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By Jeffrey M. Taylor, Arturo Ressi di Cervia

"Construction of the drilled shafts for the Brightman Street Bridge Replacement Project were not only challenging due to working over the water but were also challenged by changed soil conditions, concurrent work being performed by an adjacent contractor on the same project, environmental restrictions and severe winter conditions. A total of 36 x 8 foot (2.44m) diameter drilled shafts with 7.5 foot (2.31m) rock sockets were installed for the East and West bascule piers. This project also included Osterberg Cell load testing on two production drilled shafts at both the East and West bascule piers. The results from the load test program were used to fine tune the design of the drilled shaft rock sockets. From a constructability standpoint the reverse circulation drilling method with a pile top drill rig proved to be an excellent choice for drilling the overburden and rock sockets of the large diameter deep drilled shafts. INTRODUCTIONThe replacement Brightman Street Bridge spans the Taunton River between Fall River and Somerset in Massachusetts.The new crossing is located approximately 1500 feet (450m) upstream from the existing Brightman Street Bridge, which was built in 1908. The new mainline bridge includes nine spans totaling 1725 feet (525m). A bascule type moveable span will be located in the middle of the Taunton River and provide a 200 foot (61m) open channel centered about the 400 foot (122m) navigational channel. The bascule span, which has a span length of 409 feet (124.7m), will be a trunnion-type four leaf structure with a solid deck. A site plan is shown in Figure 1 Contract 3, which includes construction of the foundations for the East and West bascule piers, was bid on December 19, 2000 and was awarded to Modern Continental Construction Company (MCC) on January 24, 2001. MCC in turn awarded the subcontract for the installation of the drilled shafts to TREVIICOS Corporation, which started mobilizing in June of 2001.The scope of work for the drilled shafts of Contract 3 consisted in installing 18 drilled shafts in three rows on each side of the river to support the bascule piers located in the middle of the Taunton River.The foundation plan for the bascule span is shown in Figure 2."

Jan 1, 2004

By K Ilamparuthi, R. K. Madhumathi

"This paper presents the results of 1g model tests conducted on model piles both single and two pile groups embedded in sand by physically inducing lateral soil movement. From the test results it was found that the pile with higher L/D ratio exhibits higher deflection in case of pile embedded in medium dense sand whereas in loose sand the response is vice versa with higher deflection for the pile of lesser L/D ratio. The induced bending moment in piles is more for longer piles than shorter piles irrespective of the density of sand bed. It is also found that the pile head deflection and the bending moment are found to decrease exponentially with increasing distance between the pile and the wall. For pile group arranged in a row parallel and perpendicular to retaining wall, the deflection of single pile is more than the deflection of two pile group irrespective of the depth of excavation for spacing of piles tested. The influence of soil movement on the lateral response of pile is also analyzed through 3-dimensional finite element analysis. The numerical results thus obtained are validated with the results of experiments. The Mohr-Coulomb material model adopted to represent the soil behaviour predicts the response of pile reasonably and compares well with the experimentally observed response.INTRODUCTIONPile foundations are adopted to support structures such as foundations of high rise buildings, transmission towers, offshore platforms, bridge abutments etc., when good bearing stratum is not present at shallow depth to bear the loads of these structures. In the recent past particularly in the urbanized areas structures are built close to one another and nearby excavation will cause a reduction of lateral earth pressure and soil movement behind the retaining wall (Ong, 2004). The reduction in support stress will induce additional movement to the pile and leading to distress in pile foundations located adjacent to supported excavation. In these situations understanding the response of piles next to supported excavations becomes essential.The behavior of piles subjected to soil movement was studied by Poulos and Chen (1996 and1997) through tests on 1g models and the findings concluded that the maximum bending moment was found to decrease with decreasing pile diameter and decreasing pile spacing . Leung et al. (2000 and 2003) studied the effects of excavation induced soil movement on pile foundations in sand through centrifuge tests and established that the restraints on the pile head would cause additional shear force and/or bending moment at the pile head, although the restraints help to reduce the pile head deflection/rotation. In the theoretical studies of Poulos & Chen (1997), boundary element method (PALLAS) was used for analysing the pile subjected to lateral soil movement and charts were proposed for designing the piles. Pan et al. (2002) and Miao et al. (2006) analysed the passive pile behavior through three dimensional finite element analyses. However research works reported on piles subjected to lateral soil movement are limited."

