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By Bernardo J. Jiménez Vega, Edy L. T. Montalvan

Rammed stone columns and similar reinforcement systems are used worldwide more frequently as a cost-effective method for improvement of foundations on soft soils. The effectiveness of the treatment method is evidenced by the increase in bearing capacity and reduction of compressibility of the treated ground. In this study, two job sites with over 500 stone columns were studied. On both jobs sites, shallow soft silty soils were found and stone columns were designed to support the foundations of MSE walls, which serve as abutments for viaducts. In order to verify the soil improvement efficiency CPT tests were performed before and after the construction of stone columns, also plate load tests were performed on both job sites to verify the deformation modulus of the stone columns. From CPT data it was observed an increase up to 30% of sleeve friction and 20% of tip resistance, which demonstrated a higher deformation modulus maintaining the same strength in the soil after stone columns construction. The plate load tests yield load-deformation curves which indicated that the original assumed modulus was conservative. As a result of these findings, optimization of the settlement reduction ratios was conducted using the modified values of deformation modulus for the soil and stone column, obtaining a reduction up to 30% of stone columns for further job sites with similar soil conditions.

Sep 8, 2021

By Lee S. Vanzler

Atlantic Wharf involved the construction of a six-level underground parking garage and a 32-story high rise tower along the historic Boston Harbor waterfront. The site, historically known as ?Russia Wharf,? consisted of filled land initially created in the late 1800s by extending the shoreline toward the harbor as the urban population and land needs grew to support expansion of commerce and trade. Redevelopment required solutions to address relics of waterfront structures (granite block seawalls, piles, and piers), weak subsurface soil conditions, tidal groundwater levels, and contaminated soils resulting from previous site usage and filling. The foundation system, consisting of drilled shafts with column loads up to 14,000 kips (62,272 kN), concrete diaphragm wall (slurry wall), and up-down construction methodology, was chosen to address these factors. As a prerequisite for development, selected portions of the façades of the former historic buildings were required to be preserved, protected, and incorporated into the final building configuration. The historic façades were temporarily braced and supported prior to the demolition of the buildings and commencement of below-grade construction. This paper will describe the considerations in the selection of up-down construction methodology along with a discussion of the design and performance of the concrete diaphragm wall and drilled shaft foundations. Up-down construction methodology shortened the overall construction schedule while addressing the lateral bracing requirements for the concrete diaphragm wall and restrictive ground movement tolerances to protect adjacent structures. Below-grade construction was completed in March 2010, and the building was opened for tenant occupancy in January 2011.

Jan 1, 2011

By Julie H. N. Hampden, Per G. Reinhall

"Executive summary: Impact pile driving of steel piles is a common construction practice in freshwater and marine environments for the building of structures and foundations. This practice produces extremely high sound levels underwater that have proven injurious to aquatic fish and wildlife. To limit impacts to sensitive species, resource management agencies employ a variety of different strategies including timing restrictions to limit in-water construction windows to those months when there are low flow conditions in lakes or rivers, to those hours when tides are low, or to periods of the year when species of concern are least likely to be present in the project vicinity. In addition, permitting agencies have identified noise thresholds above which sensitive species could be injured, resulting in additional project conditions to curtail the extent of project noise impacts including: limiting the number of piles or pile strikes per day, requiring biological monitoring, and mandating the use of noise attenuation techniques, such as bubble curtains and cofferdams. Numerous studies have shown current noise attenuation techniques are costly and provide limited or variable noise reduction [1-3]. This is because the noise from pile driving is not only transmitted through the water column, it is also transmitted through the sediment back into the water column [1, 4-8]. Though these protective measures may help to reduce project impacts, they also result in additional complexity, expense, and potential risk for project delivery. Marine Construction Technologies, a Public Benefit Corporation, in collaboration with University of Washington and Washington State Department of Transportation, has developed a pile that can be installed with standard pile driving technologies (vibratory or impact hammers) and consistently decreases the total noise transmitted into the water. The double-walled pile is relatively quiet in comparison to unattenuated piles or existing noise attenuation techniques. This technology not only reduces the risk to sensitive species by minimizing the extent of potential impacts, it also reduces potential risks to project delivery by limiting the size of monitoring areas, minimizing the need to cap daily production rates, and eliminating the need for deployment of additional noise attenuation devices. Results from finite element modeling of the pile, scaled prototype testing, and full scale field testing in Commencement Bay (October 2014) and Vashon Island (October 2015) in Puget Sound, Washington indicate a reduction the peak sound pressure between 14 and 20 dB relative to single walled piles at a range of approximately 10 meters. These tests also confirm that the double-walled piles provide drivability similar to standard steel piles. In addition, preliminary calculations for capacity and structural characteristics demonstrate that double-walled piles provide equivalent or better performance than same-sized standard piles."

