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By John E. Lens

Driving bridge foundation piles into glacio-fluvial sands and gravels and glacial tills brought surprisingly longer than predicted driving lengths on several recent projects in Vermont. In some instances, piles drove more than 40 feet past refusal depths predicted from Standard Penetration Resistances from borings terminating in glacial till. Overall, piles developed substantially less skin friction than predicted using common capacity formulas and drove as much as 80 feet longer than predicted in the moderate to dense gravelly and cobbly soils. These piles were driven for one to five span highway bridges within narrow valleys with bedrock ranging from 80 to over 200 feet deep. Piles were for both conventional and integral abutment bridges. H-piles were used for a variety of reasons including lower unit cost, better availability, and better ability to drive through cobbly soils in upper strata. Dynamic testing was used to evaluate capacity, including skin friction and end bearing capacity. In order to develop better pile length and capacity predictions for future projects, VTrans and one of their geotechnical consultants are collaborating to develop criteria for improved pile capacity predictions in these river valleys. We are doing this by evaluating driving and dynamic testing data from four projects in comparison with the Federal Highway Administration (FHWA) DRIVEN pile design software, and methods from Myerhof (1976) and Tomlinson (1981). Our overall objective is to provide a basis for choosing appropriate pile types and reliably estimating pile lengths for projects in this terrain. Bridge foundation design projects in other mountainous terrain share similar design and construction challenges to those encountered in these Vermont projects. These include: difficult exploration drill rig access requiring smaller rigs with limited capability to drill through cobbles and boulders deep enough to reach bedrock; limited experience with displacement piles as alternatives to H-piles in this geology; and relatively greater variability in soil stratigraphy between foundations at these sites as a consequence of the relatively high energy depositional environment in mountainous terrain. This paper presents the case history summaries of the pile driving, results of the ?back analysis? capacity evaluations, examples of solutions employed on these projects to address the lower capacities achieved, and resulting pile capacity design guidelines and prediction criteria for these geologic conditions based on data from these projects.

Jan 1, 2007

By Gordon Chen

As part of a value engineering envisioned by East Coast Slurry, Weidlinger Associates, Inc. designed a unique elliptical slurry wall cofferdam for construction of the 65 ft. deep MWRA North Dorchester Pump Station. A conventional rectangle cofferdam with multiple levels of bracing would have been time consuming and costly and imposed a significant obstruction to the pump station construction. A circular slurry wall, while eliminating the bracings, conflicted with adjacent structures and required excessive backfilling around the final pump station structure. The ellipse shaped cofferdam fit the needs of the project well; however, it created a significant design challenge without the use of bracings. Unlike a circular cofferdam which primarily only has hoop stresses, the ellipse still has to be designed for horizontal bending moments in each panel because of the non-axial symmetric conditions. The more eccentric the cofferdam shape; the higher the horizontal bending. The challenge was to develop a three dimensional finite element model that could analyze both the hoop stresses and horizontal bending stresses above and below the bottom of excavation induced by soil and water pressure and unbalanced construction surcharge loads. This paper discusses the techniques used to model the soils and structure interactions and results of stresses on this challenging unbraced configuration.

Jan 1, 2010

By Walter G. Brusey

This paper describes a comprehensive pile test program conducted at John F. Kennedy International Airport (JFKIA) to evaluate pile types and design capacities ranging from 890 to 4450 KN (100 to 500 tons). Driven cased piles and drilled shafts, both standard construction and post-grouted after installation, were tested with platform loads extending to 8900 KN (1,000 tons). Alternate load test procedures were developed, extensive structural integrity testing and dynamic load tests were performed on selected shafts. A brief update is provided covering the application of results of the test program to pile selection for support of major structures incorporated in the on going redevelopment of JFKIA.