Jan 1, 2015

By Brandon M. Robinson, Osman F. Besler, Dominik Gaechter

With the increase in population over the last decade, and anticipated population growth over the coming years, Norway is making significant investments in the Country’s infrastructure. Part of this investment in development starts with the Intercity development project in South-East Norway, which is the largest transport project in Norway. The Intercity Development project consists of 270 km (167 mi.) of new doubletrack rail, capable of train speeds reaching 250 km/h (155 mph). The new stations are centrally located in the major cities, in South-East Norway, to provide the benefit to as many citizens as possible. The goal of the project is to reduce the increase in traffic, which is coupled with an increase in population, and reduce the travel times between the cities. The Intercity Development Project has an anticipated completion date of 2034. The Sandbukta-Moss-Såstad (SMS) project, part of the Intercity development, includes 10 km (6.2 mi) of new double-track railway and is situated on the Østfold Line, near the city of Moss, Norway shown in Fig. 1. The 10 km SMS-section covers three open stretches and two tunnels, including 630 m (2,066 ft) substructure for double-track railways on the open line at Sandbukta. The Moss tunnel is a 1720 m (5,643 ft) long tunnel from Sandbukta to Moss center, including a 420 m (1,378 ft) long concrete culvert. The new Moss station includes an 800 m (2,625 ft) long station area. The Carlberg tunnel is a 2350 m (7,710 ft) long tunnel from Kleberget to Carlberg, including a 200 m (656 ft) long concrete culvert.

Sep 8, 2021

By Racquel Nottingham, Marc Mastrantuono

Micropiles often provide a favourable solution for many deep foundation problems especially when significant site constraints such as confined construction sites or vibration limitations have been identified. Often the durability of buried steel elements are heavily scrutinized in order to effectively determine the rates of corrosion and methods to reduce this while still maintaining the structural integrity of the engineered solution. Practices such as sacrificial corrosion loss and the introduction of plastic sheaths have become the go-to methods of corrosion protection. Since the introduction of the micropile, other solutions have been developed, namely protection with an adequate grout encapsulation. This paper will explore corrosion protection of micropiles and the guidelines provided in the published codes and norms. Since few codes define the exact way to verify the durability of these micropiled structures, the existing data is presented and the analysis of grout encapsulation as an effective corrosion protection method is evaluated.

Oct 1, 2022

By Susan Rafalko, Mike Walker, John Sankey, Sherif Aziz, Alex Potter-Weight, Mary Nodine, Frederic Masse

"After several successful projects on the Garden State Parkway and New Jersey Turnpike for support of single-stage MSE (Mechanically Stabilized Earth) walls using rigid inclusions (Controlled Modulus Columns) as an alternate to two-stage MSE walls and surcharge, the Bass River Bridge Widening project presented additional challenges in terms of soil conditions and height of embankment that created opportunities for the design-build ground improvement contractor and its MSE wall-designing partner to enhance their design and construction methods. The specialist contractor decided, in association with the wall system supplier, to perform an independent large scale instrumented test area on the project to demonstrate the ability of the design techniques to model the behavior of the system, as well as the capacity of the rigid inclusions to provide the necessary bearing capacity and settlement control to allow the construction of the highway without any consolidation period. This paper presents a detailed description of the design of the ground improvement system and MSE wall system, as well as the results and conclusions of the monitoring data gathered on the large scale test program. The combination of rigid inclusion ground improvement technologies, such as the CMC system, together with an MSE wall system allows for the rapid and economical construction of high embankment without waiting for a surcharge and consolidation period or the necessity to use a two-stage wall system. In-depth understanding of the design techniques and advantages of this combination will be provided and should be beneficial for any geotechnical engineer or owner looking for innovative solutions to save both time and cost on their projects.1. IntroductionAs development continues on sites with poor ground conditions throughout the world, conventional MSE walls remain a flexible design solution; however, construction of MSE walls in combination with ground improvement is becoming more frequent where extreme differential and/or total settlement prevail due to soft ground conditions. Various techniques have been used in the past in such conditions (e.g. conventional surcharge, staged construction, or two-stage MSE walls), even though these design solutions have typically involved longer waiting times for settlement to occur. As a result, conventional MSE wall design has been combined with a variety of ground improvement techniques consisting of rigid inclusions for an economical and efficient solution with the potential to accelerate construction and limit long term settlement. For the particular subject of this paper, the specialist contractor (Menard) proposed to use CMCs (Controlled Modulus Columns) to support the highest part of the MSE wall. CMCs are grouted displacement rigid inclusions installed in a grid-like pattern using a displacement auger. Before the CMCs are installed, a working platform may first need to be placed to allow equipment to move around the site depending on the ground conditions. Following the CMC ground improvement, an LTP (Load Transfer Platform) is installed prior to the construction of the MSE wall."