Jan 1, 2017

By James W. Niehoff

"Prior to 2003, most high rise structures in Honolulu, Hawaii were supported on driven pile foundations, extending through shallow coral strata and bearing in competent formations at depths of 100 ft (30 m) or greater. In 2003, the 40-story Hokua Tower became the first building in Hawaii to use continuous flight auger (CFA) piles for support. These piles derived most of their capacity from side shear in the shallow coral formations, which reduced their required lengths to less than 100 ft (30 m) sand significantly increased their capacity. Not only did CFA piles prove to be more efficient and cost-effective than driven piles, but the reduced noise and vibration associated with their installation made them and drilled piers the foundations of choice for most mid- to high-rise projects going forward. Because drilled foundations were new to Hawaii, it was necessary to develop effective design parameters for the unique soil and rock conditions found within this urban area. While drilled foundations were found to have many advantages over driven piles, construction techniques had to be modified to compensate for extensive voids in the coral formations. This paper presents a compendium of the data derived from numerous full scale, instrumented load tests conducted during the past decade and provides guidance for the design and installation of CFA and drilled pier foundation systems in areas having geologic settings and history similar to that of Honolulu.INTRODUCTIONThe State of Hawaii is one of the most remote areas in the world, lying nearly 2400 miles (3800 km) from the nearest continental land mass. In spite of this vast distance, the population of the islands has grown to over 1 million people, the majority of whom live within and in close proximity to the City of Honolulu on the Island of Oahu. The city is densely populated with over 400 high rise apartments, condominiums, hotels and office buildings located within 5 miles (8 km) of the city center (Fig.1). Nearly all of these buildings have been constructed within the past 50 years."

Jan 1, 2016

By R. Gerritsen, Erwin de Jong, E. van der Velde, C. te Boekhorst

"In recent years the market for Mixed-In-Place soil mix techniques in the Netherlands has been growing rapidly. Initially the technique was used to create cut-off walls near river dikes and as a vibration free method to create retaining walls for building pits. Studies have been undertaken and projects are executed in order to strengthen the dike itself by the use of Mixed-In-Place techniques. In February 2012 Bauer Funderingstechniek started the construction of the first polder in the Netherlands with their approved Mixed-In-Place cut-off walls. This article explains the background of the use of this cost-effective and durable construction method and discusses how the challenging requirements from the client were fulfilled, both in design and execution. The quality assurance and quality control consisted of preliminary soil and mixture investigations, extensive measurements during construction and leakage detection through geophysical methods. The information is presented in 3 case histories, all subprojects of a large infrastructural project ‘Leeuwarden Vrij-Baan’ in the Netherlands.INTRODUCTIONThe Netherlands have a worldwide reputation in creating their own country by reclaiming land from the sea. Since the 15th century the Dutch have been creating “polders”, areas of reclaimed land below sea level, surrounded by dykes and with a mechanically maintained water level. In the 20th century the use of artificial polders became an interesting construction method for creating underpasses below motorways and canals using watertight geomembranes to create an impermeable layer that separated the polder from its surroundings. These kinds of structures have one big disadvantage, they need a lot of space. The main idea of such a structure is that the upward water pressure under the geomembrane has to be in balance with the remaining soil on top of it. For this reason, the geomembrane has to be placed at a depth significantly deeper than the polder surface, depending on the hydraulic head in the aquifer. Slopes of 1:3 (1 vertical : 3 horizontal) are most commonly used, resulting in very large open excavations and massive earthworks, even for relatively small underpasses. Special measures can be taken to reduce the spatial use with vertical limits, but these measures will increase the building costs (Gerritsen et al. 2014)."

