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By Paul J. Sabatini

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

By Hyung-Min Kwon

There are a number of methods available that can be used to estimate the bearing capacity of piles that are subject to lateral load, such as the theory of subgrade reaction or the elastic continuum approach. The objective of these approaches is to determine the lateral load corresponding to the allowable lateral displacement of the pile. It is important to select the appropriate soil stiffness when analyzing soil behavior within the allowable displacement of piles because the stiffness of soil is dependent on the displacement of piles. Even though pressuremeter tests can measure the stress-strain behavior within a wide strain range, pressuremeter test results have been utilized to assess only the fragmentary soil modulus based on either semi-empirical correlations or analytical approaches. This study is concerned with a methodology that can estimate the horizontal deformational property, while taking into consideration the nonlinear deformational characteristics of sandy soils. Pressuremeter tests were conducted for 15 cases using a calibration chamber. Reloading curves were employed in the estimation of horizontal deformational property in order to minimize the effect of soil disturbance caused by the installation of the probe. The shear modulus degradation characteristics were estimated from the curve fitting for the reloading curve and from extrapolation using the exponential function. In addition, the difference was taken into account between the stress state around the probe in reloading and that of the in-situ state. A consistent relationship was observed between the maximum shear modulus taken from the suggested method and the bender element tests performed in the calibration chamber, simultaneously with the pressuremeter tests. In addition, the results showed significant concurrence with the well-known empirical correlation.

Jan 1, 2008

By Terence P. Holman

Micropiles are employed to retrofit existing foundations, including underpinning prior to future construction operations and resupport of existing structures that have experienced distortion and settlement. This paper presents analyses of the two case histories requiring the use of micropiles in these applications. The first case history involves micropiles used to resupport a settled pump station next to an excavation which had suffered basal failure and ground loss. A compression load test pile experienced plunging failure which, after analysis of the strain-gauge data acquired during the test, was attributable to a greater degree of disturbance to the subsoils beneath the site than anticipated. After construction of the micropiles around the pump chamber a synchronized jacking system was used to lift and right the 320 kip chamber structure, followed by resupporting it on the newly constructed piles. The second case history entails the use of micropiles for direct underpinning support of existing columns prior to a utility tunnel installation within an existing high-bay warehouse structure. The design constraint that most significantly affected the successful completion of this project was the desire to bond the new piles into the existing reinforced concrete foundations. As a result of the coring method through the footing, the ultimate bond stress measured during a pullout test was more than twice that assumed in the design. Monitoring of the underpinned columns during trench excavation indicated that the system performance was acceptable. These case histories reinforce the concept that lower capacity micropiles can provide a rapid means to underpin and retrofit existing structures.

Jan 1, 2007

By Michel Bustamante

The original Cistercian Lure abbey situated in eastern France and built in the second half of the 16th century, has become nowadays an administrative building. Because it has been founded on poor ground conditions and inadequate foundation scheme, the abbey has suffered severe structural distortion. In 1992 an inspection revealed new extensive damages which led to a general refection together with a foundation underpinning. Micropiling was the selected method. Movements recorded over a period of 6 years after underpinning completion are presented.