Jan 1, 2015

By Mahdi Soudkhah, Akhter Hossain

Vertical micropiles are generally considered to be low in lateral resistance. Therefore, battered micropiles are often used when additional lateral load carrying capacity is required. However, battering of micropiles can sometimes be restricted due to existing adjacent structures or utilities, especially in highly urbanized areas. For example, presented in this paper are lateral load test data from a 43-story building project in New York City where vertical micropiles were used due to proximity to adjacent structures. Three static lateral load tests were conducted on micropiles consisting of 13.375-in-outside diameter and 25- to 51-ft-long casings, and socketed 10 to 12.6 ft into the bedrock (gneissic schist). The subsurface profile above the bedrock consists of loose to very dense, mostly sandy and silty soils. The design load for the three test piles was 14,000 lb and the maximum load applied during the tests was 200% of the design load. Lateral load- displacement behavior of the free pile heads from the load tests are compared with the results of p-y analyses based on a widely used p-y method for sandy soils and using a lower and an upper bound estimates of soil index properties and strength parameters. Since the existing p-y curves were formulated for larger diameter driven piles at a specific geographic location, major differences are observed between the results of the load tests and the p-y analyses. In general, the lateral displacements estimated based on the p-y analyses using upper bound soil parameters are relatively closer to the results of the field load testing. Modified p-y curves specific to the sandy and silty soils representative of the general subsurface conditions of New York City matched with the lateral load tests are presented in this paper. INTRODUCTION Micropiles generally are limited in lateral load carrying capacities due to their relatively higher slenderness ratios (ratio of depth to diameter) compared to more conventional deep foundation alternatives, such as driven piles and drilled shafts. So, micropiles are not typically considered as deep foundation solutions when significantly high lateral loads are expected on the substructures. Various means to increase the lateral resistance of micropiles include battering and installing an oversized casing in the top portion of the piles (FHWA 2005; and Richard and Rothbauer 2004). However, it is often not possible to install micropiles in a battered position in highly urbanized areas due to existing adjacent structures or utilities. Installation of oversized casing is often restricted by limited space availability and concerns of losing lateral capacities due to closely spaced group of piles. Thus, estimation of lateral resistance of vertical micropiles can become highly important for geotechnical engineering projects in urban areas when a small to moderate amount of lateral resistances are expected from the substructures, often to withstand seismic and wind loads.

Jan 1, 2019

By Thomas D. Humbert, Christopher J. Ramsey

Construction of a new underground parking structure in State College, Pennsylvania, is situated on a site constrained by limited ROW and required excavations ranging in depth from 25 ft to 40 ft. Additional complications included busy surface streets, an active intersection, and numerous underground utilities that could not be disrupted by construction activities. To combat these challenges, an innovative approach for earth retention was designed that combined multiple types of retention systems. The overall system included alternating sections of soil nail walls and a hybrid system of soldier pile walls (consisting of micropiles) that were partially restrained by a soil nail wall in the lower portions of the excavation. Further, due to the limited space within the property limits that inhibited the length of the permanent nails, the wall design team collaborated with the project designers to develop a solution such that the completed wall became an integral part of the final design/construction of the underground parking structure. INTRODUCTION HERE at State College is a mixed-use, high-rise building in State College, Pennsylvania. The 12-strory building has up to 3 levels of below-grade parking, with the above-grade levels consisting of residential and commercial/retail space. The existing property was a parking lot bound by the streets Calder Way to the north, Garner Street to the east, East Beaver Avenue to the south, and Heister Street to the west. The overall property sloped approximately 20 ft in elevation from southeast to northwest. Excavation for the below-grade levels extended 21 ft to 36 ft (6.4 m to 11 m) below street level. During design-development phases of the project, it became evident that due to subsurface conditions and right-of- way limitations, conventional construction techniques would not be feasible. The full perimeter of the excavation would require earth retention including the weak shale bedrock along the bottom of the excavation. The project developer (CA Ventures) and general contractor (Brinkmann) coordinated with the specialty contractor and wall design engineer to find a solution. At this time, Coastal Drilling East (specialty contractor) and Wood Environment & Infrastructure Solutions (wall design engineer) became involved. The project developer and general contractor were aware they needed an earth retention system, but given the many variables the project faced, a single, straightforward solution would not work in this application.

