bluuebunny/crossref_metadata_2025 huggingface dataset:
Geotechnical Properties of Municipal Solid Waste
Authors: Gabr MA , Valero SN
Published: February 2009

A geotechnical testing program was conducted to evaluate the engineering properties of aged solid waste samples retrieved from a landfill that began accepting waste as early as 1940. The conducted tests included water content, specific gravity, Atterberg limits, grain-size distribution, compaction, permeability, consolidation, triaxial, and direct shear. Maximum dry unit weight achieved using the Standard Proctor Test was approximately 9.3 kN/m3 at a water content of 31%. Compression Index values, Cc, derived from small-scale (63.5 mm in diameter), one-dimensional consolidation tests were between 0.4 and 0.9 for a void ratio range of about 1.0 to 3.0. Secondary Compression Index values, Cα, appeared to be less dependent on initial void ratio and more dependent on conditions favorable to microbial activity and were estimated to range between 0.009 and 0.03. Total strength parameters from consolidated undrained (CU) triaxial tests yielded a range of cohesion values, c, of about 100 kPa at w of 55% to 40 kPa at w of 72%. Apparent effective strength parameters were evaluated as an effective friction angle, φ', of 34° and an effective cohesion of 16.8 kPa. Results from direct shear tests at different levels of horizontal displacement indicated that the value of the friction angle increased with the displacement level while cohesion remained essentially constant. Effective friction angles, φ', of 20.5 to 39° with c' of 27.5 to 0 kPa were evaluated from the direct shear tests. In general, results from this study were comparable to those reported in the literature and obtained from laboratory, field, and large-scale unconventional tests. However, the apparent effective strength parameters evaluated from the conventional laboratory tests seem generally higher than those evaluated through back calculations. Apparent effective friction angle values evaluated in this study were as much as 10° higher than those reported in the literature and evaluated from back calculations.
A Study of Strike-Slip Faulting Using Small-Scale Models
Authors: Lazarte CA , Bray JD
Published: February 2009

Results from tests on small-scale soft clay models subjected to strike-slip faulting in a 1-g environment are presented. Kinematic/boundary conditions and material ductility were dominant factors on model response. Material ductility significantly affected the deformation and breakage patterns in level ground and embankment models, with larger base offsets being required to produce surface offsets in ductile materials. In addition, the shear zone was broader with ductile materials. Horizontal and vertical distributions of shear deformation within the models are presented. The rate of rupture propagation appears to increase as the base fault ruptures up through the soil. The effect of model geometry and base fault orientation are also important in the model's response.
Wave Propagation in Soils: Multi-Mode, Wide-Band Testing in a Waveguide Device
Authors: Fratta D , Santamarina JC
Published: February 2009

This paper presents the development of a waveguide device and the corresponding processing methodology to study wave propagation in particulate materials. Its main advantages are: the cancellation of biasing transfer functions (e.g., transducer, coupling, and electronics); the determination of both velocity and attenuation in a wide frequency range; the evaluation of torsional, flexural, and longitudinal propagation modes; and the computation of field propagation parameters from laboratory multi-mode data. Fundamentals of signal processing are reviewed, followed by a discussion of design considerations including boundary effects and geometric dispersion. Typical results are presented.
Coupled Heat and Moisture Flow in Unsaturated Swelling Clay Barriers
Authors: Mohamed AMO , Yong RN , Onofrei CI , Kjartanson BH
Published: February 2009

The main thermodynamic forces active in the near field of a nuclear fuel waste multiple barrier system during the unsaturated stage are the gradients of temperature, fluid pressure, and chemical potentials. The processes that have a direct impact on the transport mechanism of heat and moisture within the clay-based compacted buffer material are coupled. The major problems in describing coupled heat and moisture flow (CHMF) in unsaturated swelling clay barriers are the lack of experimental data and the lack of a method to estimate CHMF diffusivity parameters (CHMF-DIPAR).

This paper presents the experimental procedures, the analysis of experimental data, and a method of determining CHMF-DIPAR. Several series of one-dimensional tests were performed to examine the transient temperature and moisture flow in buffer material compacted at a dry density of 1.67 Mg/m3 and optimum volumetric moisture content (VMC) of 0.28. CHMF-DIPAR were calculated using the measured temperature and moisture distributions combined with an analytical solution of CHMF equation and a square-root time (SQRT) technique.
High-Temperature Brazilian Test for Tensile Strength of Metamorphic Limestone
Authors: Lee D-H , Juang CH , Lei I-M
Published: February 2009

This technical note presents a low-cost and fast, high-temperature tensile strength test of rocks. A series of splitting tensile strength tests, the so-called Brazilian test, were conducted on metamorphic limestone specimens at high temperature using a special triaxial cell assembly that can sustain a maximum temperature of 315°C. Results of these Brazilian tests at various temperatures (30, 100, 200, and 300°C) are presented and discussed. The results show that the tensile strength of the rock decreases as the temperature of the rock increases. The reduction in tensile strength is found to be greater when the tests are actually conducted at high temperature rather than at room temperature using thermally treated specimens.
Grain-Size Distribution of Mixed Aggregates
Authors: Windisch ÉJ
Published: February 2009