Jan 1, 2002

By Richard Stone, Rouzbeh Afsharhasani, Moses Karakouzian

"Caliche, a hardened sedimentary deposit of calcium carbonate that occurs worldwide, generally in arid or semiarid regions, is frequently encountered in Las Vegas, Nevada. The presence of a caliche layer in a soil profile affects the response of deep foundations to axial load. This paper studies the stiffening effect of caliche layers on the elastic settlement of a pile foundation. In order to evaluate the response in a layered soil-caliche profile, finite element analyses were performed on a typical-sized single pile and a pile group, both having constant diameter and length of the pile. The results indicate that the stiffening effect from the caliche is noteworthy, and a layer with a relative thickness of at least one pile width, regardless of its location, reduces the pile settlement for both single piles and group of piles systems by at least 50%.IntroductionThe presence of cemented materials in the soil profile influences the settlement response of foundations. One type of cemented material that can be found in arid places around the world is a sedimentary deposit of calcium carbonate called caliche. Caliche, a hardened sedimentary deposit of calcium carbonate, is common in arid and semi-arid urban areas, such as Las Vegas, Nevada (Wyman, et al. 1993).Caliche is mostly observed in lacustrine, river, and alluvial fan deposits (Jr.C.C 1970). It is also found in Central and Western Australia, the Kalahari Desert, the High Plains of the Western U.S., and the Sonoran Desert of the U.S. and Mexico.Some conditions required for the formation of caliche are that country or basement rocks must be a carbonate type, carbonate must be present in the soil zone of the area, climate regime is semi-arid to arid, there exists widespread capillary activity, and carbon dioxide (CO2) is present in the environment. As a result, caliche occurs as a product of the carbonization process (Atabey, Atabey and Kara 1998). In such areas where foundations are constructed on thin rock layers (caliche), special geotechnical design conditions should be considered, particularly if the supporting rock layer is underlain by a weaker material."

Jan 1, 2015

By Lawrence F. Johnsen

Six case histories are presented in which tall, slender high rises are supported on high capacity minicaissons. The recent development of a high strength rebar cage has resulted in compressive loads of up to 3400 kips on 24 inch diameter minicaissons. Provisions in the pending NYC building code will allow borehole video inspection in lieu of load testing. The ?new? technology results from the marriage of several well established methods: rotary duplex well drilling, high capacity micropiles and high capacity reinforced concrete building columns.

Jan 1, 2007

By Z. Q. Bian

The wireline sampling originates from core drilling in rocks. The authors combined the wireline sampling technique with conventional undisturbed soil samplers, including Osterberg sampler, Denison sampler and double tube barrel, and then developed the wireline samplers of WPS, WSS and WSR models. These samplers are able to sample various soils. They reserve all the advantages of the original samplers, and moreover, they are noted with quick hoisting and lowering by wire rope. Therefore, it becomes an efficient new technique of sampling undisturbed soil from deep foundation.

Jan 1, 2010

By Adel M. Hanna, Ibrahim M. Mashhour

"Collapsible soil is known as one of the difficult soils, which possesses considerable strength when it is dry and significantly reduced when inundated. In practice, in case of a thick layer, pile foundations are often used to penetrate the collapsible soil to firm soil/rock strata. Inundation of collapsible soil is accompanied by a large and sudden settlement, which may significantly increase the negative skin friction and accordingly the drag loads on the pile’s shaft. Inundation may take place from the running surface-water or raising the groundwater. In case of surface water, the amount of settlement varies, depending on the extent of the wetted zone and the degree of saturation in the soil, while rising groundwater will produce full saturation in the ground and accordingly larger settlement.In the literature, there is lack of reports dealing with the prediction of the drag load on piles in collapsible soils subjected to inundation. This is due to the complexity of modeling collapsible soil analytically. Alternatively; the results of a sophisticated experimental investigation may guide the researcher to develop a model to predict the drag load on these piles.This paper presents the results of a small-scale experimental investigation tailored to measure the soil collapse during inundation and the associated drag load on an endbearing pile’s shaft. Based on the results of the present investigation, the effect of the soil collapse potential and the pressure acting on the soil during inundation on negative skin friction is presented.INTRODUCTIONCollapsible soil is a metastable material, traditionally defined as unsaturated soils that experiences a radical rearrangement of particles and significant reduction of volume upon wetting with or without loading (Bara 1976; Houston et al., 1988). A wide range of soils fall into the category of collapsible soil, including naturally existing types of soils such as: Alluvial flood plains, mud flows, residual soils, colluvial deposits, fans, aeolian or wind-blow deposits sands and silts (loess), volcanic tuffs, gypsum, dispersive clays, loose cemented sands , sodium rich montmorillonite clays (Clemence and Finbarr 1981).Soil wetting and soil saturation may take place as a result of urbanization or natural causes, such as: groundwater level rise, landscape irrigation, broken water pipelines or sewer lines, poor surface drainage, groundwater recharge, cut/fill construction, and moisture increase due to capillary rise. The severity of the outcome depends heavily on the so called collapse potential of the soil, which depends mainly on; soil type, compaction effort, initial water content and stress level at soaking (Houston and Houston, 1997; Ayadat and Hanna, 2007)."