Jan 1, 2015

By Paolo Cavalcoli, Federico Pagliacci, Marco Chiarabelli

"The Sheikh Jaber Al-Ahmad Causeway Project in Kuwait is estimated at approximately $US3.7 billion and consists of constructing a causeway across the Kuwait Bay, connecting the Shuwaikh Port with the northern Subiyah area, where the new “Silk City” will be established. The $US77 billion Silk City will revive the ancient “Silk Road” trade route and will become a major free trade zone linking central Asia with Europe. The new city will be completed in 2030, it will house about 700,000 people and, furthermore, it will include the tallest tower in the world. The Causeway will stretch approximately 23.3 miles and will be composed of a combination of low-level bridges, embankments and transition islands. A bridge of about 16.8 miles in length will span the navigation channel and a free flow interchange at the Shuwaikh Port will connect the causeway to the main road network in Kuwait City. The geo-construction portion of the project involves the execution of 1,200 drilled shafts with diameters of 98 inches and 118 inches embedded to a maximum depth of about 276 feet. Details are provided concerning the subsurface conditions, the geotechnical characteristics and the strength parameters, illustrating, as well, the installation technique implemented for the construction of the drilled shafts. In addition, particular attention is paid to the description of the challenges faced while constructing the drilled shafts at a distance of about 10 miles from the shore, such as the depth of the water above the midline (more than 160 feet), an underwater current and the tidal variation.INTRODUCTIONThis paper presents an overview of the foundation works executed for a 37km causeway across the Bay of Kuwait, connecting Shuwaikh Port with Subiyah New Town Development. The project, in which Trevi is actively engaged, includes a 27 km low-level bridge across the bay, a main bridge with a span of 200 m, an overpass and a 5 km approach road onshore in Subiyah.The main purpose of this report is to provide information about the nature and features of the applied technique of bored piles, including a description of each work phase and other related details, in order to aid in the design of the foundations for the proposed construction.Works for the soil investigation were carried out in accordance with accepted geotechnical standards/guidelines. Brief descriptions of the methodology of the field are also provided in this report."

Jan 1, 2016

By Takeshi Maki, Kh. Adeel Tariq

"The lateral resistance of the structure plays an important role during seismic event and it can be increased by using ground improvement. In this study an attempt has been made to investigate the effect of cement-treated sand on the lateral capacity of the pile. The behavior of piles surrounded by sand only and cement-treated sand confined in a steel box (30 x 30 x 50 cm) which is subjected to lateral cyclic load has been investigated. Piles having a diameter of 2.5 cm and embedded to a depth of 45 cm were used. Steel and aluminum piles were used to investigate the effect of flexural stiffness on the lateral capacity of the pile. Bottom supports of piles were also changed from pinned to fix. Well graded sand compacted to 70% of relative density (RD) was used. Cement-treated sand having a compressive strength of 3.7 MPa was used. Displacement controled lateral load tests were performed and cyclic loads were applied until pile displacement was 4%, 10%, 20%, 35%, 50%, 75% and 100% of pile diameter. Results evaluated are compared with common method of analysis like Brinch hansen (1961), Brom (1964), Poluos (1980) etc. Results have indicated that the stiffness of a pile affects its lateral capacity. The introduction of central cement-treated sand part increased 5 times the lateral capacity of piles as compared with a sand only condition.IntroductionPiles are used extensively around the world to support loads of structures. Piles are commonly used to carry axial load, but in some structures, the lateral capacity of the pile is more important than the axial capacity: for example piles supporting earth retaining structures, electric tower foundation, etc. Structures can be subjected to both axial and lateral forces, like structures constructed at harbor that are subjected to lateral force due to waves action; and structures built in earthquake prone areas like Japan."

Jan 1, 2017

By Helen S. W. Chow, Harry G. Poulos

Most modern buildings involve the construction of a basement, often of several levels, to maximize the floor area ratio. The basement walls are generally designed for excavation retention purposes only, and are infrequently considered as elements which can help to support the structural loads from the superstructure. However, the basement walls can provide substantial stiffness and resistance to structural loads, and may contribute to the overall foundation capacity and stiffness. This paper presents a simplified approach to approximate the overall foundation capacity and stiffness considering the various components of the foundation system, including the foundation piles, the basement floor slab, the basement walls and interaction between each foundation component. The effect of the basement walls in enhancing the foundation stiffness values is examined by reference to the results of finite element analyses which consider a foundation subjected to vertical, horizontal and moment loadings. The approximate approach is found to give results that are adequate for a preliminary assessment of the effects of basement walls on the overall foundation response, without the need for detailed three-dimensional finite element analyses.