When various aggregates are to be combined in order to obtain a mix having a desired grain-size distribution, current methods are based on a trial-and-error approach. It is shown in this paper that the process of combining various soils or aggregates may be a simple, rapid, and efficient procedure that eliminates the need for trial and error. The paper presents the formulation of the combination process as a problem of optimization and describes the steps of the proposed procedure. The solutions of some typical problems of aggregate combinations are given as examples.
Proposed Standard Test Method for Measurement of Pneumatic Permeability of Partially Saturated Porous Materials by Flowing Air
Authors: Eischens G , Swanson A
Published: February 2009

This proposed standard describes a laboratory test method for the measurement of the coefficient of permeability for airflow (pneumatic permeability) through porous media (e.g., soils) partially saturated with water. Control and measurement of the airflow is effected at the inlet of the specimen. The permeameter cell is fitted with dual transfer lines that isolate the specimen pressure drop from the effects of gas flow in the apparatus. Electronic instrumentation results in short test times that minimize changes in water content. This proposed standard addresses the need to develop a body of knowledge in support of soil vapor extraction (SVE) systems and allied environmental remediation activities.
A New Technique for Diffusion Testing of Unsaturated Soil
Authors: Barbour SL , Lim PC , Fredlund DG
Published: February 2009

A technique is proposed for determining the coefficients of diffusion and adsorption for ions in unsaturated soils. The method integrates the single reservoir diffusion testing of saturated soil with the axis-translation technique for the control of matric suction. The procedure allows for the application of a net total stress and matric suction to the soil during the diffusion test. The use of this new technique to determine the coefficients of diffusion and adsorption of ions from a single test is demonstrated. The effects of the degree of saturation on the coefficients of diffusion and adsorption were evaluated on a sandy soil with water contents ranging from saturation to near the residual degree of saturation. Potassium and chloride ions were used as the primary tracers.

The test results showed that both the coefficients of diffusion and adsorption can be determined from a single test. The results illustrate a decrease in both the effective diffusion and adsorption coefficients with a decrease in the degree of saturation. The extent of the decrease in the effective diffusion coefficient from saturation to near the residual degree of saturation was approximately 80%. The decrease in the adsorption coefficient was gradual and small from saturation to a degree of saturation of approximately 10%; however, it then decreased rapidly as the water content approached the residual degree of saturation.
Model Size Effects in Centrifuge Models of Granular Slope Instability
Authors: Goodings DJ , Gillette DR
Published: February 2009

Two assumptions behind geotechnical laboratory testing are: first, that soil with grains small enough to behave as a continuum in a full-scale field situation will also behave as a continuum in a small laboratory test; and, second, that side boundary effects in a laboratory test are either negligible or, if not negligible, do not dominate behavior but are quantifiable so that a correction can be made for their effects. Data are presented here from 61 centrifuge models of slopes brought to failure to assess side boundary and grain-size effects on model behavior. Three granular soils of different grain sizes were used to build models of different scales and widths. Model slopes were brought to failure by increasing self-weight, which simulates increasing full-scale height while maintaining slope geometry. To simulate the behavior of soil with cohesion, a small negative pore pressure was applied to the soils using a vacuum.

Models failed with wide, shallow slope failures. There were two effects on model behavior arising from grain size. First, it appears that the model failure “surface” may have to be more than 30 grain diameters below the soil surface before grain-size effects are negligible. Secondly, the repeatability of model results was also affected by grain size: coefficients of variation in failure data for a single group of identical models were 10% or less when slope height was 158 grain diameters or greater; coefficients of variation increased markedly for smaller model slopes with heights 56 grain diameters or less. When effects of model width were examined, it appears that model width may have to exceed model slope height by a factor of 5 for shallow wide slope failure to develop unimpeded by side boundaries.
Engineering Properties of Tire/Soil Mixtures as a Lightweight Fill Material
Authors: Masad E , Taha R , Ho C , Papagiannakis T
Published: February 2009

The United States Environmental Protection Agency (USEPA) estimates that over 279 million discarded tires are being added annually to the already existing stockpile of two billion tires. Current disposal and stacking methods of waste tires are not acceptable due to the possibility of fire and health hazards. Several states and the federal government have issued legislation that encourages or mandates the recycling of discarded tires. One application where shredded tires can be used is as a lightweight fill material behind retaining walls or in highway embankments over weak or compressible soils.