Jan 1, 2015

By Joseph T. Coe, Siavash Mahvelati, Philip Asabere

Characterization of existing foundations remains an important issue as foundation reuse and rehabilitation continue to garner increased attention. In the case of unknown foundations, geophysical and nondestructive testing (NDT) methods have been utilized in the past to evaluate foundation geometry and could serve as useful tools in the case of foundation reuse. A comprehensive study was initiated in the late 1990’s and early 2000’s that evaluated the effectiveness of the available geophysical and NDT technologies to characterize unknown foundations for scour evaluation purposes. At the time of that study, the Multichannel Analysis of Surface Waves (MASW) geophysical method was in its infancy and not widely used. Since then, MASW has become increasingly prevalent in geotechnical applications as the method presents a number of potential advantages when characterizing the subsurface, including rapid testing, increased signal to noise ratio, and ability to resolve velocity inversions. This paper presents a case study that explores the abilities of MASW as an unknown foundation characterization tool. MASW was applied to determine subsurface stiffness at a bridge foundation site in the Philadelphia metropolitan area. One MASW survey line was performed immediately over the foundation of interest and another was performed over a control zone adjacent to the foundation to establish a baseline site profile. The purpose of this testing was to examine whether MASW could establish the geometry of the foundation at this site. This paper presents the site conditions and MASW testing procedures, followed by a discussion of data analysis and interpretation.

Jan 1, 2016

By Barry C. Roth

Driving of large piles in water can impact marine wildlife. Bubble curtains can mitigate these adverse effects. The procedures for and preliminary results of monitoring airborne, waterborne and groundborne vibrations with and without bubble curtains on a test project involving 2.438 m piles to 110 m is reported here. We observed fish kills and sea lions apparently fleeing the area. These phenomena were presumably due to the extreme acoustic effects of the powerful hammers which generated waterborne sound intensities locally in excess of 240 dB. This waterborne pile driving noise data collection undertaking is believed to be the most extensive ever attempted.

Jan 1, 2001

By E. Ulrich Klotz

It is difficult to predict accurately the capacity of driven piles in sand. In practice, this uncer­tainty either leads to conservative designs if the capacity is under-predicted, or worse, if the capacity is over-predicted, it can lead to severe foundation problems. One significant possible cause of the problem is that currently available semi-empirical design methods do not capture the fundamental mechanisms that govern the load capacity of driven piles in sands. As part of a recent research project at City University centrifuge tests on a driven model pile in sands have been undertaken. A fully instrumented model pile was constructed and pushed into samples of quartz and carbonate sand thus covering a wide range of mineralogies. Tri-axial tests were used to determine the fundamental patterns of behavior of the sands. This allowed a general framework to be established, in which the in situ stress:volume relationship is shown to govern the capacity of the pile. The paper sets out with a brief introduction of the experimental techniques used in the study. The results of the pile tests are discussed in detail with particular attention given to distribution of the radial stresses along the pile shaft. Existing design methods for piles in sand are then discussed in the light of the new understanding gained from the research, highlighting their deficiencies and suggesting an improved approach.

Jan 1, 2002

By William M. Camp

Construction-induced earthborn vibrations have long been recognized as a potential problem with respect to the constructed environment and various vibration criteria are in use to prevent damage. A special case of construction vibration control is the protection of early-age or ?green? concrete. Unlike limits for damage prevention to building stock, there is no rational, widely accepted limit for protection of early-age concrete. Numerous criteria have been proposed or reported in the literature and the most relevant and rational proposals are summarized herein. These findings are applied to a case history involving both bored and driven piles. Vibration measurements were made during pile driving activities and the vibration magnitude was evaluated with respect to the exposure of freshly-placed and curing concrete to the earthborn vibrations. The maximum vibration magnitude at the applicable distances from pile driving was on the order of 0.3 inches per second. Based on the most persuasive literature, threshold values of 0.8 inches per second or even 1 to 2 inches per second for the protection of green concrete appear to be well-supported. Consequently, it was concluded that the pile driving activities and bored pile construction could proceed simultaneously.

