical to allow for suffi cient water depth for cargo ships. In most areas, a riprap buttress was placed at the toe of the slope. A typical cross section of the apron is shown on Figure 2.Several stability, settlement and pile driving issues arose during the original construction of T-46 (Pita, 1983). Reportedly, movement of the submarine slope occurred during pile driving, resulting in settlement behind the bulkhead. Pile driving reportedly caused settlement of adjacent piles. In addition, some piles were “running” (dropping quickly under one hammer blow) during installation."

Jan 1, 2007

By Ricardo Dobry, Alain Pecker, George E. Leventis, Ralph B. Peck

"This year’s DFI Outstanding Project Award is for the design and construction of the foundation scheme for the largest cable-stayed bridge in the world. In 1993, Gefyra, SA (a French/Greek consortium led by VINCI of Paris, France) was awarded a €750 million ($1billion+ USD) Concession Contract to design, build, fi nance, operate and maintain a three-span cable-stayed suspension bridge connecting the Peloponnese, Greece’s southernmost peninsula, with the mainland across the Gulf of Corinth. The contract extends over a 42-year period, 7 years for design and construction and 35 years for operation. The project was fi nanced through a combination of public funds, private equity and bank loans. Alternative foundation concepts that were considered included traditional driven piles, deeply embedded caissons and soil improvement. PROJECT CHALLENGESThe extreme technical challenges faced included:??Weak foundation soils composed of soft alluvial deposits consisting of interbedded layers of granular and cohesive materials with thin layers and lenses of gravel and liquefi able sand pockets; rock is believed to be at a depth of 1,000 m (3,500 ft) or more.??A very deep seabed exceeding 60 m (200 ft).??The requirement to withstand the collision of 180,000-ton tankers traveling at 16 knots.??Maximum wind forces of 250 km/hour (155 mi/hour).??Design seismic forces corresponding to Richter magnitudes of 7.0+ with peak ground accelerations of 0.48 g at seabed.??Design tectonic movements of 2 m (7 ft) in any direction between any two adjacent bridge pier foundations/pylons.Considering subsurface conditions and local seismicity and water depths, foundation design and construction methods were the key drivers for this project. In large part, the success of the project is owed to the unprecedented partnering and collaboration between all partners involved fostered under the leadership of Jean Paul Teyssandier and Gilles De Maublanc of VINCI Group (France) who served as lead Concessionaire and General Contractor. The joint venture’s lead Greek partners were Elliniki Technodomiki/AKTOR and J&P/AVAX. Alain Pecker of Geodynamique et Structure (France) served as lead Geotechnical Consultant/ Designer while Buckland and Taylor (Canada) served as Design Checkers with Ralph Peck and Ricardo Dobry (U.S.) as Special Advisors on foundation issues, Langan International/Langan Engineering and Environmental Services P.C. (George E. Leventis, Gregory Biesiadecki and Diane Fiorelli) served as Technical Advisor on geotechnical, geodynamic and foundation/marine construction issues."

Jan 1, 2007

By Andrew Z. Boeckelmann, David S. Graham, Paul J. Axtell

In the last fifteen years, several research studies have evaluated the ability to detect various types of deep foundation concrete integrity flaws with crosshole sonic logging (CSL) and thermal integrity profiling (TIP). This paper synthesizes the findings from the research, focusing on two studies that included CSL and TIP testing of drilled shafts with various types of flaws. The first, a 2016 research study of test shafts for the Wisconsin DOT, included inclusions inside and outside the reinforcing cage, intentional tremie withdrawal during concreting, and soft bottom flaws. The second, a 2021 study of production shafts for the Missouri DOT, included one shaft with and another without soft bottom conditions. After synthesizing the ability of each test method to detect each type of flaw, the paper presents recommendations for improving how CSL and TIP results are evaluated in practice. The recommendations highlight DFI‟s CSL interpretation protocol as well as the importance of evaluating TIP data versus time, not just depth. The paper includes example temperature-versus-time plots for various types of flaws and emphasizes how temperature-versus-time evaluation can be used to distinguish soft bottom conditions from standard bottom-of-shaft temperature roll off.