This paper presents the engineering properties of shredded tires, Ottawa sand, and a mixture of 50% Ottawa sand and 50% shredded tires by volume (70% Ottawa sand and 30% shredded tires by weight). The maximum size of the tire chips used was 4.75 mm. Gradation, specific gravity, void ratio, density, permeability, and consolidated-drained (CD) triaxial tests were performed as part of the testing program. Although the data obtained were limited to the above three mixes, the results indicate that the use of shredded tires/Ottawa sand mixes as a lightweight fill material is very promising. However, long-term impact of leachates from tires on groundwater quality should be investigated.
Effects of Fines on Monotonic Undrained Shear Strength of Sandy Soils
Authors: Thevanayagam S , Ravishankar K , Mohan S
Published: February 2009

Shear strength of liquefied sands is an important component in seismic slope stability evaluation. Experimental data on a host sand mixed with different amounts of fines content and a careful analysis of other available steady state strength (Sus) data show that fines content and relative density play important roles affecting Sus. Fines content is found to be the major factor affecting Sus. When the Sus data for sands are grouped into (a) relatively clean sands (<12% fines), (b) silty sands (12 to 32% fines), and (c) silts or sandy silts (>50% fines) at the same relative density, relatively clean sands show the highest Sus. Silts show the lowest Sus. Silty sands show intermediate strengths. Based on this data, lower-bound relationships are proposed for Sus as a function of Dr and fines content.
Grain-Size Distribution of Granular Soils by Computer Vision
Authors: Raschke SA , Hryciw RD
Published: February 2009

A semi-automated technique for obtaining the grain-size distribution (GSD) of granular soils using computer vision is presented. Backlighted digital images of a soil specimen dispersed over a glass specimen plate are acquired at three different magnifications. Images of the specimen are acquired by placing the specimen plate randomly beneath the field of view of a charged-coupled device (CCD) video camera. The size of particles with projected areas from 50 to 2000 pix2 is measured in each image. Multiple images are acquired at each magnification until the measured size distribution of particles counted at that magnification stabilizes. Probabilistic corrections are then used to obtain a statistically unbiased GSD from the image data obtained at all three magnifications. A comparison of GSD data for two uniform and two nonuniform soils using both computer vision and sieving is presented.
Testing of Reinforced Slopes in a Geotechnical Centrifuge
Authors: Zornberg JG , Mitchell JK , Sitar N
Published: February 2009

An evaluation of the use of centrifuge modeling as a tool for analyzing the behavior of reinforced soil slopes is presented in this paper. A review of the state-of-the-art indicates that previous centrifuge studies have focused mainly on the performance of reinforced soil vertical walls and that limit equilibrium approaches (used in the design of reinforced soil slopes) have not been fully validated against the failure of models in a centrifuge. As part of an evaluation of the conditions of similarity governing the behavior of reinforced soil structures at failure, scaling laws are specifically derived by assuming the validity of limit equilibrium. It is demonstrated that an Nthscale reinforced slope model should be built using planar reinforcements having 1/N the strength of the prototype reinforcements in order to satisfy similarity requirements. A description of the experimental testing procedures implemented as part of a recent centrifuge testing program is presented, and an example dataset from this investigation is used to illustrate typical results. These include the g-level at failure, visual observation of failure development, and post-failure analysis of reinforcement breakage. The pattern observed in the geotextile reinforcements retrieved after testing indicates that the boundary effects were negligible.
Measurement of the Contact Angle of Water on Geotextile Fibers
Authors: Henry KS , Patton S
Published: February 2009

The contact angle of water on geotextile fibers significantly influences capillary behavior. Measurements of the dynamic contact angle of tap water on geotextile fibers are reported for two geotextiles, as received from the manufacturer and after they had been treated (cleaned). There is considerable hysteresis between advancing and receding contact angles, as expected. Fibers from one geotextile have significantly lower contact angle cosines than the other, indicating that it is less wettable. The cleaning of geotextiles resulted in significant reduction in the advancing contact angles of fibers from one of the geotextiles but not the other. The heights of water capillary rise in strips of the geotextiles were also measured. Results showed that the contact angle measurements are helpful; but, information on pore sizes is also needed to predict capillary behavior.
Interpretation of Model Pressuremeter Test Using Automated Clay Calibration Chamber Data
Authors: Penumadu D , Chameau J-L
Published: February 2009

The details of an automated flexible wall calibration chamber test system developed to perform strain-controlled model pressuremeter testing in cohesive soil are presented. The procedure involved in obtaining uniform speciments by consolidating a slurry of kaolin in two stages is described. The importance of automated control (electro-pneumatic control for this study) to perform second stage K0 consolidation accurately is shown. Typical test results are presented along with the evaluation of undrained strength, initial shear modulus, stress-strain variation, limit pressure, and horizontal stress using various methods of interpretation. Unload-reload loops were performed, and the shear modulus values were compared with the deduced values from the initial loading curve. Interpreting the pressuremeter test data using the Marquardt-Levenburg algorithm is presented. The improvements to the Simplex method are identified along with the effect of the reference state. A new procedure for incorporating the unloading portion in interpreting the pressuremeter test data is developed along with the detailed comparisons.
Computer Vision-Based Technique to Measure Displacement in Selected Soil Tests
Authors: Obaidat MT , Attom MF
Published: February 2009