Jan 1, 2000

By Paul Summers, Kevin Richardson, Willem (Billy) Villet, Paul J. Sabatini, Attasit Korchaiyapruk, Edward C. Clukey

"A deep mixing method (DMM) foundation was selected by the Project Team for a very large LNG facility in West Africa. As described in a companion paper, this foundation consists of a large number of columns installed by mixing cement with in-situ soils. The foundations are arrayed as a variety of honeycombed type configurations which, if installed to desired specifications, can provide a robust foundation alternative. The foundation is capable of distributing loads and limiting settlements even if some of the soil in the columns is not fully mixed during installation. An important part of the overall quality assessment program, therefore, involved developing a testing program to verify the methodology. In addition the impact of potential defects in columns on the overall foundation integrity had to be assessed. This paper describes some of the preliminary work done to establish the requirements for the quality assurance program. A key component of this program involved the sampling frequency used to assess potential defects in the columns. To verify the column integrity 104- mm samples were taken continuously at a selected frequency through the 23 m long columns. The preliminary work described in this paper demonstrated that the appropriate sampling frequency depends on both the desired reliability level as well as the number of defective columns encountered during testing.Initial finite element analyses were performed to assess the extent that defects could occur in columns within the honeycombed structure without adversely affecting the overall foundation integrity. The results from this work demonstrated that the spatial location of the defects was critical to properly assessing the foundation integrity.In addition to column sampling a load test was performed as part of the foundation verification process. The methods used to apply appropriate loads so that loads at the bottom of the columns approached design values are discussed in the paper.The results obtained from this preliminary study were then used to help develop a more comprehensive assessment program, described in a companion paper, to determine the robustness of the DMM foundations for both the LNG processing facilities and a condensate tank.IntroductionFoundations constructed with the Deep Mixing Method (DMM) can be an attractive and cost efficient alternate to other deep foundation options. This foundation is constructed by mixing soil and cement with an auger type drill. The foundation is usually constructed with a dual auger system that simultaneously creates two contiguous columns called foundation elements. Many elements are then arranged in a honeycombed configuration to create the overall foundation (Figure 1). A desired column strength can be obtained by varying the volume of cement added to the columns, the mixing rate of the soil and stroking sequence."

Jan 1, 2017

By Edward C. Clukey

A deep mixing method (DMM) foundation was selected by the Project Team for a very largeLNG facility in West Africa. As described in a companion paper, this foundation consists of alarge number of columns installed by mixing cement with in-situ soils. The foundations arearrayed as a variety of honeycombed type configurations which, if installed to desiredspecifications, can provide a robust foundation alternative. The foundation is capable ofdistributing loads and limiting settlements even if some of the soil in the columns is not fullymixed during installation. An important part of the overall quality assessment program,therefore, involved developing a testing program to verify the methodology. In addition theimpact of potential defects in columns on the overall foundation integrity had to be assessed.This paper describes some of the preliminary work done to establish the requirements for thequality assurance program. A key component of this program involved the samplingfrequency used to assess potential defects in the columns. To verify the column integrity 104-mm samples were taken continuously at a selected frequency through the 23 m longcolumns. The preliminary work described in this paper demonstrated that the appropriatesampling frequency depends on both the desired reliability level as well as the number ofdefective columns encountered during testing. Initial finite element analyses were performed to assess the extent that defects could occur incolumns within the honeycombed structure without adversely affecting the overall foundationintegrity. The results from this work demonstrated that the spatial location of the defects wascritical to properly assessing the foundation integrity. In addition to column sampling a load test was performed as part of the foundationverification process. The methods used to apply appropriate loads so that loads at thebottom of the columns approached design values are discussed in the paper. The results obtained from this preliminary study were then used to help develop a morecomprehensive assessment program, described in a companion paper, to determine therobustness of the DMM foundations for both the LNG processing facilities and a condensatetank.