Jan 1, 2010

By A. Ghorbani

The analysis of Combined Pile Raft Foundation (CPRF) is very complex due to involved interactions among components of CPRF system. Many researchers made efforts to develop sufficient methods including three dimensional finite element methods to compute these interactions. Since there are some restrictions and complexity in previous methods, in present study a new approach based on three dimensional finite difference methods is implemented to overcome some of these restrictions. The total and differential settlements of a centrifuge case study are computed using different numerical methods to show the performance of present numerical approach.

Jan 1, 2007

By Frank Rausche

The more widespread use of Augered Cast-in-Place (ACIP) Piles has generated increased demand for improved quality control measures. These deep foundation elements are often relatively long and slender and their structural quality depends on the experience of the installers, the adequacy of their drilling and pumping equipment, and of course, the properties of the soil. Since the concrete of ACIP piles is pumped under pressure into the borehole, the piles may achieve a very high unit shaft resistance if conditions are favorable and the piles are well constructed. Three types of methods can help assure that the piles are properly executed. During construction, monitoring the volume of concrete pumped and the pressure applied helps avoid structural defects. After installation, and once the concrete has hardened, the Pulse Echo Method allows for a check of the structural integrity of the shaft. Finally, a load test, performed some time after installation, yields a check of both bearing capacity and structural integrity of an individual pile. Because of their expense and associated construction delays, static load tests are normally done for only a few piles. However, at large construction sites, it may be necessary to perform many load tests either as a planned construction control activity or as a means of spot checking or verifying suspect piles. For smaller sites, however, static load testing may be prohibitively expensive. In such situations, dynamic load testing, originally developed for driven piles, has frequently been employed for drilled shafts and ACIP piles. In the latter case special consideration must be given to the ACIP pile slenderness and their often relatively low concrete design strength, which may not tolerate high dynamic loading stresses even though their unit resistance along the shaft is relatively high. Lately, the dynamic load test has become more feasible with the availability of loading systems that are custom tailored to this particular pile type. These systems produce a low velocity, low stress and high energy impact. Recent developments have also made the instrumentation process simpler: force measurements are now made on the ram rather than on the pile for increased reliability and simplicity. This presentation describes the requirements for successful dynamic load testing of auger cast piles and summarizes results from several projects where the new loading system and newly developed instrumentation was employed. A few cases are presented correlating static load test results with dynamic predictions, calculated by CAPWAP®.