Nov 1, 2022

By Scott A. Walker, Gabriel J. Alcantar, Brian Zuckerman, Ramin Golesorkhi

"The stadium development consists of construction of a 68,500-seat, open-air NFL football stadium for the San Francisco 49ers. The main structure will consist of a 7-story above grade steel structure supported by over 3,000 piles. Berkel and Company Contractors, Inc. (Berkel) was selected as the design-build pile contractor who used their auger pressure grouted displacement (APGD) piles for this project. During an indicator pile installation and pile load test program, fifteen piles were tested to develop installation criteria to support demands of 150kips tension and 180 kips compression. Following the indicator pile program Berkel installed 3088 piles in 30 working days. Throughout pile installation data were collected with an automated data acquisition system (DAS). During pile installation field engineers from Treadwell & Rollo observed the pile installation as well as the real-time data from the DAS. Strategic staging and pre-production planning by Berkel along with consistent collaboration with the design team created an atmosphere for a successful and on schedule project completion.IntroductionThe new San Francisco 49ers Stadium in Santa Clara, California will be a 68,500-seat facility, a rendering of which is shown in Figure 1. The main structure will consist of a 7-story above grade steel structure supported by more than 3,000 piles. The north, east and south portions of the stadium are designed as an open seating bowl, while the western portion includes open seating at the lower levels and seven-story tower which houses over 150 suites.The stadium project includes the stadium structure, as well as elevated open pedestrian walkways, commercial community space, and three new pedestrian bridges spanning a nearby by creek. Sustainable designs and innovations such as a green roof, photovoltaic panels, a ground source geothermal system, stadium-wide Wi-Fi capability, and access to public transit are provided throughout the project. The stadium is designed as an open, light, and airy structure and is surrounded by an existing amusement park, office buildings, the Santa Clara Convention Center, and the training facility of the 49ers."

Jan 1, 2015

By Waddah Akili

At an offshore site along the Red Sea coast of Saudi Arabia, marine structures were supported on tubular steel piles driven into coral and coral contaminated sands and silts. Surprises and disappointments faced during the installation of the piled foundation were, to a large measure, due to inappropriate design methodology and absence of proper soil information. The paper describes the design evolution process, highlights the static pile test program conducted to verify design parameters, and amplifies the need to prepare for worst possible scenario when coral deposits are encountered. Despite corrections made to the design, based on site-specific insitu parameters (skin friction, end bearing) perceived from load tests conducted on site; the final design adopted overestimated capacities in over 50 percent of total piles driven. The paper describes the changes introduced to the design during the execution of the project, highlights the pile test program conducted to verify the design, and compares pile design penetration with actual penetration depth. The unpredictable and erratic pile behavior observed, ascertains the need for more appropriate pile design and installation guidelines for driven piles in coral and coral contaminated formations.

By Krishnendu Mandal

"For a multi-story building project in Kolkata, a pile load testing program was conducted to minimize pile performance uncertainty resulting from variable subsurface conditions and to verify the pile load vs. settlement response. The program consisted of performing five (5) instrumented load tests on augured cast-in-place (ACIP) pre-production test piles. Vibrating-wire strain gages and extensometers were installed in the test piles at strategic locations to enable measurements of the load vs. deformation behavior of the test piles. This paper presents a description of site subsurface conditions, test pile installation, instrumentation setup for a maintained load test (MLT), static compression pile load test results, and pile instrumentation result interpretation. Average mobilized unit shaft resistance values are calculated.2.0 INTRODUCTIONThe project site is located in Kolkata, near river Ganges, and the proposed development plans consist of constructing six (6)25-story (G+25) towers; see Fig. 1 and Fig. 2 below for approximate site location and proposed development layout, respectively. The buildings were designed to be supported on ACIP piles. A field load test program was implemented to verify sub-surface conditions and pile design. The test program consisted of installing Five (5) instrumented test piles numbered LP1A and B through LP6A and B, and performing static compression load tests on these piles. The piles were instrumented with vibrating-wire strain gauges and extensometers, so that the pile shaft resistance distribution along pile length and the pile toe resistance could be interpreted using direct instrumentation measurements."