By Carl-Oscar Nilsson, Åke B. Nilsson

"The embankment dam at Storfinnforsen is 23 m high and was completed in 1954. The dam has an impervious zone with timber sheet piles and a support fill of glacial till. The pore water pressure in the downstream shoulder has during recent years increased due to deterioration in the sealing function of the timber sheet piling. There is a concern that the high pore water pressure in the glacial till will cause internal erosion initiating at a thin coarse transition layer between the glacial till and the rock fill along the downstream toe. As a remedial action in order to improvement of the leakage resistance a supporting berm of coarse rockfill against the downstream slope of the dam was constructed in year 2013. In addition a new impervious seal in the centre of the dam e.g. a diaphragm wall was considered. However, after further studies and a trial stretch of 40 drains each 20 m long and diameter 0.3 m an alternative with vertical drilled drains in the downstream support was selected. A contract has now started up to drill in a similar way to treat the full length of the dam with drains. The work is in the planning to be completed in 2016.Dam ConstructionStorfinnforsen Embankment Dam was put into operation in 1954. The dam is 330 m long and maximum height is approximately 23 m. The dam is constructed with a central core zone and supporting zones of earth and rockfill on the upstream and downstream sides giving an almost symmetrical cross-section about the dam axis, see Fig. 1. The upstream slope is 2H:1V down to el. 270 and 2.5H:1V below. On the downstream side the slope is 1.75H:1V down to +269 and 2H:1V below. The core zone consists of a timber sheet pile wall with a Zone 5 of glacial till, approximately 2 m wide, adjacent to the wall on the upstream side."

Jan 1, 2016

By Goudschaal Mark R.

"The Museum of Science and Industry U-505 Submarine Relocation project in Chicago, IL consisted of building an underground reinforced concrete vault (37' deep) for the Museum's new U-505 exhibit. This WWII submarine was captured in 1944, had been located outdoors at the Museum since 1954 and was lowered into its new exhibit area in 2004. A unique combination of earth retention, water cut-off and underpinning systems allowed a forty-two foot (42') deep excavation underneath th is historic museum. The museum - originally built in 1893 for the Chicago World's Fair - was closely monitored for building movements throughout construction. The underpinning systems, construction activities and monitoring results are presented herein. IntroductionThe historic U-505 German submarine at the Museum of Science & Industry was restored, moved approximately 1,000' and then lowered into its new indoor home (Figures 1, 2 and 3). The new underground exhibit opened this year celebrating the 61st anniversary of the German submarine's capture on June 4, 1944. On this historic day, Captain Daniel V. Gallery, a Chicago native, led the Navy in the siege of this submarine near the coast of Africa. This U-boat was the only German sub captured by the United States Navy in WWII and the Enigma machines, codebooks and publications recovered from the sub helped the war effort."

Jan 1, 2005

By K. S. Ho

With the aid of the advanced electronic devices and micro-processors, the quality control of deep foundations can be carried out by Non-Destructive Tests (NDT). Three methods are presented here: the Sonic Logging, Vibration and Stress Wave Analysis Methods. The principles, equipments used, testing procedures and applications are fully described. The correlation of these methods with the conventional tests (mechanical coring and loading test) are studied to give a better understanding of the methods. Several case histories with the test results obtained from a number of sites in Hong Kong and overseas are discussed to show how the pile quality can be examined and especially, how to confirm the effectiveness of remedial works on a defective pile. Recommendation on the percentage of piles to be tested are given at the end of the paper by using statistical method.

Jan 1, 2010

By John C. Ryan

The Emeca Pile Splice, an innovative mechanical prestressed concrete pile splice, is the first robotically welded splice to be fabricated in the United States. An analytical and experimental study was conducted to establish the capacity of the standard splice for 12-in. and 14-in. square piles. The study illustrates compliance of the splice with International Building Code (2006) requirements. A case study for a large petroleum tank foundation project in Port Canaveral, FL is presented, demonstrating the efficiency achieved through use of spliced-piles. For the case-study project, single-piece 18-in.-square, 100-ft-long piles were replaced with 12-in.-square, two-piece, spliced piles. As a result, a significant reduction of material, labor, handling, and equipment was documented for the project. Savings realized on the installed pile cost was estimated to be in excess of 30% by the owner.