Jan 1, 2001

By Kessi E. Zicko, Eric A. Hackenberg, Paul J. Lewis

"Following snow melt and spring rains in 2011, a landslide measuring approximately 600 feet long and 300 feet in slope length occurred within the southbound roadway embankment of a heavily travelled 2-lane divided highway in North Central Pennsylvania. Driven steel piles were designed to stabilize the embankment slope. Factors affecting the selected stabilization technique included an adjacent reservoir, wetlands, the length and depth of the failure plane, extent of glacial lake deposits, excess pore pressures in the foundation soils, and an area of archaeological interest. Field reconnaissance and subsurface explorations including borings, instrumentation, geophysics, and laboratory testing indicated that glacial lake deposits were present in the toe region of the embankment. Instrumentation proved key in measuring excess pore pressures and in locating the failure plane, and geophysics was utilized to estimate the extent of the soft glacial lake deposits and to estimate pile lengths. The existing condition of the embankment was modeled in computer slope stability analyses, which were also used to help assign soil parameters. Significant costs were associated with constructing a berm due to the impacts on adjacent site features. Therefore, multiple rows of driven steel H-piles were designed for installation along the toe of the embankment. The design lateral load in the piles was based on slope stability analyses, and the pile size and number of piles were based on lateral pile computations with modified p-y curves to account for installing piles in an active landslide. The relationship between the factors of safety from slope stability and the LRFD pile design was significant in determining pile loads for lateral analyses.INTRODUCTIONA landslide developed along the lower portion of the southbound embankment of State Route 15 in Tioga County, Pennsylvania. The road passes through a steep valley and is located along the southern extent of the Tioga Reservoir. Although no damage to S.R. 15 was attributed to this landslide, the close proximity of the slide to the road posed a concern for the long-term stability of this section of roadway.This paper presents a summary of the site history; the subsurface conditions based on borings, instrumentation, a geophysical survey, and laboratory testing; slope stability analyses including alternatives assessment; and the pile design.SITE HISTORYS.R. 15 was originally located in the valley along the Tioga River and traversed through the towns of Tioga and Mansfield. Although the reason is unknown, it is interesting to note that Old S.R. 15 curved away from the river in the area of the landslide. In the mid 1970’s, S.R. 15 was relocated to the eastern hillside prior to construction of the Tioga-Hammond Reservoir by the U.S. Army Corps of Engineers. The relocated highway was constructed in stages. Two lanes of relocated S.R. 15 were initially constructed to carry one lane of northbound and one lane of southbound traffic. At this same time, the majority of the fill was placed for two future lanes immediately to the west, which would eventually allow for two lanes in each direction. The two eastern lanes would then carry northbound traffic after completion of the two southbound lanes to the west."

Jan 1, 2015

By Daiki Takano, Naoki Takahashi, Hidenori Takahashi, Ikuo Towhata, Yoshiyuki Morikawa

"The method in this study, in which cement-treated piles are installed into the ground to decrease the amount of liquefied lateral flow, has been studied. The authors are also investigating the most effective arrangement of piles to optimize cost-effectiveness. In their investigation, they propose shifting the position of the piles to prevent lateral flow in various directions. The present study conducted centrifuge model tests to clarify the improvement effect of piles against the lateral flow of liquefied soil and the effect of the pile arrangement. Then, numerical fluid analyses were conducted to consider the improvement mechanism. As a result, the model tests and numerical analyses showed that the pile improvement dramatically reduced the lateral displacement and that the average total flow velocity decreased in the irregular case.INTRODUCTIONLiquefied ground subjected to seismic motion loses its stiffness and strength, and lateral flow often occurs in sloping areas and backfill areas behind collapsed quay walls. In the Hyogoken–Nanbu Earthquake in 1995, the reclaimed island that was surrounded by collapsed quay walls expanded toward the sea and the amount of displacement reached a few metres (Hamada et al., 1996). Two countermeasures can be considered to guard against lateral flow: preventing liquefaction and reducing lateral displacement. The former method is ideal; however it is costly and time-consuming. Based on these considerations, the authors (Takahashi et al., 2013; Morikawa et al., 2014) are currently studying a method in which cement-treated piles are installed into the ground (see Fig. 1) to decrease the amount of liquefied lateral flow. The countermeasure cost using this method is relatively low because of the low replacement ratio. The authors are also investigating the most effective arrangement of piles to optimize cost-effectiveness. It has been proposed that the position of the piles should be shifted so that lateral flow can be prevented in various directions, as described in Fig. 2."

Jan 1, 2015

By John Davie

We used a Remtek survey in Glenrock and had very good luck with it when we first started the initial investigation. We would have loved to have used that more but my understanding is the equipment is hard to find. It also requires a flooded mine workings. If you're in a dry mine the communication between the two holes is not quite as successful.