Jan 1, 2019

By Garland Likins, Gray Mullins, George Piscsalko

"Quality control of drilled shafts is greatly dependent upon the practices of the site personnel. For drilled shafts cast under slurry, inspection of the hole prior to concreting is very difficult or impossible. There are numerous non-destructive test (NDT) methods currently available to assess the integrity of drilled shafts. This paper will discuss the theory and use of an emerging NDT technology known as Thermal Integrity Profiling (TIP). The Thermal Integrity Profiling method measures the elevated concrete temperatures that occur during the hydration process. These temperature measurements are made along the length of the pile and can determine the integrity over 100% of the pile cross section, both inside and outside the reinforcing cage. With the known shaft volume information, TIP can evaluate the effective shaft radius at each measurement location. With the increased use of TIP on highway projects, there is a need to have standard criteria for shaft acceptance. Shaft acceptance criteria can be based upon thermal measurements and subsequent analysis of the data to determine the average shaft radius, local concrete cover, and cage alignment. With this additional information obtained via the thermal testing method, acceptance methods based upon concrete cover can be developed. In this paper the Thermal Integrity Profiling method will be described, results from a case history will be discussed, and an acceptance criteria based upon concrete cover will be proposed.INTRODUCTIONDrilled shafts are an attractive foundation element in many applications due to their large axial and lateral capacities. When drilled shafts are cast in a dry hole, it is possible to inspect the hole prior to casting, allowing for very basic level of quality control, although the shape of the completed element is still unknown without some form of post construction testing. When drilled shafts are installed where soil conditions are unstable, the shafts will often be cast under slurry to support the surrounding soils during the construction process. When casting a drilled shaft under slurry, it is very difficult to impossible to accurately and efficiently inspect the hole prior to casting concrete and it is equally difficult or impossible to inspect the shaft during the casting process"

Jan 1, 2016

By Jeffrey C. Evans, Daniel G. Ruffing, Hejintao Huang

Soil-bentonite slurry trench cutoff walls are the most common type of vertical cutoff wall used in the US for seepage control and for passive control of contaminant migration at environmental sites. Design considerations are often limited to constructability considerations and a target hydraulic conductivity. With design-build contracts common, the backfill design is often left to the contractor. As a barrier soil, the hydraulic conductivity of bentonite slurry wall backfill is typically required to be equal to or below 1x10-7cm/s. The importance of stress state upon the hydraulic conductivity as well as the expected stresses are both established in the literature. Grain size distribution of the base soil and bentonite content both affect compressibility and hydraulic conductivity. This paper describes the results of studies undertaken to evaluate the interrelationships between compressibility, hydraulic conductivity, grain size distribution, and bentonite content. Three base soils were used representing a range of soils found on typical construction projects. Using these base soils, mixtures containing a range of dry bentonite contents from 0% to 5% were prepared to a slump consistent with field practice. The compressibility and hydraulic conductivity were measured in consolidometers adapted for falling head permeability tests at the end of each load increment. These experiments yielded the relationship between effective stress and hydraulic conductivity as well as consolidation characteristics including time rate of consolidation and coefficients of compressibility. The experimental results are then used to indirectly evaluate stress development and to assess the time needed for consolidation. The findings show a substantial decrease in hydraulic conductivity as effective stress increases, regardless of base soil type and dry bentonite content, a relative insensitivity of stress development to backfill compressibility, and a wide range of values for coefficient of consolidation depending upon backfill mixture and stress level.