Oct 1, 2022

By Suthan Pooranampillai

Verification of drilled shaft resistance is primarily obtained through the use of different load testing methods. Procedures utilized include conventional top down static loading, the Osterberg load cell (O-cell) test and dynamic tests such as the Statnamic method. The O-cell test provides a means of obtaining separately the base and side shear resistance behavior of drilled shafts (cast-in-drilled-hole). Alternatively, the Statnamic load test method enables the engineer to derive base and side shear behavior separately, based on measurements of load, accelerations and strains along the length of the shaft. However, due to time and cost constraints these tests can only be performed on selected shafts within a project. Post grouting of a drilled shaft base embedded within a cohesionless material, with a low mobility compaction grout, will essentially pre-load the shaft base soil against the side shear and self-weight in much the same manner as an O-cell load test (when the load cell is placed within the base vicinity). Therefore, successful post grouting of a drilled shaft would enable verification of both shaft side shear and base resistance simultaneously on each and every shaft it is carried out on. Additionally, such post grouted shafts display stiffer load-displacement response during subsequent downward, superstructure induced, loading compared to ungrouted shafts. Verification of resistance on each and every shaft through the use of post grouting will allow an increase in resistance factors (reduction in safety factor) used in the design. Two 6 ft. diameter drilled shafts were constructed in Fredonia, WA, for WSDOT, each with an approximate length of 52 ft. The shafts were terminated within medium dense poorly graded silty sand. Statnamic load testing of the shafts indicated maximum derived static side shear and base resistances of 2545 kips and 507 kips (1.6 in. displacement) for shaft One and 2466 kips and 212 kips (1.4 in. displacement) for shaft Two. Shaft Two was subsequently grouted, with a low mobility compaction grout. Shaft base mounted total earth pressure cells measured a maximum sustained pressure of 55.44 ksf during the compaction grouting operation. Shaft displacement reached 0.65 inches in the upward direction at termination of grouting. Comparison of grouting data with initial load test information indicates that properly instrumented post grouting verifies shaft base and side shear resistance. In addition, these grouting induced resistances were much higher than design values supplied by the engineer using conventional resistance factor design. Large scale laboratory testing also shows that base grouting verifies higher soil resistances than permissible in conventional design.

Jan 1, 2010

By Chunli Wei, Mark Jen, Xiaojun Wang

"After more than 85 years of service, a critical link between New York and New Jersey, the Goethals Bridge over the Arthur Kill waterway, is being replaced with two new parallel bridges. Each bridge includes 1,650 feet long signature steel composite cable-stayed bridge, a 2,789 feet long New York approach and a 1,889 feet long New Jersey approach. The superstructure of each approach is supported on a series of two-column concrete piers and each column is supported on a single large diameter drilled shaft varying from 4.5 to 9 feet in diameter and anchored 45 feet below ground into the underlying rock.A performance-based methodology was followed for the strength and extreme event limit states design of the drilled shaft foundations. The design for seismic loads has been performed using the AASHTO Guide Specifications for LRFD Seismic Bridge Design. For all strength and service loads, the AASHTO LRFD Bridge Design Specifications were used. Since the longitudinal and confinement requirements in the two specifications vary, the minimum longitudinal reinforcement was based on the more stringent requirements of the two codes. A design example is presented to illustrate the methodology in bridge deep foundation design using nonlinear time-history global analysis results with soil-pile interaction represented by sets of horizontal and vertical nonlinear soil springs along the drilled shaft, based on the soil and rock properties from the boreholes test results. In this paper the design methodology implements strain limits related to earthquake intensities and damage levels to calculate the capacity using XTRACT analysis, which aids designers to adopt applicable provisions that meet specific design requirements.INTRODUCTIONAfter more than 85 years of service, a critical link between New York and New Jersey, the Goethals Bridge over the Arthur Kill waterway, is being replaced with two new parallel bridges designed to carry vehicular traffic and a future mass transit corridor. They include two 1,650 feet long signature steel composite cablestayed bridges with 260 feet tall V-shaped concrete gateway towers (Figure 1). The approaches consist of continuous pre-stressed concrete girders. The New York approach is a single structure consisting of 18 continuous spans, sloping at 4% for a total length of 2,789 feet without expansion joints. Similarly, the longest continuous portion on the New Jersey approach, with a similar slope, consists of 11 spans for a total length of 1,889 feet without expansion joints. The superstructure of each approach is supported on a series of two-column concrete piers that vary in height from 121.3 feet near the cable-stayed bridges to 11.8 feet near the abutments. Each column is supported on a single large diameter drilled shaft varying from 4.5 to 9 feet in diameter and anchored 45 feet below ground into the underlying rock."