Jan 1, 2015

By Michael Arnold

"BAUER Foundation Corp. was one of three contractors awarded with the installation of a cut-off wall at the Herbert Hoover Dike Rehabilitation project. The cut-off wall was constructed up to 84 feet deep and 25 inches thick. It extended from the crest through the middle of the existing dike into the underlying peat, sand, and rock layers. BAUER used the cement deep soil mixing method of Cutter Soil Mixing (CSM) to install the wall. Soil mixing was facilitated by first removing the peat layer in the wall alignment using Kelly drilling and replacing it with suitable backfill, resulting in a secant pile wall arrangement of replacement columns. BAUER successfully finished four task orders with a total length of just over 10 miles. Up to six rigs of the types BAUER BG 28, BAUER BG 40 and RTG RG 25 were concurrently used to perform the replacement columns and the cut-off wall installation.The paper introduces the project, the geotechnical site conditions, and the requirements specified by USACE. It focuses on the specific adaptation of the CSM method to the site conditions and on the equipment used. Strength and permeability results obtained from an extensive testing program are presented. The impact of the curing conditions on lab and in-situ test results is studied, and test results are related to soil conditions.PROJECTThe Herbert Hoover Dike is a 143-mile-long dike encircling Lake Okeechobee in south central Florida. When it was constructed in the 1930s and 1960s, the purpose of Herbert Hoover Dike was flood protection from hurricanes. However, during the 1970s a higher lake level was maintained permanently to provide local agriculture with water. Later, damage became apparent during two nearly back-to-back high water events in the 1990s, when numerous sink holes, seeps, pipes, and boils were observed (Fig. 1). In 2000, the Congress approved USACE to propose rehabilitation measures. The installation of a cut-off wall into the existing dike was chosen during the initial design process as the preferred measure to improve the safety of the dike (Davis et al. 2009).The first section of the dike to be rehabilitated was Reach 1 located along the southeast side of the lake between the towns of Port Mayaca and Belle Glade. An indefinite delivery indefinite quantity (IDIQ) multiple award task order contract (MATOC) was issued for this 22.4-mile-long stretch by USACE in 2007. BAUER Foundation Corp. (BAUER) was one of the three contractors that succeeded in the qualification process. Each of the three successful contractors had their own novel construction techniques. In the years 2008 to 2012 BAUER executed four task orders totaling over 10.0 lineal miles of cut-off wall with 3.3 million square feet of design surface area."

Jan 1, 2015

By J. Gniel, L. King, C. Gaudin, C. O’Loughlin

"This paper presents some recent advancements in centrifuge modelling, which enable the installation of displacement piles to be performed in-flight while measuring ground responses. Details and results are provided from a series of experiments where 21 full-displacement piles were installed into a sample of consolidated kaolin clay at 40g. The piles were pushed into the sample at a constant rate of penetration, with installation reaction loads and pore pressures measured. Insight into the installation effects of the full-displacement piles was obtained by undertaking in-situ testing pre- and postinstallation of piles. The findings show that centrifuge testing has the potential to play an important role in furthering the current understanding of displacement pile behaviour and installation effects.INTRODUCTIONDisplacement piles and displacement ground improvement columns cause soil to undergo significant distortion and shearing during installation, which alters the soil properties. It is essential to consider these changes in soil properties to estimate the behaviour of pile foundations with higher degree of accuracy. However, the installation effects of displacement piles are widely considered as one of the most difficult geotechnical mechanisms to model, both analytically and numerically, and experimental data is needed to advance the current state of knowledge.Theories, analytical and semi-analytical, have been developed to describe the displacement pile installation process. Randolph et al. (1979) applied the cylindrical Cavity Expansion Method (CEM) to model the installation of a displacement pile in a fine grained cohesive soil. However, cylindrical CEM only considers the field variables in radial coordinates, and hence the soil-pile interface can only be modelled as a frictionless material. Baligh (1985) introduced the Strain Path Method (SPM), which assumes soil flows around the tip of a displacement pile. SPM was shown to model the stress and strain fields, particularly within close proximity to the pile, more accurately compared to the cylindrical CEM. While these methods account for the installation effects of a displacement pile and can be used to estimate a resulting ultimate bearing capacity, they are unable to describe the load-settlement behaviour of such piles. With the added complexity of group effects, existing analytical methods do not provide a means to accurately calculate the ground response to the installation of a group of displacement piles in a cohesive soil.The advancement of computational power, numerical techniques and constitutive models has improved the accuracy of numerical analysis, particularly in regard to modelling pile installation. However, even with advanced techniques, Finite Element Method (FEM) suffers a number of disadvantages due to the large deformations, which results in mesh distortion and tangling. Mesh-free methods such as Discrete Element Method (DEM), Smoothed Particle Hydrodynamics (SPH) and Material Point Method (MPM) are the next generation of computational techniques that are able to deal with large deformation problems. However, these advanced techniques are computationally expensive, complex and yet to be incorporated into commercial packages. Such methods are considered to still be in the development stage and are yet to provide a complete solution to pile installation problems."