Jan 1, 2016

By Armin W. Stuedlein, Jim Zammataro, Bernie Hertlein, Daniel Belardo, Qiang Li, Antonio Marinucci

"An experimental program focusing on four drilled shafts was conducted to determine the effect of high strength steel reinforcement bars on lateral resistance, steel casing on axial and lateral resistance, and steel casing without internal reinforcement on lateral resistance. Thermal Integrity Profiling (TIP) Thermal Wires and crosshole sonic logging (CSL) access tubes were installed in each shaft, and thereafter the corresponding non-destructive testing (NDT) was performed on each shaft to assess the integrity of the shafts and to compare the results from the different NDT methods. The results of the CSL tests using scored PVC tubes are compared against those conducted in 73/56 fully-threaded steel hollow bars, whereby the results indicated that the threaded bars served as a good host for performing the CSL tests. The data from the TIP Thermal Wires is compared against the results from the CSL tests for each of the four shafts, and the similarities and discrepancies between the two methods are discussed. This paper will serve as a reference to those interpreting the measurements and data obtained by performing nondestructive integrity tests on drilled foundations.INTRODUCTIONNon-destructive tests (NDTs) embody a set of critical tools for the evaluation of the integrity of constructed deep foundations, particularly for cast-in-place foundation elements. Construction defects may require the rejection of the foundation element by the owner’s representative, resulting in costly repairs or replacements and delays to the project schedule. The use and appropriate interpretation of the results from the NDTs provide the information required when evaluating the integrity of these constructed elements. A cooperative research program was conducted to assess the effects of various construction variables on the axial and lateral performance of drilled shaft foundations, which provided an opportunity to compare the established Crosshole Sonic Logging (CSL) test method to the newer Thermal Integrity Profiling (TIP) Thermal Wire method. This paper presents an overview of the experimental program performed at the geotechnical test site at Oregon State University (OSU), details of the CSL and TIP installation and testing methods, and the results of the NDTs on the constructed drilled shafts. Because one of the shafts was constructed with fully-threaded longitudinal steel hollow bars, this experimental program also allowed the assessment of the use of the hollow bars as access tubes for the CSL tests. Both the CSL and TIP test methods indicated that the shafts were of good quality and free from defects or anomalies; the data obtained using the TIP method also provided an estimate of the as-constructed shaft diameter and the reinforcement cage alignment, which will prove helpful when back-calculating axial and lateral load transfer during future loading tests."

Jan 1, 2016

By Kiyotaka Ohno, Nobushige Yasuoka, Yosuke Hioki

"The diameter of improved columns adopted by the original DJM Method had been 1000 mm, however, in order to comply with the social need for construction cost reduction, the Expanded Dry Jet Mixing (EX-DJM) Method with maximum column diameter expanded to 1300 mm was developed between 1998 and 2001 and has been widely applied since then. From the first application of EX-DJM in January 2002 for a first construction project, the total volume of improved soil has reached 325,000 m3 in 17 projects up to September 2014. Because of the advantages of the EX-DJM such as reduction of construction costs and periods leading to reduction in the number of improved columns, adoption of this method is expected to increase in the future. This paper describes the advantages of the EX-DJM, its construction results and case examples including those applied to restoration projects after the Great East Japan Earthquake, 2011.1. BACKGROUND OF DEVELOPMENTThe Dry Jet Mixing (DJM) Method is a soil stabilization method in which a powdery or granular binder is pneumatically fed into and mixed with soft soil to induce chemical reactions that stabilize and strengthen the soil. It was developed by government - private collaboration in Japan between 1977 and 1979. Up to March 2014, the total volume of soil improved by DJM method reached 33,500,000 m3. The initial diameter of improved columns of the original DJM Method was 1000 mm. In order to comply with the social need for construction cost reduction, the Expanded Dry Jet Mixing (EX-DJM) Method with maximum column diameter 1300 mm was developed between 1998 and 2001.2. ADVANTAGES OF EX-DJMThe construction equipment for the EX-DJM consists of two major parts, which are DJM machine and binder plant are shown in Fig. 1.The construction machine is of double mixing-shaft type with its column diameter expanded to 1200mm or 1300mm. In association with the increase in the column diameter, the binder feeder has also increased its discharge rate by approximately 1.69 times. Same as the increase rate of the area of original diameter 1000mm to diameter 1300mm are shown in Fig. 4."

