bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apparatus and Procedures for Assessing Inorganic Diffusion Coefficients for Geosynthetic Clay Liners
Authors: Rowe RK , Lake CB , Petrov RJ 
Published: February 2009

Abstract
The apparatus and procedure for performing tests to obtain inorganic diffusion coefficients for Geosynthetic Clay Liners (GCLs) are described, and the processes (diffusion, anion exclusion and osmosis) that can affect the interpretation of these tests are discussed. Results from several inorganic diffusion tests on GCL and bentonite specimens show that the diffusion coefficients deduced for sodium (Na+) and chloride (Cl−) are directly related to the final bentonite void ratio. It is shown that diffusion through GCLs (or thin bentonite layers) can be modeled using a bulk porous media diffusion coefficient (Dp) consisting of the total porosity, nt, and a deduced diffusion coefficient, Dt, (Dp = ntDt) without the need to establish the true effective diffusion coefficient () without the need to establish the true effective diffusion coefficient (De) and effective porosity (ne). However, for a longer bentonite plug sample it is shown that the true effective diffusion coefficient (De) and effective porosity (ne) must be established to predict the contaminant transport through the sample.
The Physicochemical Interaction Between PHPA Polymer Slurry and Cement Mortar
Authors: Ata A , O'Neill M 
Published: February 2009

Abstract
The aim of the present study was to improve understanding of the interaction of drilled shaft concrete, polymer slurry (used to stabilize boreholes during construction of the drilled shaft), and the foundation soil. Interface shear tests were performed in the laboratory to investigate the shear resistance between soil and a cement mortar interface after exposing the interface to a high-molecular-weight polymer slurry. Two types of soils were investigated: (a) stiff silty clay and (b) medium-dense sand. Results showed that for curing periods of 7 days the interface shear resistance was 28% to 46% higher when the interface was exposed to the polymer slurry relative to the interface shear strength of the standard unexposed samples. The ability of the polymer slurry to penetrate and stretch through the pores of silty clay and dense sand soils was demonstrated by investigating the exposed soil masses using scanning electron microscopy (SEM). Exposing the outside surface of cement mortar specimens to the polymer slurry for a period of 14 days caused pitting (roughening) of the mortar surface, which explains the increased interface shear resistance between the soil and the cement mortar after exposure to polymer slurry. The laboratory behavior was verified with full-scale field tests.
Assessment of Localized Deformations in Sand Using X-Ray Computed Tomography
Authors: Alshibli KA , Sture S , Costes NC , Frank ML , Lankton MR , Batiste SN , Swanson RA 
Published: February 2009

Abstract
The internal fabric and localized deformation patterns of triaxial sand specimens were investigated using computed tomography (CT). Three displacement-controlled, conventional, drained axisymmetric (triaxial) experiments were conducted on dry Ottawa sand specimens at very low effective confining stresses (0.05, 0.52, and 1.30 kPa) in a microgravity environment aboard the Space Shuttle during the NASA STS-79 mission. CT scanning was performed on these flight specimens, as well as on an uncompressed specimen and a specimen tested in a terrestrial laboratory at 1.30 kPa effective confining stress. CT demonstrated high accuracy in detecting specimen inhomogeneity and localization patterns. Formation of deformation patters is dependent on the effective confining stress and gravity. Multiple symmetrical radial shear bands were observed in the specimens tested in a microgravity environment. In the axial direction, two major conical surfaces were developed. Nonsymmetrical spatial deformation was observed in the 1-G specimen. Analysis tools were developed to quantify the spatial density change. Void ratio variation within and outside the shear bands is calculated and discussed.
Estimation of Post-Driving Residual Stresses Along Driven Piles in Sand
Authors: Alawneh AS , Husein Malkawi AI 
Published: February 2009

