Journal of Geotechnical and Geoenvironmental Engineering

This paper examines seven case histories of load tests on piles or drilled shafts under lateral load. Since the current design software to estimate lateral load resistance of deep foundations requires $p-y$ curves. The first approach used was correlative whereby soil parameters determined from in situ tests [standard penetration test (SPT) and cone penetration test (CPT)] were used as input values for standard $p-y$ curves. In the second approach $p-y$ curves were calculated directly from the stress deformation data measured in dilatometer (DMT) and cone pressuremeter tests. The correlative evaluation revealed that, on the average, predictions based upon the SPT were conservative for all loading levels, and using parameters from the CPT best predicted field behavior. Typically, predictions were conservative, except at the maximum load. Since traditionally SPT and CPT correlation-based $p-y$ curves are for “sands” or “clays,” this study suggests that silts, silty sands, and clayey sands should use cohesive $p-y$ curves. For the directly calculated curves, DMT derived $p-y$ curves predict well at low lateral loads, but at higher load levels the predictions become unconservative. $p-y$ curves derived from pressuremeter tests predicted well for both “sands” and “clays” where pore pressures are not anticipated.

Sinkholes are surface depressions or shafts resulting from the collapse of a submerged cavity in soil. The cavities that lead to sinkholes form as a result of underlying geology in limestone areas, or as a result of human activity such as mining or leakage from a sewer. The formation of sinkholes is often sudden and can lead to extensive damage and loss of life, especially in urban areas. Much of the literature on the subject of sinkhole formation is empirical in nature, often being associated with specific locations. This paper presents the results of a study, using numerical modeling, of the undrained stability of the submerged cavities that lead to sinkhole formation. Finite-element limit analysis techniques (using programs developed at the University of Newcastle) are used to obtain upper and lower bound values of a suitable load parameter, which bracket the exact solution. The results are compared to analytical solutions, both from literature and derived independently.

Modeled rockfill materials consisting of rounded and angular particles obtained from two dam sites are subjected to drained triaxial tests using large size specimens. An elastoplastic constitutive model based on the disturbed state concept is adopted to characterize the behavior of the modeled rockfill materials. The material parameters for the two rockfill materials are determined from the experimental results. The variation of the material parameters with respect to the size of the particles for the rockfill material with the rounded particle is, in general, opposite to that for the rockfill material with the angular particles. The model is shown to provide satisfactory prediction of the behavior of the rockfill materials tested. Material parameters are predicted for prototype size of rockfill materials.

Asphalt concrete has been used for low permeability barriers in numerous applications over many centuries. In recent times, asphalt concrete barriers have been used for waste containment applications. The hydraulic conductivity of asphalt concrete specimens can be measured in the laboratory; however, there is no expedient, efficient way of accurately measuring the in situ hydraulic conductivity of low permeability asphalt concrete shortly after its placement and compaction in the field. A method has been developed to efficiently check the in situ hydraulic conductivity of asphalt concrete in the field. Asphalt concrete specimens with varying asphalt cement contents and unit weights were prepared in the laboratory and their hydraulic conductivity measured. The measured hydraulic conductivity data were grouped into different ranges and plotted as a function of unit weight and asphalt cement content. An acceptable zone was specified for a combination of asphalt cement content and unit weight that resulted in a specified hydraulic conductivity. In the field, a quality control inspector can check the unit weight and asphalt cement content of the in-place barrier to make sure it lies within the acceptable zone. The asphalt cement content and unit weight can be readily measured, thereby allowing rapid acceptance or rejection of the asphalt concrete barrier shortly after compaction.

Cellular structures constructed of interlocking steel sheet piles are used in marine environments as cofferdams, bulkheads, mooring dolphins, and lock guide walls. In addition to providing safety against sliding, bearing failure, overturning, and tilting, cellular structures must also be designed to prevent sheet pile interlock rupture, which can lead to catastrophic failure if the cell fill is lost. Methods commonly used to estimate sheet pile interlock tensions were developed in the 1940’s, 1950’s, and 1970’s. These methods are based on empirical observations, and they do not explicitly account for soil–structure interactions. This paper presents the results of finite element analyses and instrumentation measurements performed to examine soil–structure interaction effects on sheet pile tensions. The finite-element analyses were used to compute sheet pile tensions at five instrumented cells, and the results are compared with measurements. The calibrated finite-element model was then used to investigate the effects of varying cell geometry, interlock behavior, sheet pile penetration depth, and foundation stiffness on sheet pile tensions. The instrumentation measurements provide data for estimating changes in sheet pile tensions due to cell fill densification, cofferdam unwatering, and bulkhead backfilling.