Jan 1, 2015

By Kenneth R. Chadwick, Thomas J. Tuozzolo, Terence P. Holman

"Micropiles are often installed to retrofit existing foundations that experience distortion and to underpin structures prior to future construction. The Dublin Road Pump Station project is an example of retrofitting due to a basal failure during construction that compromised the bearing capacity of the soils. A completed pump station settled and had to be restored to its original position, and work could not proceed until a new support system for the partially completed wet well could be designed and installed. The project involved the construction of three below-grade structures for a new pump station in a growing area of Jackson Township, N.J. The general contractor constructed three pump station structures consisting of a pump chamber, wet well and an inlet chamber in early 2006.The geologic conditions beneath the project site (Figure 1) consisted of loose/soft to medium dense/stiff sand, silt and clay to a depth of 40 ft below ground surface, underlain by medium dense to dense glauconitic silty fi ne sand. When the general contractor was constructing the wet well, which involved an internally supported sheet pile excavation 32 ft below the ground surface and 28 ft below the static groundwater level, basal failure, boils and ground loss occurred. Driven piles were installed to support the wet well structure, but additional ground loss was observed within and outside the sheet pile excavation, followed by settlement of the adjacent pump chamber structure. Post-failure investigations were conducted by Mueser Rutledge Consulting Engineers, N.Y. (MRCE), a geotechnical and foundation engineering consultant. Their investigation concluded that the ground losses around the pump station structures had compromised the supportive capabilities of the natural subsoils.The owner engaged Moretrench, a geotechnical specialty contractor, to work with MRCE to develop a constructible solution to support the pump station structures in general and to restore the pump chamber to its original position. Knowing that ground loss had already occurred as a function of the initial basal heave and subsequent pile driving, the team selected micropiles as the preferred foundation element, primarily due to their flexibility in bypassing these disturbed zones and generating capacity as a function of grouting volume and pressure. Drilled piles were also recommended due to concerns about causing additional settlement of the pump chamber if driven piles were used."

Jan 1, 2008

By Mohamed Mekkawy, William W. Wheaton, Ira Brotman

"The Virginia Port Authority and the U.S. Army Corps of Engineers are partnering to construct the Craney Island Eastward Expansion (CIEE) to meet the dual purpose of extending the life of Craney Island as a dredged material management area and providing land for a state-of-the-art marine terminal. The over 500-acre (200-hectare) expansion provides additional upland dredged material capacity for the Hampton Roads Harbor by constructing perimeter dikes, that once filled, will provide land for the development of a container terminal. In the winter of 2010/2011 the first stage of sand fill was placed, followed by the installation of approximately 12 million linear feet (MLF) (3.6 million linear meters, MLM) of marine PVDs. With over 36 MLF (10.9 MLM) of PVD required to complete dike construction the project will be one of the largest PVD installation project in the U.S.This paper details the challenges associated with the construction of the cross dikes, in particular the design, testing, installation and monitoring of prefabricated vertical drains (PVDs) installed overwater to depths of over 130 feet (40 meters) for foundation improvement in the insitu very soft Norfolk Clay. With expected settlements of 20–30 ft (7-10 m) and 30 percent average strains, the discharge capacity of the PVDs was of particular concern. Laboratory data is presented showing the magnitudes and variability of discharge capacity under different confining pressures in both a straight and buckled condition.The method of installation and monitoring of the marine PVDs in open water included developing a specialized barge and sophisticated positioning and data collection system to verify installation location, depth of penetration and track quantities. An observational method, including material testing, detailed surveys, periodic in-situ testing, and instrumentation, was utilized by the project team to assess the project’s progress and allow for validation of consolidation and strength gain rates and magnitudes."

Jan 1, 2017

By Ira Brotman

The Virginia Port Authority and the U.S. Army Corps of Engineers are partnering to construct the Craney Island Eastward Expansion (CIEE) to meet the dual purpose of extending the life of Craney Island as a dredged material management area and providing land for a state-of-the-art marine terminal. The over 500-acre (200-hectare) expansion provides additional upland dredged material capacity for the Hampton Roads Harbor by constructing perimeter dikes, that once filled, will provide land for the development of a container terminal. In the winter of 2010/2011 the first stage of sand fill was placed, followed by the installation of approximately 12 million linear feet (MLF) (3.6 million linear meters, MLM) of marine PVDs. With over 36 MLF (10.9 MLM) of PVD required to complete dike construction the project will be one of the largest PVD installation project in the U.S. his paper details the challenges associated with the construction of the cross dikes, in particular the design, testing, installation and monitoring of prefabricated vertical drains (PVDs) installed overwater to depths of over 130 feet (40 meters) for foundation improvement in the insitu very soft Norfolk Clay. With expected settlements of 20?30 ft (7-10 m) and 30 percent average strains, the discharge capacity of the PVDs was of particular concern. Laboratory data is presented showing the magnitudes and variability of discharge capacity under different confining pressures in both a straight and buckled condition. The method of installation and monitoring of the marine PVDs in open water included developing a specialized barge and sophisticated positioning and data collection system to verify installation location, depth of penetration and track quantities. An observational method, including material testing, detailed surveys, periodic in-situ testing, and instrumentation, was utilized by the project team to assess the project?s progress and allow for validation of consolidation and strength gain rates and magnitudes.