Abstract
Based on both field data collected from engineering literature and measurements made using model piles, a correlation for the residual pressure at the pile tip point is presented. The resulting correlation suggested that pile flexibility is a key parameter controlling the magnitude of the residual point pressure, qres. The calculated residual point pressure values for the database piles using the developed correlation were compared with the measured values and with those calculated using Briaud and Tucker's (1984) method. The comparison indicated that predictions made using the proposed method were closer to the measurements than those obtained using Briaud and Tucker's (1984) method.
In the present study, the residual load distribution along the lower portion of the pile (the bottom 10m) was modeled as a parabola. In the upper portion of the pile, and upon the removal of the driving force, it is assumed that the upward movement of the pile is enough to reverse the direction of the unit shaft resistance from an upward direction during driving to a downward direction, with a magnitude controlled by pile flexibility as well as the available shaft friction along the upper portion of the pile. As a consequence of this approach of modeling residual load distribution, the results indicate that residual load distribution peaks at a distance (less than 0.3L) above the pile tip point. This distance (measured from the pile tip) decreases with increasing pile flexibility, and for flexible pile, residual shear stresses may act in the downward direction all the way down to the pile tip. Also, the method of analysis adopted in this paper indicates that in some cases the magnitude of the peak residual load may exceed 50% of the measured ultimate uplift load. This magnitude is significant and leads to the prudent conclusion that any design method for an axially loaded pile in sand using pile load test data as a database should consider the existence of residual loads when pile load test data are interpreted.
Performance of Drilled Shafts with Isolation Tubes in an Expansive Environment
Authors: Kim M-H , O'Neill MW , Kramer SL 
Published: February 2009

Abstract
An experimental study that included detailed observation of four 305-mm-diameter test shafts, one reference shaft of standard design, and three test shafts with isolation tubes to mitigate skin friction in the vadose zone, is described. The shafts were loaded by naturally expanding and contracting soil over a period of 17 months. The soil at the test site was instrumented to track suction changes to permit development of a computational model predicting soil heave and shrinkage that occur during suction changes at the field site.
Maximum ground movements exceeding 35 mm were observed. Movements of only 1 to 2 mm were observed in the test shafts with isolation tubes, while movements of 4 to 5 mm were observed in the reference shaft. Tension forces in the shafts protected by the isolation tubes were minimal compared to those measured in the reference shaft.
A simple computational model was developed to predict the maximum amount of ground heave based on suction changes. A relationship among suction, total stress, and volumetric strain was obtained for the soil at the test site in the laboratory. This relationship, used as inputs to the predictive model, enabled the computation of the maximum ground heave. Such a model can be used to ascertain whether isolation tubes may be indicated.
A Method for Testing Tensile Strength in Unsaturated Soils
Authors: Tang GX , Graham J 
Published: February 2009

Abstract
This paper presents a new method for testing tensile strength in unsaturated soils. A rigid tensile mold has been designed and simple testing procedures developed. A series of tension tests has been carried out on densely compacted unsaturated soil specimens to evaluate the method. The material tested in this study was a highly plastic 50:50 (by dry weight) mixture of sand and Na-rich bentonite. Cylindrical specimens were the same size and shape as those used for triaxial tests.
Effects of Calcium Sulfate on Swelling Potential of an Expansive Clay
Authors: Azam S , Abduljauwad SN , Al-Shayea NA , Baghabra Al-Amoudi OS 
Published: February 2009