This paper presents the results of a study on the effect of pile diameter on the initial modulus of subgrade reaction. A series of ambient and impact vibration tests were performed on four different diameters of cast-in-drilled-hole piles to determine the natural frequencies and damping of the soil-pile systems. The measured natural frequencies were then compared with those estimated from a numerical model. The soil springs in the numerical model were established by implementing two different concepts on initial modulus of subgrade reaction. One is based on Terzaghi’s concept in which the modulus of subgrade reaction is independent of pile diameter. The other was based on recent research suggesting that the initial modulus of subgrade reaction may be linearly proportional to pile diameter. It was found that the measured natural frequencies were in good agreement with the computed ones when the diameter-independent modulus of subgrade reaction was employed. In addition, the test results show that the damping ratio of the system varied with pile diameter from 3% for 0.4-m pile to 25% for 1.2-m pile.

Soil anchors are commonly used as foundation systems for structures that require uplift or lateral resistance. These types of structures include transmission towers, sheet pile walls, and buried pipelines. Although anchors are typically complex in shape (e.g., drag or helical anchors), many previous analyses idealize the anchor as a continuous strip under plane strain conditions. This assumption provides numerical advantages and the problem can be solved in two dimensions. In contrast to recent numerical studies, this paper applies three-dimensional numerical limit analysis to evaluate the effect of anchor shape on the pullout capacity of horizontal anchors in undrained clay. The anchor is idealized as either square, circular, or rectangular in shape. Estimates of the ultimate pullout load are obtained by using a newly developed three-dimensional numerical procedure based on a finite-element formulation of the lower bound theorem of limit analysis. This formulation assumes a perfectly plastic soil model with a Tresca yield criterion. Results are presented in the familiar form of break-out factors based on various anchor shapes and embedment depths, and are also compared with existing numerical and empirical solutions.

Compensation grouting has been attracting attention in recent years to control ground settlement caused by underground construction. A successful and effective application of compensation grouting depends not only on the use of a good monitoring system in the field but also on a fundamental understanding of grout behavior in soils. For compensation grouting in clay, there is a need to consider the long-term effectiveness of compensation grouting. Grout injection tests were conducted in the laboratory to examine soil fracturing patterns and consolidation effects in relation to compensation grouting. Both compaction and hydrofracturing modes of grouting were tested on kaolin clay specimens with different overconsolidation ratios. Finite-element analysis was also conducted to simulate the balloon expansion tests (ideal compaction grouting tests) and the results were compared with the data from the laboratory tests. Based on the research findings, new design criteria are proposed to improve the long-term efficiency of compensation grouting for clays.

This paper presents the results of an experimental investigation undertaken to evaluate different purging solutions to enhance the removal of multiple heavy metals, particularly chromium, nickel, and cadmium, from a low buffering clay, specifically kaolin, during electrokinetic remediation. Experiments were conducted on kaolin spiked with Cr(VI), Ni(II), and Cd(II) in concentrations of 1,000, 500, and 250 mg/kg, respectively, which simulate typical electroplating waste contamination. A total of five different tests were performed to investigate the effect of different electrode purging solutions on the electrokinetic remedial efficiency. A constant DC voltage gradient of 1 V/cm was applied for all the tests. The removal of heavy metals from the soil using tap water as the purging solution was very low. When 1 M acetic acid was used as the purging solution in the cathode, the removal of chromium, nickel, and cadmium was increased to 20, 19, and 13%, respectively. Using 0.1 M ethylene diamine tetraacetic acid as the purging solution in the cathode, 83% of the initial Cr was removed; however, the nickel and cadmium removal was very low. A sequentially enhanced electrokinetic remediation approach involving the use of water as a purging solution at both the anode and cathode initially, followed by the use of acetic acid as the cathode purging solution and a NaOH alkaline solution as the anode purging solution was tested. This sequential approach resulted in a maximum removal of chromium, nickel, and cadmium of 68–71, 71–73, and 87–94%, respectively. This study shows that the sequential use of appropriate electrode purging solutions, rather than a single electrode purging solution, is necessary to remediate multiple heavy metals in soils using electrokinetics.

The undrained stress–deformation behavior of clays is significantly affected by the loading rate. Based on the observed experimental response, it is possible to model the strain rate response of clays as an apparent overconsolidated clay response. In this work, we have quantitatively determined the change in the overconsolidation ratio (OCR) due to a change in the strain rate. Our results show that the shear strength response and the excess pore water pressure response at the peak stress provide quantitatively similar magnitudes of change in the OCR with increasing strain rate. This finding holds true for both normally and overconsolidated clays. This suggests that the relationship between strain rate and change in the OCR can be considered as an inherent material characteristic and is quantifiable. A relationship between the change in the OCR and change in the strain rate is described.