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 David S. Graham, Benjamin Turner, Paul J. Axtell

Seismic challenges were at the forefront of design for two parallel replacement bridge structures over the Arkansas River as part of the I-30 Crossing Project in Little Rock, Arkansas. Although not an area of the country typically associated with high seismicity, proximity to the New Madrid Fault Zone resulted in design ground motions sufficient to trigger liquefaction in alluvial channel and point bar deposits. A detailed post-award subsurface investigation program utilized CPT with complimentary borings to obtain samples for laboratory testing to assess the continuity of potentially liquefiable layers, from which we concluded that continuous zones of liquefaction across the extent of the north approach could lead to lateral spreading towards the river. An overview of the foundation and superstructure design to resist lateral spreading forces in accordance with the latest published design guidelines and research is presented. Other seismic aspects of the design are covered including timber pile ground improvement to mitigate liquefaction at the north approach embankment and foundation input motions that differ from code-based ground surface motions due to foundation stiffness, strength, and geometry. The project showcases an example of successful collaboration between geotechnical and structural designers with contractor input to address seismic challenges in the South Central US. Furthermore, the importance of considering kinematic demands on columns and other superstructure components – not just foundations – is highlighted.

Sep 8, 2021

By Oladayo O. Komolafe and Majid Ghayoomi

p-y curves have been used over the years to determine the lateral resistance of piles. This method is popular among practicing engineers due to its simplicity and its ability to determine the slope, displacement, shear force, and bending moment for various depths along the pile. The ultimate lateral load resistance is a key component of p-y curve formulation. The p-y curve formulation by Reese et al. (1974) does not consider the effects of soil’s degree of saturation on theoretical ultimate lateral resistance of the failure wedge. This limits an accurate assessment of the lateral soil resistance near the ground surface and the consequent p-y curves. This paper extends the existing approach for determining the failure wedge in unsaturated cohesionless soils with suction dependency, especially for the depths that are above the water table within the wedge. The modification to the failure wedge analysis was made by considering the variation of the degree of saturation which affects effective stress and lateral earth pressure. Through a set of parametric analyses, the impact of incorporating principles of unsaturated soil mechanics in the estimation of theoretical ultimate lateral resistance is examined, and its implications on lateral pile response are discussed.

Sep 8, 2021

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 K. Rainer Massarsch

"Part 2 of 2 (Continued from Summer 2004 edition) By K. Rainer Massarsch, Geo Engineering AB, Stockholm, SwedenVibrations, which are caused by the installation of piles in dry or permeable soils, can cause settlements. The magnitude of settlements depends on several factors, such as soil type and stratification, ground water conditions (degree of saturation), pile type and method of pile installation (driving energy). A method of settlement prediction due to construction-induced vibrations has been presented by Massarsch (2000). However, in many cases, an engineering assessment must be made at an early stage of a project. The following simplified procedure can be used to estimate settlements in a homogeneous sand deposit adjacent to a single pile, Fig. 5. This approach is based on extensive experience from soil compaction projects. It is assumed that intense densification due to pile penetration occurs within a zone corresponding to three pile diameters. The volume reduction resulting from the propagating vibrations will cause settlements in a cone with an inclination 2V:1H, with the tip at a depth of 6 pile diameters. Thus the settlement trough will extend a distance of 3D+L/2 from the centre of the pile, with maximum settlements at the centre of the pile. Maximum settlements, Smaxand average settlements, Smax can be estimated using the following relationship, choosing an appropriate a value of the soil compression factor, from Table 2.The driving energy depends on the method of pile installation, soil stratification and the pile type. The displacement volume of the installed pile has been neglected. The simplified method is applicable for estimating settlements at the perimeter of a pile group. It should be noted that settlements also occur outside the assumed cone, but these are often negligible. The effect of incompressible layers should be taken into account by adjusting the effective pile length."

Jan 1, 2004

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Sep 8, 2021