Abstract
The unique chemical features of calcium sulfate are largely manifested by its phase transformation due to the reversible hydration-dehydration reaction. Due to the harsh climatic and environmental conditions in eastern Saudi Arabia, such phase changes add to the potential swelling hazards of local expansive clays. The adsorption of water by expansive soils and the hydration of anhydrite to gypsum are the sources of much damage to foundations throughout the world. This paper attempts to assess the swelling caused by the interaction of calcium sulfate phases, especially gypsum and anhydrite, with expansive clay. Such assessment was primarily based on studying the geotechnical, mineralogical, and volume change characteristics of calcium sulfate-bearing soils. X-ray and thermal analyses were used to estimate the type and amount of minerals during phase transformation of calcium sulfate. The swelling potential was determined using an improved version of the simple odometer and constant-volume tests. The conventional odometer is the device usually used in these tests. However, the size of soil samples, the complete confinement, and the rigidity of the conventional odometer imposes a serious limitation on the application of the laboratory results to actual field problems. Therefore, the authors investigated the use of a large-scale odometer with different mold sizes and shapes on the swelling potential of some mixtures of expansive clay and calcium sulfate phases. In addition, the soil fabric of these mixtures was investigated using scanning electron microscopy to explain the volume change behavior. The results of this investigation indicated that the swelling potential of clay-calcium sulfate mixtures decreased as the percentage of calcium sulfate was increased, and this reduction was more pronounced when gypsum was used. Swelling pressure was observed to be the highest in the conventional odometer and lowest in the large-scale square odometer mold.
New Tool for Shear Wave Velocity Measurements in Model Tests
Authors: Arulnathan R , Boulanger RW , Kutter BL , Sluis WK 
Published: February 2009

Abstract
A method for measuring the shear wave velocity (Vs) of soil in a centrifuge model using a “mini-air hammer” is presented. Propagation of shear waves in a model soil profile was recorded in-flight by a vertical array of four accelerometers placed at different depths. Shear wave velocities were measured at different centrifugal accelerations for Nevada sand and for peaty organic soil. The Vs measured in the centrifuge was in excellent agreement with the Vs measured using piezo-ceramic bender element tests on these soils in a triaxial device. The value of the Vs measurements is demonstrated by typical analysis results for a centrifuge model of horizontally layered peaty organic soil and Nevada sand subjected to simulated earthquake shaking. Site response analyses using the measured shear wave velocities as input parameters produced good agreement with the measured site response.
Tomographic Detection of Low-Velocity Anomalies with Limited Data Sets (Velocity and Attenuation)
Authors: Prada J , Fratta D , Santamarina JC 
Published: February 2009

Abstract
Inherent physical difficulties associated with the effect of low-velocity anomalies on wave propagation, limited data sets, and restricted illumination angles affect the tomographic assessment of piles, caissons, slurry walls, and other similar geotechnical systems. This study evaluates various inversion methodologies for the tomographic detection of low-velocity anomalies. Travel time and amplitude data are gathered in the laboratory by simulating realistic field conditions. The inversion methodology involves data preprocessing, fuzzy logic constraining, and various forms of tomographic inversion based on either pixel or parametric representations of the medium. It is shown that the tradeoff between variance and resolution in pixel-based inversions can be overcome by adding information, such as regularized solutions, or by capturing the problem in parametric form for a presumed simple geometry. Results show that amplitude-based inversion may be more advantageous than time-based inversion in the detection of low-velocity anomalies; however, consistent coupling of transducers is required. The most robust inversion method tested in this study for the detection of low-velocity anomalies under standard field situations (i.e., limited data and restricted illumination angles) involves a combination of fuzzy logic constraining followed by parametric-based inversion.
The Accuracy of Hydrometer Analysis for Fine-Grained Clay Particles
Authors: Lu N , Ristow GH , Likos WJ 
Published: February 2009

Abstract
This paper provides a rigorous analysis on the accuracy of Stokes' equation for calculating particle-size distributions of nonspherical, fine-grained clay particles. Analytical expressions relating the actual particle shape and size to the equivalent “Stokes' diameter” are presented for disk-shaped and rod-shaped particles. Disks and rods are chosen to represent the high aspect ratios typically exhibited by real clay particles. For particle sizes ranging from 0.1 µm to 100 µm and for aspect ratios ranging from 10 to 500, it is shown that Stokes' equation underestimates the maximum particle dimension by up to two orders of magnitude. Consequently, particle-size distributions calculated from conventional hydrometer analysis are shown to be misleading. To confirm the contention that Stokes' equation may not be appropriate for calculating particle sizes and particle-size distributions for fine-grained clays, kaolinite and pulverized mica are characterized by comparing results from hydrometer analysis, sieve analysis, laser diffraction analysis, and scanning electron microscopy (SEM). The experimental results confirm the error estimates from the theoretical evaluation.
The Influence of Variation of Centrifugal Acceleration and Model Container Size on Accuracy of Centrifuge Test
Authors: Zeng X , Lim SL 
Published: February 2009