Jan 1, 2016

By Alex Grenoble, Alex Reeb, George Filz, Farzad Abedzadeh

"This paper summarizes available information on the characteristics and properties of deep-mixed soilcement produced by the wet method. The topics covered in this paper include: unit weight, unconfined compressive strength, strength variability for field mixed materials, influence of curing time, influence of consolidation pressure, Young’s modulus, differences in strength and stiffness between small and large samples, creep deformations, Poisson’s ratio, and tensile strength. In addition, this paper discusses the development of design considerations and recommended property values for a project that uses soilcement to protect an existing dam penstock from loads applied by an overlying stability berm. Some of the key recommendations for the deep-mixed soil-cement to be used in this project are that (1) a curved strength envelope that includes tensile strength can be used in the analysis, (2) the stress-strain and strength properties can be characterized using Duncan and Chang's (1970) hyperbolic model, and (3) a specification based on the median unconfined compressive strength value is appropriate.INTRODUCTIONFor many projects, including foundation and embankment support, deep mixing can be designed based on simplified procedures and following standardized guidelines (e.g., FHWA 2013). However for unusually complex or critical projects, it is often necessary to perform numerical analyses, and in order to perform these numerical analyses well, a thorough understanding of the material properties is needed.This paper summarizes information on the characteristics and properties of deep-mixed soil-cement produced by the wet method, and it discusses the development of design considerations and recommended property values for a specific project, herein referred to as the penstock project, that requires numerical analyses. For the penstock project, a horseshoe-shaped enclosure of soil-cement is being considered beside and above an existing dam penstock to protect it from loads applied by an overlying stability berm that will be constructed for seismic remediation. The concept is to use soilcement created by the deep mixing method along the sides of the penstock and to use compacted soilcement above the deep mixing to create the crown of the protective soil-cement zone around the penstock. For this application, the soil-cement stiffness, rather than its strength, is the controlling design parameter. To achieve the necessary soil-cement stiffness, the strength will be high enough that the factor-of-safety values against instability along potential failure surfaces passing through the soil-cement are high. Following conventional practice, the soil-cement acceptance criteria will be based on the unconfined compressive strength, and the specified strength will be selected to produce the desired modulus value."

Jan 1, 2015

By Mohamed A. Eliwah

This paper deals with the determination of hydraulic conductivity of the coastal coralline limestone aquifer of Jeddah, Saudi Arabia. This coastal area has witnessed urban development and establishment of towers which requires deep foundations, excavation and dewatering of huge quantities of unconfined groundwater. It is occupied with successive layers of soft detrital and consolidated massive cavernous coralline limestone of the Quaternary age. These layers are encountered at a depth of 1.5m and extend for more than 100m. Hydraulic conductivity values were obtained by analyzing the pumping tests data under steady and transient state conditions. Hydraulic conductivity values help in selecting the proper and safe dewatering system, as well as determination of discharge rates and quantities of groundwater to be withdrawn. Test results obtained from two surveyed sites showed that the values of hydraulic conductivity are greatly variable. It ranges between 118.1 and 1559.6 m/day at the first site, whereas at the second one it ranges between 94.6 and 350 m/day. These high values are attributed to the cavernous nature of the water-bearing formation. Jeddah city could be divided into three different dewatering zones extending from north to south parallel to the coast line. Well point dewatering system could be applied in the first zone while ditches and sumps are the most suitable dewatering method in the second and third zones. Dewatering using deep wells in such highly permeable formation will require withdrawal of huge quantities of water which will be accompanied by washing out fine sediment filling the cavities in the surrounding areas. This will badly affect the nearby buildings through settlement, crakes and other structural damages. Therefore, construction of grouting plug/blanket with thickness of 3.0 m at a depth of 20.0 m is recommended. This depth will be enough to support the plug against the hydrostatic pressure. Moreover, it is highly recommended to transfer the site into closed box, by using diaphragm walls or secant bored piles.