The potential of normal case photography using charge-coupled-device (CCD) cameras to extract deformation (strain) in soil specimens of two soil tests, i.e., the unconfined compression test and the direct shear test, was investigated. A PC-based digital vision system was used to obtain accurately measured linear displacement. Using remolded soil specimens, comparisons between displacement measurements using ASTM conventional methods and the normal case photography method showed that use of the latter method is promising and could be used as a substitute for strain gages. Experimental investigation showed that differences between displacement measurements using conventional ASTM procedures and computer vision technique were consistently within 0.04 ± 0.15 to 0.3 ± 0.23 mm for unconfined compression tests and direct shear tests, respectively. This was compatible with the image scale where one pixel on the image domain was equivalent to about 0.4 mm on object space coordinates. Statistical correlations between strains by the two methods supported this result. Image scale and resolution were found to be the two major factors affecting the accuracy of the measurements. The results of this work are expected to open the door for geotechnical engineers and agencies responsible for soil testing standards to incorporate image-based analysis in soil testing. This will indeed bridge the gap between manual and fully automated soil testing measurements.
Theoretical Evaluation of the Transient Response of Constant Head and Constant Flow-Rate Permeability Tests
Authors: Zhang M , Takahashi M , Morin RH , Esaki T
Published: February 2009

A theoretical analysis is presented that compares the response characteristics of the constant head and the constant flow-rate (flow pump) laboratory techniques for quantifying the hydraulic properties of geologic materials having permeabilities less than 10−10 m/s. Rigorous analytical solutions that describe the transient distributions of hydraulic gradient within a specimen are developed, and equations are derived for each method. Expressions simulating the inflow and outflow rates across the specimen boundaries during a constant-head permeability test are also presented. These solutions illustrate the advantages and disadvantages of each method, including insights into measurement accuracy and the validity of using Darcy's law under certain conditions. The resulting observations offer practical considerations in the selection of an appropriate laboratory test method for the reliable measurement of permeability in low-permeability geologic materials.
Design of Polyvinyl Chloride Tar Mixes for Resistance to Permanent Deformation
Authors: Singh G , Dhliwayo MW
Published: February 2009

The problem of shortages of normally acceptable materials can be alleviated by using low- and marginal-quality materials through selective use of stabilization. In areas where coal is prevalent coke-oven tar, modified with small quantities of polyvinyl chloride (PVC), can be mixed with sand to produce good paving material. Static and dynamic tests performed on PVC tar-sand mixtures show that the addition of PVC produces vast improvements in the Marshall properties and the resistance to permanent deformation, with only marginal influence on the compatibility. Mix design based on repeated loading tests at various temperatures suggests that the addition of PVC reduces the optimum binder content.
Phenomenological Study of Model Piles in Sand
Authors: Yazdanbod A , O'Neill MW , Aurora RP
Published: February 2009

A device is described whereby sand can be confined in a depthwise variable manner to permit simulation of lateral earth pressures to depths simulating driving depths of piles. Instrumented model piles were driven into a quartz sand placed at two different densities in the device, and load transfer patterns were measured for varying depths of penetration for compressive and uplift loading. In most respects the load transfer patterns were similar to those measured in full-scale tests in sand.
Measurement of Lateral Stress Around Multihelix Anchors in Sand
Authors: Clemence SP , Pepe FD
Published: February 2009

The lateral stress regime around a one-quarter scale model triple-helix anchor was measured with diaphragm-type soil stress cells. Laboratory anchor pullout tests were run in a dry, uniformly graded sand at two different depths and relative densities. Lateral stresses were measured before and after installation of the helical anchor, at anchor failure, and continuously during the application of the uplift load. Results indicated that helical anchor installation causes increase in lateral stress around the anchor. Large increases in stress were observed in dense soils. In addition, lateral stresses increased as the anchor was loaded to failure. This behavior was attributed to arching stresses and soil dilatancy developing in the sand as it was sheared by the anchor. The magnitude of these increases was found to depend on the relative density of the sand. Based on the test results, values of the coefficient of lateral stress at failure kF were calculated for several densities and depths. The calculated kF values were found to be 30 to 40% lower than those proposed by Meyerhof and Adams for buried foundations. These lower values are due to the shearing disturbance during anchor installation.
Filter Openings Measured by a Suction Method
Authors: Dennis CW , Davies PA
Published: February 2009

A laboratory method is presented for determining the distribution of opening sizes within initially water saturated geotextiles under simulated soil loading, the principle being to measure air entry values over a range of applied suctions. Construction and use of the apparatus concerned are outlined while the analysis of data so obtained is given in detail. Results from two geotextiles are presented, and a comparison is made with data obtained by another method.
Evaluation of Schmidt Hammer Rebound Hardness Test Holders
Authors: Gunsallus KL , Kulhawy FH , O'Rourke TD
Published: February 2009