Abstract
Centrifuge modeling has become a popular and powerful experimental tool in geotechnical engineering. The centrifugal acceleration, which is used to simulate the gravitational acceleration, varies within a model in both magnitude and direction. As a result, the stress field in a centrifuge model is different from that in the prototype being simulated. This paper presents the results of a numerical simulation of the effect of the variation in radial centrifugal acceleration on the stress distribution in a centrifuge model, and its impact on the accuracy of test results. The influence of the centrifuge radius and the size of a model container is investigated.
Determination of Surface Area of Fine-Grained Soils by the Ethylene Glycol Monoethyl Ether (EGME) Method
Authors: Cerato AB , Lutenegger AJ 
Published: February 2009

Abstract
This paper describes a test procedure for determining the total surface area of fine-grained soils using the Ethylene Glycol Monoethyl Ether (EGME). The test involves saturating a soil sample with EGME and then removing the excess EGME in a vacuum desiccator, until the EGME forms a monomolecular layer on the soil surface. The results of the test are expressed as Specific Surface Area (SSA), which describes the surface area/unit mass of dry soil with units of m2/g. Test results are presented demonstrating the effect of various test parameters on the results. Results for a number of different fine-grained soils are presented. A detailed recommended test procedure is given. The proposed method uses simple and inexpensive laboratory equipment, is relatively simple to perform, and allows for rapid determination of SSA.
Factors Affecting the Filter Paper Method for Total and Matric Suction Measurements
Authors: Leong EC , He L , Rahardjo H 
Published: February 2009

Abstract
The filter paper method is used as an indirect means of measuring soil suctions. The advantages of the method include its simplicity, its low cost, and its ability to measure a wide range of suctions. The filter paper method has also been used in the field to measure soil suctions. However, the simplicity of the filter paper method has led to an inadequate understanding of the method and, therefore, improper usage. Recent findings have highlighted the need for more precautions in the use of the filter paper method for suction measurements. This paper presents a literature review of the factors affecting the accuracy of the filter paper method and identifies gaps in the current knowledge of the method. An experimental study was also conducted to clarify some of the factors affecting the response of the two most commonly used filter papers for suction measurements. Whatman No. 42 and Schleicher and Schuell No. 589. Calibration curves of the filter papers show that the water content-suction relationships are different for total and matric suctions. The total suction calibration curve is not very sensitive to applied suctions less than 1000 kPa. The calibration curves obtained for total suction are different from those recommended in ASTM D 5298-94, suggesting that the ASTM D 5298-94 equations should not be used for total suction. Instead of existing bilinear equations, new equations are proposed to describe the total and matric suction calibration curves. All the equations were evaluated using the filter paper method to measure the suction of soil specimens of known matric suctions.
A Laboratory Study of the Hysteresis of a Thermal Conductivity Soil Suction Sensor
Authors: Feng M , Fredlund DG , Shuai F 
Published: February 2009

Abstract
An experimental program was set up to study the capillary hysteresis of the ceramic block for a newly developed thermal conductivity soil suction sensor. The testing program included two series of tests: one series of tests measured the capillary hysteresis of the ceramic blocks and the other measured the hysteresis of the relationships between the suction sensor output and the applied suctions. Test results show that there can be approximately 40% error from the correct suction value if the conventional calibration curve is used without considering the effects of capillary hysteresis. Based on the experimental testing program, a mathematical approach, which is able to take into account the effects of capillary hysteresis, was proposed when interpreting the measured soil suction data.
Interfacial Behavior of Unsaturated Soil with Small-scale Models and Use of Image Processing Techniques
Authors: Gachet P , Klubertanz G , Vulliet L , Laloui L 
Published: February 2009