Jan 1, 1900

By Andrew Budek

"Analytical and experimental work has shown that achieving the full inelastic lateral capacity of a pile may require the formation of a plastic hinge below ground level, in the pile shaft. The confining action of soil about the pile shaft was further been shown to greatly enhance the ductility capacity of the pile. An experimental program was therefore undertaken to build in the effect of external confinement through the addition of a GFRP jacket to the subgrade plastic hinge region. Two piles were thus modified, and compared to an unjacketed pile in a test rig which simulated a subgrade moment pattern and soil confinement. The ductility achieved by the jacketed piles was found to be substantially lower than an unjacketed control specimen. Failure mode of the jacketed specimens was also undesirable, involving complete tendon rupture and sudden loss in capacity IntroductionSeismic loading of concrete pile shafts can result in a demand for inelastic response. In the case of a superstructure supported by a single pile (i.e., a pile-column forming a single-column bridge pier, in which there is no rotational restraint at the top of the pile}, a plastic hinge will form below grade, at a depth which varies with soil properties and above-grade height of the center of seismic mass.In the case of a superstructure supported by multiple piles, there is rotational restraint, and the connection will experience inelastic action first. However, development of the full lateral inelastic capacity of the pile may call for the formation of a second, subgrade plastic hinge (fig. 1 )."

Jan 1, 2005

By Marwa Nabil, Alaa A. Ata

"Recent developments in the analysis of piled rafts has incorporated the load sharing of the raft and the piles to support the superstructure. In the piled-raft system, piles are cast monolithically with the raft and the load is partly transmitted by the raft to the soil directly below it, and partly by the piles to more competent deep soil. While these piles are effective in increasing the bearing capacity and reducing the settlements, they often lead to significant straining actions at the pile head-raft connection which may constitute the weakest link. An attempt to provide a more economical solution, that at the same time overcomes this weak link, is to disconnect the pile heads from the raft and introduce an intermediate cushion of compacted fill. In this case, the piles are considered as reinforcement to the subsoil and will also act as settlement reducers. This paper investigates the load transfers mechanism of the unconnected piled raft with cushion using ABAQUS finite elements Program. The main objective is to provide an in depth analysis of the raft–soil–pile interactions in multi-layered soil under static and seismic loads. The investigated system provides an economical alternative for traditional connected piled raft foundation, where there is no need to reinforce the piles, no need for pile head demolition or expensive waterproofing of the pile head connection. Cost analyses of unconnected versus connected piled raft systems confirmed a cost savings in the construction that may reach from 50 to 70 percent.INTRODUCTIONDesigners around the world have gained more confidence to use the piled-raft as a more realistic system where the raft and the piles share transferring the superstructure loads to shallow and deep soil layers. A further advancement is to use unconnected piled rafts as another practical and economical alternative to the traditional piled rafts. Unconnected piled raft is also synonymous to settlement reducing piles; or simply, soil improvement piles. Liang et al. (2003) has extended the concept of pile-raft-foundation to a new type of foundation called composite piled raft foundation or unconnected piled raft foundation. The foundation is composed of a sand/gravel cushion sandwiched between the raft and piles. The piles group may contain short and long piles. The short piles are constructed of flexible materials such as soil-cement columns or sand-gravel columns, and are used mainly to improve the bearing capacity of shallow soft soil; the long piles, which are made of relatively rigid materials such as concrete, and their main function is to reduce settlements. The cushion plays an important role in mobilizing the bearing capacity of the subsoil and in modifying the load transfer mechanism of the piles. In Shanghai, China, this system of unconnected piled raft has proved to be quite suitable and effective in coastal areas, where deep soft soil deposits exist."

Jan 1, 2016

By Clifford Taylor, Alexander Zöhrer

"The execution of deep basement excavations under narrow conditions is one of the most challenging tasks in geotechnics. The vicinity of neighbouring buildings, roads, and underground structures such as sewers or power lines, quite often prohibits the application of standard solutions. In addition, legal considerations in the use of adjacent properties is becoming increasingly difficult. This paper will present some innovative approaches to overcome the above-mentioned challenges based on several case studies from central Europe. For every project the design approach as well as the techniques used for execution will be explained, detailing both the advantages and the limitations of the applications. One case study shows a deep basement excavation (approx. 17m) in the centre of Prague, Czech Republic. This project featured many challenging boundary conditions (narrow construction area, high ground water table, jet grouting column embedment into bedrock, constraints regarding use of ground anchors due to property rights, etc). The realisation of the complex design is described and illustrated in detail. Other case studies will show the combined application of bored piles with jet grouting and also explain the design of vertical prestressed anchors for retaining walls.INTRODUCTIONThe development of urban areas has always presented challenges, from access for equipment and materials to the rectification of existing foundations in unknown condition. Compounding these is the increasingly stringent requirements to retain, maintain and reduce impact on culturally and historically significant structures. As available space is becoming more limited, optimisation of real estate has resulted in buildings getting higher and their basements deeper below ground. Two or more basement levels are quite common, with typical excavation depths ranging from 5 to more than 10m. Additionally, we are faced with neighbouring buildings that are equally high, deep and massive. These buildings directly adjacent the retaining structure require underpinning to limit settlement, and in cases where they are within just a few meters, this building mass generates additional earth pressure for the retaining wall to support, resulting in complex loading cases.This paper highlights several common challenges and explores the measures implemented to overcome them. The challenges and examples of either design based solutions or practical applications will focus on the following topics – the limitations of conventional geotechnical construction methods, overcoming challenging geology and the requirement for watertight basement constructions."