An evaluation is made of three different holders for Schmidt hammer tests on rock core in the laboratory, including steel angle, V-notch, and semicircular groove holders. The differences are small, but it is shown that the V-notch holder gives consistently higher rebound hardness values. It is also easier and more economical to build. These qualities indicate that the V-notch holder would be a better selection for conventional use.
Laboratory Evaluation of Soil Suction Components
Authors: Edil TB , Motan SE
Published: February 2009

A laboratory evaluation of the soil-water potential components (total, matrix, and osmotic suction) is presented using a series of clay specimens statically compacted dry- and wet-of-optimum. In unsaturated soils, moisture movement is controlled either by total or matrix suction depending upon the degree of unsaturation, whereas deformation and strength behavior is controlled primarily by matrix suction. Therefore, it is imperative to evaluate the suction components separately. Significant osmotic suction component was induced as a result of incomplete leaching of the sodium and calcium surface-saturated Grundite (initially prepared by treating the clay slurry with strong sodium chloride and calcium chloride solutions to achieve mass action of cations). Matrix suction was induced by equilibrating the specimens to different pressures on a ceramic-plated extractor. At equilibrium, total suction of the specimens was measured using a Peltier type psychrometer. Test results indicate the use and limitations of the psychrometric method and the interrelationship of suction components. Measured values of the total suction by the psychrometric method indicate more consistent results at moisture contents above the plastic limit. Below the plastic limit, the osmotic component, as deduced by the difference between total and induced matrix suctions, tends to decrease gradually with increasing matrix suction. It is found that the osmotic suction can be measured most suitably on pore-water extracts using psychrometry.
Suggested Method for Estimating the In-Situ Modulus of Deformation of Rock Using the NX-Borehole Jack
Authors: Heuze FE
Published: February 2009

The NX-borehole jack is a widely used tool for estimating the deformability of rock masses in-situ. It applies unidirectional pressure to the walls of a rock borehole by means of two steel platens. In theory, the analysis of test data is straightforward: the modulus estimate requires a record of applied hydraulic pressure versus borehole diameter change, and a knowledge of the rock's Poisson's ratio. In practice, the above procedure, using the original theoretical formula, frequently has resulted in computing a material modulus that was demonstrably too low.

Today, it is finally understood how one or more of the following factors can provide a low modulus estimate: (1) the longitudinal outward bending of the jack plates which gives artificially high readings of the displacement gages and (2) the mismatch between borehole and jack platen radii, which would negate the full platen/rock contact assumed in the original analysis, and (3) tensile cracking of the intact rock or tensile opening of natural joints around the borehole under the jack.

The detailed discussion of the theoretical developments is contained in a separate paper, which should be a complement to this draft. This document outlines a suggested procedure for testing with the NX-jack, and analyzing the test results in a medium which is assumed to be isotropic, linear, clastic, and homogeneous.
A Direct Tensile Loading Apparatus Combined with a Cubical Test Cell for Testing Rocks and Concrete
Authors: Meier RW , Ko H-Y , Sture S
Published: February 2009

A novel tensile loading apparatus is described, which when used in conjunction with an existing fluid-cushion cubical test cell, allows the simultaneous application of a pure principal tensile stress and transverse principal compressive stresses to concrete and rock specimens with a minimum of boundary constraints. A tensile stress is applied along one axis of a cubical specimen through brush platens glued to the specimen surface while compressive stresses are applied along the two remaining axes through fluid cushion systems. In this manner, three totally independent principal stresses can be applied with virtually no tangential surface tractions so that the actual stress state in the specimen is identical to the applied stresses. Stress-strain response curves and strength relations from biaxial tension-compression tests on Indiana limestone and steel-fiber reinforced concrete are presented as examples of the capabilities of the new device.
Axial Pile Loading Test—Part 1: Static Loading
Authors:   ISSMFE Subcommittee on Field and Laboratory Testing
Published: February 2009

The International Society of Soil Mechanics and Foundation Engineering established a technical committee to develop manuals for field and laboratory geotechnical tests. As one of these, recommendations on axial pile loading tests are presented to the profession resulting from four years of worldwide discussion among piling experts of 16 countries. The text is supplemented by notes that indicate details on which no unanimous decision could be obtained.