Abstract
Two small-scale prototypes (physical models) intended to study soil behavior are presented. They allow for 1D and 2D tests on unsaturated soil in a wide range of hydraulic and mechanical boundary conditions. The instrumentation of the testing facilities designed to measure pore water pressures, water fluxes, top displacements, and in-plane displacement fields are detailed. Special attention is devoted to boundary conditions: effects of friction and cohesion at the interface between soil and model on the experimental results and ways to limit their effects are presented. Furthermore, the image processing techniques used to measure in-plane displacements are reviewed. A simple and accurate method based on white light speckle autocorrelation and a marked membrane is proposed.
Effect of Aging on Swelling and Swell-Shrink Behavior of a Compacted Expansive Soil
Authors: Subba Rao KS , Tripathy S 
Published: February 2009

Abstract
Effect of aging on swelling and swell-shrink behavior of a compacted expansive soil is investigated in this paper. An expansive soil having a liquid limit of 100% is used for this purpose. Compacted specimens were prepared and aged for a predetermined number of days (7, 15, 30, and 90 days) to study their swelling and swell-shrink behavior. It has been shown that aging improves the resistance to compression of compacted specimens. The swelling potentials of specimens also decreased with aging. The dominant factors that influence the aging effects are the water content and degree of saturation at the beginning of the aging process. The changed behavior of aged specimens is attributed to particle rear-rangements and formation of bonds, which affect the surface area absorbing water during swelling. The cyclic swell-shrink tests on aged specimens indicated that the differences in vertical displacement during the first swelling were eliminated in the subsequent cycles when specimens were shrunk more, but the aging effect was found to persist with cycles for specimens subjected to lower shrinkage magnitudes.
Ko-Volume Change Characteristics of an Unsaturated Soil with Respect to Various Loading Paths
Authors: Rahardjo H , Fredlund DG 
Published: February 2009

Abstract
The volume change behavior of an unsaturated soil is a function of the stress state variables; namely, net normal stress and matric suction. The total and water volume changes during drained and constant water content loadings are investigated, and their behavior is described with respect to changes in the stress state variables. Volume changes are also presented in terms of void ratio and water content changes. The differing characteristics of volume change during drained and constant water content loadings are reflected clearly through the void ratio and water content changes. The significance of the highest, past matric suction is shown to be similar to the preconsolidation pressure influence on a saturated soil. The laboratory test results show that the water coefficient of volume change changes significantly from the reloading curve to the virgin compression curve. The effect of preconsolidating the soil was also shown to influence significantly the measured soil-water characteristic curve.
Centrifuge Modeling of Tapered Piles in Sand
Authors: Sakr M , Hesham El Naggar M 
Published: February 2009

Abstract
An experimental study was performed to investigate the performance of tapered and cylindrical piles driven into loose sand using the geotechnical centrifuge located at C-CORE, Memorial University, Newfoundland. Twelve open-ended model piles with different configurations, instrumented externally along the shaft, were successfully installed and load tested using the facility. The piles were driven at 1 g, and the loading tests were conducted at 10 g. The paper discusses the design of model piles and details of loading equipment and presents the results of axial compression tests. The results obtained showed that modeling tapered and cylindrical piles with different length-to-diameter ratios was successfully achieved. The external instrumentation technique used in this study proved to be efficient. The surface ronghness effect was found to be important and must be considered when interpreting the test results. The raining technique used in this study produced reasonably uniform soil samples. It was found that as the taper angle increased the shaft resistance increased, and the shaft resistance of the tapered pile was up to 185 % larger than that of the equivalent cylindrical pile. It was also found that the values of the combined shaft resistance factor β for cylindrical piles were consistent with Canadian Foundation Engineering Manual (1992) guidelines. In the case of tapered piles, β values were found to be 80 % higher than those for cylindrical piles, whereas the CFEM design guidelines suggest they should be 30 to 50 % higher. The effect of the taper established from experimental results compared well with the results obtained from an analytical solution based on cavity expansion theory.