Jan 1, 2010

By Donald Deardorff

"Helical piles often rely on the final installation torque for ultimate capacity verification. When helical piles are designed using traditional bearing capacity equations for deep foundations and field monitored for a specified final installation torque, a factor of safety equal to 2 is often allowed for the design. One of the more common methods of determining torque during helical pile installation is by correlating the differential pressure across a hydraulic gear motor to a torque. Most drive head manufacturers provide multipliers to convert differential pressure to torque for different drive head models. These multipliers are based on theoretical torque equations and vary with the planetary gear ratio, hydraulic gear motor displacement and drive head efficiency. Drive head manufacturers show a linear fit between the differential pressure and output torque with no scaling effect. Previous drive head testing performed by the author has confirmed that the drive head differential pressure to torque relationship is generally linear however there is a scaling adjustment needed. This results in a variation of multipliers across the differential pressure range for a given drive head.Eight hydraulic drive heads from three manufacturers were field tested by Foundation Supportworks, Inc. to compare the torque versus differential pressure curves with varying installation equipment, hydraulic line sizes and hydraulic flow rates. Differential pressure was monitored using three methods including pressure gages, PT-Tracker and an Ashcroft AT-100. Flow and temperature was measured using a Webtech system analyzer. Torque was measured using a Pro-Dig in-line torque transducer, a TruTorque indicator and a Chance Mechanical Dial in-line torque indicator. The current testing indicates that a change in installation equipment and/or a change in hydraulic flow rate may affect the torque versus differential pressure curve of a given drive head. The results of this testing also show that some of the methods for determining torque during helical pile installations may be unconservative, thereby resulting in safety factors less than required."

Jan 1, 2017

By Donald Deardorff

Helical piles often rely on the final installation torque for ultimate capacity verification. When helical piles are designed using traditional bearing capacity equations for deep foundations and field monitored for a specified final installation torque, a factor of safety equal to 2 is often allowed for the design. One of the more common methods of determining torque during helical pile installation is by correlating the differential pressure across a hydraulic gear motor to a torque. Most drive head manufacturers provide multipliers to convert differential pressure to torque for different drive head models. These multipliers are based on theoretical torque equations and vary with the planetary gear ratio, hydraulic gear motor displacement and drive head efficiency. Drive head manufacturers show a linear fit between the differential pressure and output torque with no scaling effect. Previous drive head testing performed by the author has confirmed that the drive head differential pressure to torque relationship is generally linear however there is a scaling adjustment needed. This results in a variation of multipliers across the differential pressure range for a given drive head. Eight hydraulic drive heads from three manufacturers were field tested by Foundation Supportworks, Inc. to compare the torque versus differential pressure curves with varying installation equipment, hydraulic line sizes and hydraulic flow rates. Differential pressure was monitored using three methods including pressure gages, PT-Tracker and an Ashcroft AT-100. Flow and temperature was measured using a Webtech system analyzer. Torque was measured using a Pro-Dig in-line torque transducer, a TruTorque indicator and a Chance Mechanical Dial in-line torque indicator. The current testing indicates that a change in installation equipment and/or a change in hydraulic flow rate may affect the torque versus differential pressure curve of a given drive head. The results of this testing also show that some of the methods for determining torque during helical pile installations may be unconservative, thereby resulting in safety factors less than required.