The document recommends requirements on the test device and the test proceeding. Further, the evaluation of the determination of the test limit load is included because it was felt that much uncertainty would remain if the type of engineering judgment on the test results would be kept out.
The Effect of Clay Content on Liquid Limit from a Fall Cone and the British Cup Device
Authors: Budhu M
Published: February 2009

The many shortcomings of the Casagrande cup device, used almost univerally to determine the liquid limit of soils, led to the investigation of fall cones as alternatives. In two of the four types of fall cones in use, investigators have shown that the differences between fall cone liquid limit values and cup liquid limit values were not large. Evidence is produced to show that the fall cones of the same cone angle would give identical results if the appropriate depth of penetration is specified. Tests conducted using a British/French fall cone and a British cup device reveal that the difference in liquid limit values between these two devices is related to the amount of clay in the soil. A one point fall cone method is shown to be sufficiently accurate to deduce the liquid limit of soils. The fall cone method is a rational alternative to the cup device, and since engineers are interested in strength, the liquid limit could perhaps be defined as the water content at which a soil would have a specific undrained shear strength (say 1kN/m2).
An Underwater Instrument for Determining Bearing Capacity of Shallow Marine Sediments
Authors: Circé RC
Published: February 2009

A small, portable, underwater instrument for measuring carbonate substrate bearing capacity in situ is described. The device was used in various shallow water (< 9 m) carbonate reef environments. Criteria for design and operation were based on ability to deliver controlled levels of stress to bearing plates of various sizes, operability underwater by scuba divers, transportability, and cost.
Determinations and Uses of Strain Distributions in Sand Samples
Authors: Wong RKS , Arthur JRF
Published: February 2009

The determination of strain distributions in dense sand samples is described in this paper. An estimate of all the possible errors during the measurement of strains is also made. It is shown that the much cheaper photographic method can replace radiography under plane strain conditions as a means of recording strains. Detailed strain distributions allow the evaluation of shear apparatus performance, and the strain distributions obtained in the directional shear cell are found to be as uniform as samples tested in the triaxial cell with “frictionless” ends. Using these strain distribution data, the inhomogeneous deformation response to uniform stresses of the most uniform sand samples is revealed and discussed.
Liquid Limit of Soil Mixtures
Authors: Sivapullaiah PV , Sridharan A
Published: February 2009

The liquid limit test is one of the most widely used tests in the soil engineering practice. Several properties, including mechanical properties (for example, compressive index), have correlations with the liquid limit. In this paper detailed investigations of the liquid limit of soil mixturs have been carried out using bentonite, kaolinite, sand (coarse grained, fine grained, rounded and angular shaped), and silts. Based on the results obtained, it has been shown that the liquid limits of soil mixtures are not governed by the linear law of mixtures. While the shape of the sand was not found to influence the liquid limit, the size of the sand particles had a definite influence. Liquid limit obtained by the cone method is lesser than the limit obtained by using the Casagrande apparatus. A good relationship exists between the results of these two methods. A procedure for obtaining the liquid limit of low plastic soil has been suggested.
Pore-Pressure Response of the Piezocone Penetrometer
Authors: Rad NS , Tumay MT
Published: February 2009

Cone penetrometers have been increasingly used in geotechnical investigations during the past several decades. The cone penetration test is recognized as a reliable, simple, fast, and economical in-situ testing technique. Implementation of pore-pressure transducers inside cone penetrometers to monitor the penetration pore pressure during a sounding has strongly increased their applicability and versatility. However, the accuracy of the recorded pore pressures and especially the effect of the degree of saturation of the pore pressure measuring system on the monitored values are debatable. This study is an attempt to provide a deeper insight into this matter.

Theoretical and experimental investigations were conducted. The theoretical work led to the derivation of an equation that may be used to estimate the period of time necessary to achieve an equilibrium inside the pore-pressure measuring system of a partially saturated piezocone. The experimental results revealed that (1) a fully saturated piezocone is capable of responding promptly and accurately to the generated pore pressures during a sounding and (2) the accuracy of the pore-pressure response of a partially saturated piezocone is affected by its degree of saturation as well as the hydraulic conductivity and the geometry of the piezometric element.
Sand Density Measurements for Laboratory Studies
Authors: Trautmann CH , Kulhawy FH , O'Rourke TD
Published: February 2009

A review of laboratory density measurement techniques suggests that the density pan and the density scoop constitute a useful and complementary pair of methods. Both are described in detail and analyzed with respect to bias and random error. Of the two techniques, the density pan is most useful in loose sand and has a coefficient of variation of about 1% for dry, medium-grained sand. The density scoop is most useful in medium to dense sands and also has a coefficient of variation of about 1%. Using these two techniques and a simplified statistical procedure described in this paper, an experimenter can design a program of measurements to measure the density of a given deposit with any desired level of confidence.
Evaluation of Adhesion in Chemically Grouted Geomaterials
Authors: Krizek RJ , Vipulanandan C
Published: February 2009

The mechanical behavior of a grouted geomaterial is influenced by both the cohesive properties of the grout and the bonding between the grout and the solid interface. Not only is the contribution of adhesion to the overall behavior not well understood, but there are no standard test methods to evaluate the adhesive properties at an interface. As one step toward better understanding this adhesive behavior, simple tests were developed to evaluate the adhesive strength under tensile, shear, and mixed mode loading conditions. Quartz rock and a grout mix consisting of sodium silicate, ethyl acetate, formamide, and water were used. Test results show that the bond strength changes with curing time and can be represented by a Mohr-Coulomb failure criterion.
Prediction of the Preconsolidation Pressure and Recompression Index of Soils
Authors: Nagaraj TS , Srinivasa Murthy BR
Published: February 2009