Jan 1, 1900

By Hayel M. El-Naggar, Mohamed Sobhi, Mamdouh M. Hamza, Marawan M. Shahien

"This paper presents the results of two lateral load tests on large bored piles in soft clay deposit for a major site in northern Egypt. The tests are carried out on 0.8 m diameter piles. One of the tests is carried out on the pile where the clay starts from the ground surface. The other test is carried out on a pile after surface improvement by replacing the top 1.50 m of the clay deposit by compacted granular soil. The results of the tests show the influence of the surface replacement layer on the lateral load versus lateral displacement relationships of the loaded pile. The results of the two tests are used to calibrate a 3D Finite Element Analysis model for the pile. The model is used to investigate the influence of the thickness and lateral extent of the surface replacement layer on the behavior of laterally loaded large bored piles.INTRODUCTIONLateral loads for piles are produced by seismic events, wind, wave action, ship impact, traffic, and land slide forces. The lateral resistance of a pile is controlled by the stiffness and the strength of the material of the pile and the soil surrounding the upper portion of the pile. In most situations, the soil surrounding the upper portion of the pile is too weak to sustain the design lateral loads. Thus there is a need to increase the lateral resistance of the pile or groups of piles. Such an increase may be achieved by either increase number of piles or increase pile diameter. Alternatively, an economic way to increase the lateral resistance is to improve the soil surrounding the upper portion of the pile (Rollins and Brown, 2011; Faro et al., 2015).Ground improvement has the ability to increase the lateral resistance of the pile by increasing the passive resistance of the soil surrounding the upper portion of the pile. The ground improvement techniques have the potential for being more cost-effective and reducing construction time. In spite of this fact, such techniques are rarely implemented in practice. Further, there are relatively few tests or records available in the literature to guide engineers in evaluating the actual effectiveness of this approach. In addition, there is no standard or methodology to aid engineers in designing increase of lateral resistance with surface ground improvement. There are specific improvement methods for each soil type, whether it is loose cohesionless soil or soft cohesive soil and these methods are provided by Michell (1981), Tershai and Juran (2000), ASCE (1997), and Rollins and Brown (2011). Furthermore, there are number of case histories that add a new hole in the sight, such as the cases provided by Brown et al. (1987, 1988), Mokwa and Duncan (2001), Rollins et al. (2005), Rollins and Cole (2006), Cole and Rollins (2006), Rollins, Snyder et al. (2010) , Rollins, Gerber, and Kwon (2010), Rollins and Nasr (2010), and Gerber et al. (2010)."

Jan 1, 2016

By Venkatesh S. V J, Shubha M, Srilakshmi G

Choosing for the best option of pile foundations to overcome large lateral and uplift loads for the foundations in transmission line towers/offshore environment is still being a concern to achieve the required capacities but also by considering the suitability aspect in the environment. The objective of this paper is to review the methods that have been done for knowing the uplift resistance and lateral resistance of pedestal piles. Investigations by different methods such as experimental studies, numerical and analytical studies have been done by various researchers in order to evaluate the response of a belled pile. These methods are discussed in this paper and the comparison with straight shaft pile based upon the test and analysis. The results indicated that the uplift resistance and lateral resistance were significantly increased with the adoption of belled piles than straight shaft piles.