By Kamil Nuzha, Jianchao Li, Bashar S. Qubain

"The Philadelphia Water Department is rehabilitating Belmont Raw Water Basin. As part of this work, a 500-ft long, temporary cofferdam was designed to retain 35 ft of combined water and soil at the western half during the reconstruction of the eastern half. A cofferdam that comprises two integral rows of sheet piles was selected to take advantage of the soil’s weight between the sheet piles for increased stability. To fine tune the design, a geotechnical investigation was carried out to verify the subsurface conditions and, in particular, the top of rock variations along the centerline of the cofferdam. A detailed finite element analysis was performed based on the subsurface findings and incorporating the construction sequence to evaluate the behavior of the cofferdam at the following stages: installation of tie rods to connect to the two rows of sheet piles; partial excavation and installation of tiebacks; complete excavation of the east basin, and demolition of the cofferdam. Inclinometers and survey markers were installed every 100 ft along the cofferdam and were monitored throughout construction. The deformation measurements were in good agreement with the finite element results.INTRODUCTIONThe Philadelphia Water Department (PWD) Belmont Raw Water Basin is located at the intersection of City Line and Belmont Avenues in Philadelphia, PA. The facility actually contains two raw water basins, east and west, separated by an earthen dividing dike. Water leakage at the bottom of the basins and through the dividing dike together with increasing demand for a larger storage capacity dictated the replacement of the wide earthen dike with new narrower concrete structure. The temporary cofferdam was designed for a two-year period to facilitate excavation support, water cutoff, removal of the existing earthen dike and replacing it with a new concrete dike. During this construction sequence, the water level in the west basin had to be maintained at or near its full capacity.Various excavation support systems were considered for this project prior to the selection of a double wall sheet pile cofferdam. Fig. 1 shows a plan view of the cofferdam and the new dividing dike. A typical cross section of the two structures is shown in Fig. 2. Double row sheet pile walls are commonly used as both temporary and permanent retaining systems in open water applications such as construction works, quaywalls, breakwaters and revetments for storing industrial waste as indicated by Ohori, et al. (1984), Ohori et al. (1988), and Khan, et al. (2001). There are many advantages to double row sheet pile systems as recognized by Ohori, et al. (1984; 1988): (1) It can be installed and removed in the presence of water easily and quickly; (2) it provides stability with small width to height ratio, utilizing the existing soils between the installed sheet pile rows; and (3) it serves well as a means for water cutoff. These advantages meet the specific project requirements."

Jan 1, 2016

By Charles M. Wilk

"Mass stabilization involves mixing binding agents into marginal or contaminated soil to improve the subject material’s physical and/or chemical properties. This paper concentrates on the principles of soil mixing and benefits and application to new and existing rail right-of-way. Successfully applied in Scandinavia and other European countries, the soil mixing is now being applied in right of way in the northern latitudes of the U.S. and Canada. These regions have significant areas of “peaty” soils that can complicate construction and maintenance of rail and structure foundations. Mass stabilization can be used to improve the bearing strength of these soft soils for subsequent construction of railroads, pipelines, roads, and buildings. In civil engineering, the technology is often used to improve the construction properties such as bearing strength, of a marginal soil. In environmental engineering, stabilization is remediation treatment technology that protects human health and the environment by immobilizing hazardous constituents within the treated material. . The treatment is conducted while the subject material remains in-place (insitu). Mass Stabilization is often used to accomplish both civil and environmental purposes on the same project effectively addressing marginal soil while eliminating the expense of soil removal and replacement.This paper presents the principles of mass stabilization technology, implementation in the field and recent completed railway projects.The example rail projects will present the various benefits that soil mixing provides to railway construction and maintenance. Bench-scale studies and full scale implementation as well as soil construction properties before and after mass stabilization will be discussed. The paper and presentation will include information on the advantages of mixing methods and binding agent delivery systems.INTRODUCTIONNew or existing railroad right-of-ways may cross ground with low bearing capacity. Right of way subgrade undergo deflection (strain) as loads (stress) are applied (1). The amount of strain or deflection of the subgrade caused by loading of a train is proportional to the stiffness of the subgrade materials. Some soils, such as tamped ballast, are very stiff and resist loads well. Other soils such as soft clay, peat, or loose sand have low stiffness and undergo substantial movement under loads. It is very desirable to have the stiffest possible material in a track subgrade. Stiff subgrade material limits deflection under load, reducing track roughness and occurrence of track defects. Mass stabilization is a geotechnical method that can be used to improve the bearing capacity or stiffness of soil in these right-of-way. Mass stabilization involves mixing binding agents into soil subject to treatment while the soil remains in-place or insitu. Variations in the design or areas subject to treatment can be used to address transmission of vibration to adjacent structures."