Feb 10, 2003

By Naim Noori Samie

Lateral force rsistance of piles is analytically investigated by dividing the pile length to 3 segments. The first segment (Zone I) models the load eccentricity with respect to the soil and the pile-deck connection, using a third degree differential equation representing the shear variation along the pile. The soil is assumed to be uniform, homogeneous with an elastic-perfectly plastic behavior. The Top soil layer (Zone II) is assumed to be stressed beyond the elastic limit. A simple 4th degree differential equation represents this zone. The soil resistance is assumed to vary linearly with depth (or surcharge). The pile deformation and soil behavior determines the plastic zone length. In zone III the soil is assumed to behave elastically, hence its resistance is proportional to its deformation. A linear 4th degree differential equation is employed in this zone. The compatibility conditions are satisfied on each boundary. Maximum allowable moment and shear are investigated throughout the pile as the basic limiting criteria on lateral force capacity. In this paper the soil coefficients are taken from a proposal by ref(3), and the results are compared with the soil response as determined by the P-Y method as recommended by ref(2).

Jan 1, 1996

By Kyle L. Murrell

Along the southeast United States coast, clayey silt and silty clay marine formations may cause pile installation and integrity problems. More specifically, excess pore pressures which develop in these soils during driving can cause high displacement piles to rebound or ?bounce?. Bounce is defined as a large (¾-in. to more than 1-in.) downward pile displacement during the hammer blow with little to no net displacement at the end of the blow. Pile bounce can generate damaging tension stresses and result in inefficient pile installation. A case history is presented where pile bounce was observed during the installation of 20-in. square ?high displacement? prestressed concrete piles which support a new ferry terminal in coastal North Carolina. High-strain dynamic pile testing was performed during test pile installation to evaluate driving stresses, pile capacities, and hammer performance. During and after installation of numerous production piles, circumferential cracking was observed on some of the piles. Additional high-strain dynamic pile testing was performed on two piles installed with a hammer having a heavier ram than the initial hammer. The new driving system generated lower tension stresses and installed the 20-in. piles more efficiently. Low-strain integrity testing was performed on the piles to qualitatively assess the cracks and locate any unidentified cracks. The low-strain testing was performed on piles installed at least a week prior to testing and on piles installed immediately prior to testing. When low-strain testing was performed immediately after pile installation before dissipation of excess pore pressures, pile integrity could be evaluated to depths of at least 12 pile diameters deeper than when performed weeks after installation.

Jan 1, 2008

By Hitoshi Ogura, Koichi Kobayashi, Sadao Yabuuchi

"In Japan, most pile foundations using pre-cast concrete piles are installed by the bored pre-cast piling method, wherein pre-cast piles are installed in holes that have been excavated beforehand and filled with cement milk (term used for cement water slurry in Japan). The bored pre-cast piling method with enlarged base, in which the portion near the toe is enlarged during boring operation, is widely used because of the cost benefits and the increased vertical bearing capacity that this method offers.The EX MEGATOP method, further developed as an improved bored pre-cast piling method with enlarged base, is reported here. The features of this method are: (1) High vertical bearing capacity; (2) High degree of freedom in design; (3) Excellent workability; and (4) Friendly to the environment. In particular, high vertical bearing capacity can be obtained using nodular piles and by enlarging the area at the pile toe and shaft. This method can gave a vertical bearing capacity coefficient at the toe of a=430, more than twice the corresponding value of a = 200 of a conventional bored pre-cast pile. Moreover, the shaft resistance can be several times larger than that of a conventional bored pre-cast pile. This report gives an overview of the EX MEGATOP method, evaluation of vertical bearing capacity, and examples of application of the method.1.lntroductionMost pile foundations in Japan are installed by the bored pre-cast piling method, that is, in holes that have been excavated beforehand and filled with cement water slurry, referred to as 'cement milk'. The ""bored pre-cast piling method with enlarged base"" is frequently used. In this method an enlarged excavation is used near the pile toe to increase the vertical bearing capacity.The EX MEGATOP method is a variation of the bored pre-cast piling method. Its features include the use of nodular piles and a long, enlarged excavation. The vertical bearing capacity of the EX MEGATOP method is described in this report."

Jan 1, 2005