Sep 1, 2022

By C. Guney Olgun, Mohammad Khosravi, Daniel W. Wilson, Deepak Rayamajhi, Scott A. Ashford, Shuji Tamura, Ross W. Boulanger

"Dynamic centrifuge tests were performed on unimproved and improved soil with soil-cement column models. The reinforcing effect of isolated soil-cement columns for reducing liquefaction potential and ground deformation in improved soil were investigated. This paper presents the observed acceleration, pore pressure, and settlement responses under an earthquake base motion for both unimproved and improved soil models. In addition, lateral reinforcing effects of soil-cement columns were also investigated in terms of site stiffening effects and the increasing natural frequency of improved soil. The test results show that the soil-cement columns were rather ineffective in preventing liquefaction triggering in improved soil and in significantly reducing the magnitude of the resulting soil settlement compared to the model with unimproved soil profile. Furthermore, the predicted natural frequency of the improved soil profile estimated using existing design equations is shown to be significantly higher than the observed natural frequency inferred from centrifuge tests results. These design equations assume shear strain compatibility between the columns and the surrounding soil. On the other hand, revised design equations that account for shear strain incompatibility between column and surrounding soil are shown to give reasonable estimates compared to the observed natural frequency of the improved soil model.INTRODUCTIONGround improvement using stiff columns (e.g., stone columns, deep-soil-mixing columns, and jet-grout columns), are often used in practice to reduce liquefaction potential (and associated deformations) in loose soil sites. Typically, saturated silty soils are difficult to densify or drain rapidly due to their lower hydraulic conductivity, so densification and drainage techniques of improvement are often found to be ineffective. Instead, the shear reinforcing mechanisms of stiff columns are considered effective for reducing the seismic stresses and strains, and thereby reducing liquefaction potential in the enclosed saturated silty soils (Baez 1995, Adalier and Elgamal 2004, Mitchell 2008)."

Jan 1, 2015

By Ramanathan Ayothiraman, Anurag Singh

"An experimental program was undertaken to investigate the effects of randomly distributed basalt fibre on the index and engineering properties of Dhanori clay and to compare its performance with the properties of soil reinforced with polypropylene fibre. In the present investigation, 7 groups of soil samples were prepared at four different percentages of basalt fibre and polypropylene fibre content and tests were done for measuring their consistency limits, compaction characteristics, unconfined compression strength and consolidation properties. The test results indicate that the inclusion of basalt fibre in Dhanori clay resulted in significant improvement in properties. The improved properties are not comparable with polypropylene fibres, nevertheless, the improvement by basalt fibres is able to meet the typical design target values and the cost is very much less than synthetic fibres. More importantly, basalt fibres are environment friendly.INTRODUCTIONConstruction of buildings in low lands with engineered filling, flexible and rigid pavements for highways/airfields, and embankments for highways/railways are also part of major infrastructural development in addition to construction of tall buildings, bridges/fly overs, major dams and underground structures. The later projects require different improvement techniques than that is adopted in the former projects. Ground improvement techniques such as use of reinforcement inclusions within soil found as an effective and reliable technique. Especially such modification by fibre reinforcement, is primarily possible in engineered filling, pavements subgrade and embankments, where surface mixing is easier; and may not be feasible when stabilization/modification is required for deeper depths. In comparison with conventional reinforcement using geosynthetics (strips, geotextile, geogrid, etc.), there are some advantages in using randomly distributed fibre as reinforcement. In past few decades, the discrete fibres are simply added and mixed randomly with soil, in much the same way as cement, lime, or other additives.There are several studies (Ziegler et al. 1998; Puppala et al. 2000; Bei-xing et al. 2004; Cai et al. 2006; Tang et al. 2007, 2012, 2016; Abdi et al. 2008; Viswanadham et al. 2009; Le et al. 2015) that investigated the behaviour of polypropylene fibre-reinforced soil and reported that an increase in fibre content caused an increase in strength and shrinkage potential but brought on the reduction of swelling potential. The length of fibres had an insignificant effect on soil characteristics, whereas fibre contents proved more influential and effective. A study on rubber fibre conducted by Hambirao and Rakaraddi (2014) mentions that tensile cracking of clays can be improved with the inclusion of short rubber fibres, optimum fibre content was about 15 % of weight of soil. Several experimental studies (Babu et al. 2008; Chaple and Dhatrak 2013; Vibhakar and Nahta 2014; Soundara and Senthilkumar 2015; Goyal et al. 2015; Jayasree et al. 2014, 2015) were conducted on coir fibre-reinforced soil and concluded that it helped in reducing the swell potential and 1% fibre by weight of the soil almost doubled the CBR value. Martins et al. (2015) found that 4% of sisal fibre by weight of the soil reduced the visibility of cracks. Pillai and Ayothiraman (2012), Ayothiraman et al. (2014) and Sahu et al. (2016) have demonstrated that human hair fibres can be used to improve the properties of both fine grained and coarse grained soils."

Jan 1, 1900