Jan 1, 2017

By Xuhui

Pile foundations are underground projects which are carried out under complicated site conditions, so it is difficult to summarize their characteristic patterns from the everchanging practical pile foundations. In combination with theories, the paper analyses the effects of sound reinforced concrete piles and various types of defective piles on the propagations of stress waves. Through testing on prototype pile models, by use of the transient dynamic method and comprehensive analysis in both time domain and frequency domain, their reflection characteristics and patterns are acquired. In addition, discussions are carried out in combination with some real projects. Our model tests include comparison of large scale pile models of 20X20cm in cross section, 5. 0m in length respectively in air, standard sand, and natural stratum; prototype model tests of digged piles of 0. 7-1. 2m in diameter, and 18m, 30m in length; prototype model tests of bored piles of 0. 6m, 0. 8m in diameter, 12-20m in length. Test results show that no matter in air or buried in medium, the intrinsic characteristics of sound piles and various types of defective piles are fixed. In their time domain waveforms and spectral diagrams, obvious regularity are shown, which proves that the relations between the pile natures and their dynamic responses are fixed, which provide basis for correct judgement of pile soundness and natures of defective piles.

Jan 1, 1991

By Peter Iovino

Unfortunately, I don't know the unit cost per cubic yard of treatment. I reflected on that yesterday and I don't think that we considered the use of micropiles. They could have been an option. The challenge may have been picking up some of the lateral load but I think the micropiles could have been installed on a batter and perhaps extended to rock. We could have considered them, but I do not believe we explored micropiles as an option for this project.

Feb 10, 2003

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 Charles M. Wilk

"Mass stabilization involves mixing binding agents into marginal or contaminated soil to improve the subject material’s physical and/or chemical properties. This paper concentrates on the principles of soil mixing and benefits and application to new and existing rail right-of-way. Successfully applied in Scandinavia and other European countries, the soil mixing is now being applied in right of way in the northern latitudes of the U.S. and Canada. These regions have significant areas of “peaty” soils that can complicate construction and maintenance of rail and structure foundations. Mass stabilization can be used to improve the bearing strength of these soft soils for subsequent construction of railroads, pipelines, roads, and buildings. In civil engineering, the technology is often used to improve the construction properties such as bearing strength, of a marginal soil. In environmental engineering, stabilization is remediation treatment technology that protects human health and the environment by immobilizing hazardous constituents within the treated material. . The treatment is conducted while the subject material remains in-place (insitu). Mass Stabilization is often used to accomplish both civil and environmental purposes on the same project effectively addressing marginal soil while eliminating the expense of soil removal and replacement. This paper presents the principles of mass stabilization technology, implementation in the field and recent completed railway projects. The example rail projects will present the various benefits that soil mixing provides to railway construction and maintenance. Bench-scale studies and full scale implementation as well as soil construction properties before and after mass stabilization will be discussed. The paper and presentation will include information on the advantages of mixing methods and binding agent delivery systems.INTRODUCTIONNew or existing railroad right-of-ways may cross ground with low bearing capacity. Right of way subgrade undergo deflection (strain) as loads (stress) are applied. The amount of strain or deflection of the subgrade caused by loading of a train is proportional to the stiffness of the subgrade materials. Some soils, such as tamped ballast, are very stiff and resist loads well. Other soils such as soft clay, peat, or loose sand have low stiffness and undergo substantial movement under loads. It is very desirable to have the stiffest possible material in a track subgrade. Stiff subgrade material limits deflection under load, reducing track roughness and occurrence of track defects. Mass stabilization is a geotechnical method that can be used to improve the bearing capacity or stiffness of soil in these right-of-way. Mass stabilization involves mixing binding agents into soil subject to treatment while the soil remains in-place or insitu. Variations in the design or areas subject to treatment can be used to address transmission of vibration to adjacent structures."