By Mario Mauro, Jeff Taylor, Carlos Morales

"In 2007 the US Army Corps of Engineers classified the Herbert Hoover Dike in Florida as a Dam Safety Action Classification (DSAC) 1 dam, and started the implementation of one of the largest dam rehabilitation projects in the nation. The construction of the cutoff wall is a key feature of this rehabilitation work to upgrade the dike to current dam safety criteria. The cutoff wall installation is currently being completed on Reach 1, which extends from Port Mayaca to Belle Glade, under a Multiple Task Order Contract based on performance specifications and stringent verification criteria.For the construction of the cutoff wall TREVIICOS selected the self-hardening slurry method. Since the cutoff wall is installed through a layer of highly variable limestone with Unconfined Compressive Strength (UCS) up to 14,000 psi, the excavation requires the use of the hydromill equipment. This is the first successful application of the hydromill technology with self-hardening slurry in a large scale project in the US. This paper presents the details of the method utilized, the quality control procedures, and the experience gained over seven miles of cutoff wall installed.INTRODUCTIONProject LocationThe Herbert Hoover Dike (HHD) system, around Lake Okeechobee in South Florida, consists of a series of levees, culverts and locks and is approximately 143 miles long (Figure 1).Lake Okeechobee is the second largest freshwater lake in the lower 48 states of the United States. The lake is the primary drinking water source for numerous communities around the lake and to millions of people living along the lower east coast. The lake is also a vital source of irrigation for the agricultural industry in the South Florida region.Lake Okeechobee is 33 miles wide from north to south and 30 miles wide from east to west and has a surface area of 730 square miles. The average water depth of the lake is 9 ft."

Jan 1, 2017

By Terence Ma, Seok hyeon Chai, Jeff Lam, Thamer Yacoub, Brigid Cami, Sina Javankhoshdel

The Limit Equilibrium (LE) analysis of pile-supported geotechnical structures normally assumes a constant shear force for the pile instead of considering the non-linear capacity of the pile which is related to the pile displacement. In this study, a 3D Limit Equilibrium analysis is carried out for a landslide model supported with piles by considering the constant and non-linear capacity of the pile which is computed using a separate Finite Element (FE) algorithm. The depth of the pile, soil layering, and the pile properties are used with an assumed maximum displacement to compute the geotechnical non-linear capacity of the pile. In this study, the results of the initial unreinforced 3D LE model was first compared to the 3D FE analysis results. Then, the pile pattern was applied to the failure region in the 3D LE model, and then the factor of safety was recomputed. The results of the constant shear piles were compared to the model with the non-linear piles.

Sep 8, 2021

By Abhirami B., V. Balakumar

Piled raft foundation system is an intelligent geotechnical concept, developed towards reducing the settlement of the raft and the footings by providing pile elements below the raft or footings, as the case maybe. Although a large volume of works has been done on the behaviour of piled rafts by observational studies, the effect of construction methodologies such as deep excavations, the installation methodologies used for piling etc appear to have not been covered adequately. This paper discusses the effect of deep excavations, pile installation techniques and the effect of adding structural elements, based on the data available from published literatures. Based on this study, the performance of the piled raft monitored by the author has been revisited and the results of such a study are discussed.

Nov 1, 2022

By Paul J. Sabatini

Between 2008 and 2009, more than 6,000, 23-m long deep mixing method (DMM) elements were constructed to support 124 concrete mats comprising the foundations for the process trains for an LNG facility. The Owner requested first-of-its-kind analyses and assessments to confirm the quality and reliability of the DMM foundation. This paper provides information on these assessments and the procedures used to ultimately conclude that a fit-for-purpose foundation system was constructed. During early phases of construction, several DMM test cores revealed nodules of unmixed clay in upper core samples. A comprehensive review of available DMM core information was undertaken. It was concluded that the amount of coring being conducted as part of the contractor?s QA/QC program should be increased to achieve a foundation system with the required level of reliability. Three-dimensional finite element analyses were completed considering various distributions of defects in the DMM elements and the effects of potential downdrag on DMM elements. Calculated mat settlements and mat stresses were compared to cases without defects in the DMM elements. Various distributions of loaded and unloaded mat areas and number and position (both in the subsurface and laterally) of defects were considered. Four (of the 124) mats were identified as potentially ?at-risk?. The settlement performance of these mats is currently being monitored and, to date, performance has been acceptable.