Based on the generalized compressibility equation a procedure is given to estimate the preconsolidation pressure and the recompression index of stress and time dependent overconsolidated soils. This is based on knowledge of (1) the in-situ void ratio, (2) the liquid limit of the soil, (3) the in-situ overburden pressure, and (4) the specific gravity of the soil solids. Estimates of these consolidation parameters, which often are sufficiently accurate, can be obtained without carrying out consolidation tests. The estimated values for specific soils are compared with published data.
Cavity Expansion Tests in a Hollow Cylinder Cell
Authors: Juran I , BenSaid MA
Published: February 2009

This paper presents the use of the hollow cylinder cell in investigating, under laboratory controlled conditions, the response of saturated, consolidated fine grained soils to a cavity expansion. The hollow cylinder cell concept developed originally by Kirkpatrick was adapted to perform cylindrical cavity tests in annular soil specimens with measurement of the excess pore-water pressure generated in the surrounding soil. This modified hollow cylinder cell was also used to study the consolidation of the soil around an expanding cylindrical cavity under a constant cavity pressure and to evaluate available procedures, which can be used to obtain the soil hydraulic conductivity. The equipment, testing procedures, and analysis of both expansion and consolidation test results are discussed.
Triaxial Testing of Brittle Sandstone Using a Multiple Failure State Method
Authors: Cain P , Yuen CMK , Le Bel GR , Crawford AM , Lau DHC
Published: February 2009

The first phase of a recent research program undertaken to investigate sandstone/methane outbursts in coal bearing rocks required the use of a sandstone reference material in the development and trial of the testing procedures to be used. This was because the number of specimens of outburst-prone rocks from the affected mine was limited. Thus another goal of the first phase was to determine a triaxial testing method for characterizing rock properties that minimized the number of specimens required. The International Society for Rock Mechanics (ISRM) multiple failure state method is attractive in this regard because an approximate strength envelope can be determined from a single specimen.

In this test program however the brittle nature of the reference material made control of failure by monitoring axial strain (the ISRM method) impossible; specimens always failed at the first, low or zero confinement, stage. An alternative method of detecting imminent failure in the specimen was developed and applied, yielding results almost identical to those obtained by conventional single state testing.
Differential Flow Patterns Through Compacted Clays
Authors: Peirce JJ , Sallfors G , Ford K
Published: February 2009

The determination of the hydraulic conductivity of compacted clays is vital when the clay is to be used as a liner for contaminant of hazardous waste. Therefore different types of permeameters were used and modified to investigate the homogeneity of a compacted specimens.

Flexible wall and fixed wall permeameters were modified using multiple ring bases to determine the magnitude of differential flow patterns during hydraulic conductivity testing. The hydraulic conductivity was calculated for different portions of the specimen. The outer ring of the specimen was found to have a permeability two to five times larger than that of the core of the specimen, resulting in an overall permeability, which was 50 to 100% higher than that of the core of the specimen. Thorough determination of the variation of the density within a specimen does not explain the variation of the hydraulic conductivity. The clay near the periphery is apparently exposed to a somewhat different type of compaction resulting in a different structure of the clay and thus a higher permeability. Tests with a 19 port base indicated that isolated areas could contain channels where major flow takes place.
Advantages of Midheight Pore Pressure Measurements in Undrained Triaxial Testing
Authors: Fourie AB , Xiaobi D
Published: February 2009

Most soil mechanics laboratories still prefer the use of rough end platens during triaxial testing despite an awareness that nonuniform stress conditions occur within the soil specimen. This practice may to some extent be due to a lack of awareness of the magnitude of inaccuracies which may result. This paper describes results from unconsolidated undrained triaxial compression and extension tests in which pore pressures were monitored at the specimen base and at midheight using a circumferentially mounted miniature transducer. The rate of imposed displacement was varied by two orders of magnitude. The significance of displacement rate and specimen end condition is illustrated by presentation of resulting stress ratios and stress paths. Base measured pore pressures were found to be up to 50% higher than the midheight values, depending on the testing rate used. The results indicated that currently accepted criteria for the determination of acceptable displacement rates are adequate.
Measuring Inherent Load-Extension Properties of Geotextiles for Design of Reinforced Structures
Authors: Wu JTH
Published: February 2009