Jan 1, 2015

By Dinesh R. Katti

Caissons which are locally known as well foundations, which may very in diameter from 30 m to more than 30 m and in majority of the cases having depth to diameter ratio between 1 to 1.5, are normally used to support piers of long span bridges or tall structures, which transmit high magnitude of axial load, horizontal thrust and moment. On the basis of depth to diameter ratio the foundation system appears to fall in the category of shallow foundations but due to deep excavation, it is observed that part of the moment acting on the caisson is shared by due the sides due to development of passive resistance. The problem is statically indeterminate and three dimensional in nature. To ascertain the various parameters needed for design, such as moment shared by base and sides, horizontal and vertical displacement and tilt, and base and side contact pressure diagrams need to be obtained from nondimensional relations of parameters with respect to D/B ratio derived from large scale model studies conducted by Katti etal at IIT, Bombay under MOT Project between 1976 and 1988 and later on at UNEECS. On the basis of above data on attempt is made to put forward guide lines for selection of parameters for design of caisson foundations / well for following cases for opening us some discussion. The cases are cohesive soil at the side and cohesive soil, or sand or soft rock or hard rock at the base.

Jan 1, 1996

By Athul Prabhakaran, Ramin Motamed, Ahmed Elgamal, Milad Jahed Orang, Reza Boushehri

Documented case histories from past earthquakes have exhibited the devastating effects of the liquefaction phenomenon on the performance of buildings that are often presented in the form of excessive settlement of shallow foundations. Example earthquakes include the 1964 Niigata earthquake in Japan, and more recently the 2010-2011 Canterbury Earthquake Sequence in New Zealand, and the 2011 Tohoku earthquake in Japan. All of the listed events comprised several examples of severe liquefaction-related damage to the buildings founded on shallow foundations. Although the liquefaction-induced building settlements have been experimentally studied extensively since 1964 using shake table tests and dynamic centrifuge experiments, studies focusing on cost-effective mitigation strategies are still limited. In this study, the performance of helical piles as a cost-effective countermeasure to minimize the damaging effects of liquefaction-induced ground settlements on buildings founded on shallow foundations is studied. Two large-scale shake table experiments were conducted at the University of California, San Diego (UCSD) to investigate the effectiveness of helical piles in liquefiable grounds. Results from these two experiments highlight a highly improved performance of a shallow foundation supported on helical piles. These largescale shaking table experiments demonstrate the efficiency of using helical piles as a cost-effective countermeasure to reduce the liquefaction-induced building settlement.

By Adrian M. Keller

Borehole televiewers are downhole inspection devices available for high-resolution imaging of a borehole wall following rock coring. Borehole televiewers should be considered by geotechnical engineers and geologists as a supplemental way of investigating rock for deep foundations. The optical televiewer (OTV) produces a digital optical image and the acoustic televiewer (ATV) utilizes reflected acoustic waves to produce images of the borehole walls. These devices can be utilized to examine soft or fractured zones in the rock mass, solution features, open joints or other voids not observable from traditional rock coring techniques. These devices along with computer post-processing can determine the strike and dip of joints, bedding planes, shear surfaces, or other structural features, eliminating the need for expensive oriented cores or manned downhole logging. An acoustic televiewer was utilized in the Fall of 2008 during the investigation phase for the I-70 New Mississippi River Bridge (I-70 MRB) in St. Louis, Missouri. Voids and fractures in the upper portion of the rock were described by prior consultants. Further investigation of these features was necessary to evaluate deep foundation options to support the main towers. Ten borings were drilled from a barge in the river at the two main tower pier locations. An ATV was utilized in each of the ten borings to produce images of the rock mass in the borehole and allow further investigation of the voids. Voids interpreted as solution features were readily identified in the ATV logs in multiple borings and at similar elevations, suggesting connectivity. Measurements of the voids? width, location in the borehole and orientation allowed a more thorough understanding of the potential impact the solution features may have on the planned deep foundations. An extensive grouting program was eliminated based on the ATV results.

Jan 1, 2010