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

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

Jan 1, 2016

By David W. Martel, Tom George

"As part of the regional water authority review and upgrade of local dams a 35m x 5m x 3m wet soil mixed block was required for stabilisation of a dam wall toe in remote Victoria, Australia. Remote access, extremely poor roads and high mobilisation costs made more traditional CSM and deep mixing methods cost prohibitive. The dam required a redesign to raise the wall by 2.0m to increase water storage. Additionally, the dam required additional stabilisation to reduce the risk of liquefaction during an earthquake event. Soil testing indicated loose, cohesionless, high permeability soils to a depth of 3.0 to 3.5m across the toe of the wall. This resulted in high dam seepage through the toe of dam wall potentially causing the factor of safety during a seismic event to decrease to a dangerous level. A number of laboratory trials were completed to determine the mix ratio of cement required to improve the strength of the saturated, liquefiable soil.Wagstaff Piling was responsible for achieving the required soil/cement strength and mix depth on site. As the ground conditions were too soft for conventional soil mixing equipment, an excavator mounted Mitsui road header was modified to fit a 20 tonne excavator. A purpose built remote batching plant was set up on more stable ground approximately 200m from the wall and utilised for preparation of cement and water slurry for supply to the machine. As the ground was too soft to support the excavator, the progressively improved ground was used as the working platform. Both wet grab sampling and in situ testing was undertaken to determine the UCS of the improved soil. These results indicated several variations in the results due to size effects.1 INTRODUCTIONA small town in remote Victoria relies totally on its water supply from a small dam. The dam wall required stabilisation works by ground improvement as studies completed on the dam classified it as a high risk of failure under an earthquake event. In addition, the earth fill dam had high levels of seepage and poor control measures, requiring the dam to be upgraded to comply with all regulations.The relevant water authority engaged a contractor under a design and construct contract to complete the works. Wagstaff Piling was engaged as the Subcontractor to provide design and construction advice including the contract for the ground improvement works. Initial discussions involved CSM walls, cut-off walls and mass soil mixing solutions. However, due to the access restrictions for piling equipment, mass soiling mixing was the chosen method of ground improvement."

Jan 1, 2015

By Bruno Vingiani, Alessandro Bertero

"The use of Artificial Ground Freezing (AGF) for temporary soil strengthening and seepage control is an effective alternative to grouting when dealing with soils whose degree of finesses would imply the use of highly expensive chemical grouts. However, compared to grouting, the application of this improvement technique usually needs a more accurate preliminary soil investigation campaign and a design assisted by specific calculation software. Besides a general description of the main features of this technique, the paper will describe a recent application of AGF carried out in Rome to underpass an existing metro station.INTRODUCTIONNatural ground freezing occurs seasonally or permanently (permafrost) in some areas of the globe close to the poles and can negatively affect the engineering performance of underground structures. On the other hand, Artificial Ground Freezing (AGF) is man-made controllable freezing process that can be used in foundation engineering to temporarily strengthen the ground and create a barrier to the passage of groundwater. During the process, the heat is extracted from the soil in a cylindrical shape around a number of freezing pipes installed into the ground. This action produces columns of frozen soil, which expand gradually till they merge and create continuous frozen wall. The thickness of this barrier can be regulated according to the specific project requirements. Nowadays, AGF technique is applied to a wide range of foundation engineering problems where soil stability and groundwater flows are an issue (Pimentel et al. 2011, Haß and Schäfers, 2013). Typical applications include the temporary stabilization and waterproof of the ground around the excavation profile of mined tunnels until the construction of the final lining (Figure 1).The case history described in this paper deals with a recent application of AGF carried out during the construction of metro Line “C” in Rome. Specifically, this technique has been applied to allow the construction of two single-track mined tunnels running underneath an existing metro station belonging to Line “A”. In that case, the AGF has been evaluated by the Designers as the only possible solution for improving the mechanical and hydraulic characteristics"

Jan 1, 1900

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 Benjamin Jennings, Jason Herron

In the summer of 2016 Xcel Energy experienced a storm event that resulted in the collapse of approximately 8.5 miles of a 345 KV transmission line near Rogers, Minnesota. In design of the new transmission line, Xcel Energy determined that ten tower locations would be replaced with steel H-frame structures supported by helical piles instead of wood H-frame structures supported by driven wooden piles. A steel foundation was proposed for the towers due to time constraints and site conditions unfavorable to large pile driving equipment. Xcel Energy contacted the helical pile manufacturer Hubbell Power Systems, Inc. (HPS) for aid in the design of a complete steel foundation for the structure legs. With the shear, moment, and axial loads provided, the manufacturer used pile group modeling and axial capacity software to design a four helical pile group; and used 3D modeling and finite element software to design a moment resistant grillage to connect to the tower base. The steel grillage utilizes a new moment resistant connection and clamp system to transfer loads from the piles to the grillage. This connection provides a true fixed head condition and reduces lateral deflection issues typical to smaller diameter piles in pinned head connections. The clamp is designed to deform the helical pipe pile shaft and transfer the full axial load of the structure through the mechanical and friction connection. The helical piles and the moment resistant grillage were manufactured with shorter than average lead times and a helical pile installation contractor performed the installation. An expedient plan of install was developed by the contractor that resulted in an average installation rate of one complete set of tower foundations per day. The design of the moment resistant grillage, clamping system, and excellent foundation construction by the contractor provided an expedient and efficient foundation system to be discussed in this paper.

Jan 1, 2017