Existing test methods for measuring the load-extension properties, including the stiffness and the ultimate strength, of geotextiles as they are subjected to confining pressures are reviewed and critically evaluated. In addition, a new test method which surmounts the drawbacks of the existing methods is presented. The new method has three distinct characteristics: (1) it is an “element” test, thus the load-extension properties determined from the test are the inherent properties of the geotextile; (2) the test measures the confined stiffness and strength of geotextiles without inducing soil-geotextile interface adhesion, thereby simulating the predominant operational condition in typical geotextile-reinforced soil structures; and (3) the stiffness and strength obtained from the test are conservative values if soil-geotextile interface slippage does occur in a reinforced structure. The new test method offers a unified and more rational method for determining the load-extension properties of geotextiles in the design and specification of geotextile-reinforced soil structures.
Swelling/Shrinkage Characteristic Curve of Desiccated Expansive Clays
Authors: Hanafy EADE
Published: February 2009

The change in void ratio with change in water content of expansive clayey soils due to soil desiccation and water absorption has been identified as the integral/combined curve referred to as S-curve, which describes both swelling and shrinkage paths in the form of the void ratio versus moisture content relationship.

General characteristics of the S-curve and its determination procedure are described in detail in this paper, including presentation of the theoretical considerations, phase diagrams for both swelling and shrinkage conditions, and the primary paths of the S-curve.

The swelling/shrinkage characteristic curve in the form of the volume change versus moisture content relationship is also presented as a swelling potential chart that can be used to evaluate the swelling potential of desiccated expansive clays.
A New Technique for Measuring the Roughness Profile of Rock Joints
Authors: Lee D-H , Juang CH
Published: February 2009

This technical note describes a new technique for measuring the roughness profile of rock joints or discontinuities. This new technique involves use of a laser displacement meter (LDM) and a linear variable differential transformer (LVDT). The technique improves precision and speed of the measurement. A comparison of this technique with existing methods for measuring the roughness profile is presented.
Soil Column Drainage Modelling Using a Geotechnical Centrifuge
Authors: Cooke AB , Mitchell RJ
Published: February 2009

Equipment has been developed to facilitate supplying a soil column with water or draining a soil column under conditions of constant head while the soil column is under centrifugal forces in a geotechnical centrifuge. Accurate monitoring of the water mass transfer is also facilitated by the equipment. At the completion of a modelling sequence, the soil column may be partitioned for moisture content and chemical analysis with minimal disruption of the moisture content profile. Some preliminary modelling results are included in the paper.
Design Basis for Cells Measuring Shear Stresses in an Interface
Authors: Askegaard V
Published: February 2009

An expression is derived for the measuring error that must be expected when measuring shear stresses in an interface, that is, on foundations, buried pipes, silos, and so forth, by means of a plate-type shear cell fixed along the edge. A prototype cell of this type has been produced and calibration tests carried out using two types of calibration equipment; in the first a uniformly distributed shear load is transmitted to the shear cell while in the second, the shear stress is transmitted through a particulate medium to the wall in which the shear cell is mounted. The accordance between the theoretically predicted measuring error, using the expression derived, and the experimentally determined measuring error is good.
Testing Using a Large-Scale Cyclic Simple Shear Device
Authors: Amer MI , Aggour MS , Kovacs WD
Published: February 2009

Cyclic simple shear testing is considered to be one of the most appropriate ways of reproducing in the laboratory the stresses that would be experienced by an element of soil in level ground subjected to earthquake loading. In the last few years cyclic simple shear testing has been analyzed experimentally and theoretically, and the advantages and limitations of the test presented. The main drawback concerns the lack of complementary shear stresses on the specimen vertical boundary and thereby a selection of the proper specimen size, that is, proper diameter versus height ratio must be carefully considered. The nonuniformity of the strain and stresses in the specimen most likely increases as the specimen diameter versus height ratio decreases. To investigate the specimen size effect on the primary dynamic (cyclic) soil properties, namely, the shear modulus and damping, a large-scale simple shear apparatus was constructed. In it, specimens having diameters from 7.6 to 30.5 cm (3 to 12 in.) and heights from 0.64 to 10.2 cm (¼ to 4 in.) could be tested. Thus a wide range of diameter to height ratios could be obtained. The new testing device, its control system, and the method of preparation and installation of the soil specimens for such a large-scale device are presented and discussed. In addition, a cyclic testing program was conducted on sand and some examples of the data obtained are presented as well.
Significance of Specimen Preparation Upon Soil Plasticity
Authors: Armstrong JC , Petry TM
Published: February 2009

The limits of soil behavior defined by Atterberg and refined by others and the indices resulting from their determination have become vastly important to the design process in geotechnical engineering. The methods utilized to determine these properties are under scrutiny because of the widely varying results that are found. One of the primary sources of this variance was thought to be the modes of specimen preparation.

The research reported on in this paper was conducted to determine the extent of the property variance caused by this part of the testing and to find a specimen preparation that could lead to the most uniform and acceptable result. Thirteen different specimen preparation procedures were studied, and the resulting limits and indices analyzed. The procedure found to be most successful was that affecting the double water layer situation the least. The variance noted was great enough to cause some samples to move from a CH to a CL classification. In all cases the variance noted was significant. The conclusions include recommended procedures and recommendations for further study.