bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Modeling of Drilled Shaft Side Resistance in Sand
Authors: Turner JP , Kulhawy FH
Published: February 2009

Dimensional analysis of deep foundation side resistance is used to formulate the laws of similitude for drilled shaft uplift capacity. The resulting prediction equation for dimensionless side resistance then is tested against the results of static uplift load tests on model drilled shaft foundations in sand constructed at three different scales, all satisfying the same conditions of similitude. The test results and analysis of soil response show that soil dilation, constant thickness of the soil shear zone surrounding the shaft regardless of shaft diameter, and curvature in the Mohr-Coulomb failure envelope at low normal stresses can combine to cause apparent scale effects. These mechanisms are isolated and evaluated quantitatively for the shafts of this study, and apparent scale effects are eliminated by applying correction factors to the load test results. The factors illustrated by this study are used to develop guidelines for: (1) conducting model load tests to avoid scale effects and (2) developing correction factors for small-scale models that may be affected by apparent scale effects.
Geo-Environmental Assessment of a Micaceous Soil for Its Potential Use as an Engineered Clay Barrier
Authors: Mohamed AMO , Yong RN , Tan BK , Farkas A , Curtis LW
Published: February 2009

The ability of the fine fraction of a natural micaceous soil in the Stanleyville area near Perth, Ontario, to retard an acidic waste leachate is examined. Batch and leaching column tests were used to investigate the retention capcity of the natural soil. To investigate the effect of ion competition on adsorption/desorption capacity of the soil, single and multi-components of Pb2+ and Zn2+ were used in batch experiments. The experimental results from column leaching tests were analyzed in terms of adsorption/desorption isotherms, breakthrough curves, and migration profiles of each specific ion in the influent. It was shown that the soil has high adsorption capacity for K+, Pb2+, and Zn2+ as indicated from the concentration profiles of the soil pore fluid with depth during leaching. At the same time, desorption of Na+, Mg2+, and Ca2+ occurred due to ion exchange.

The experimental data were analyzed using a phenomenological approach based on nondimensional analysis, analytical solution via Fourier series, and the root time method. The calculated diffusion parameters are presented and compared with the literature.
Treatment of Oil-Contaminated Soils for Identification and Classification
Authors: Meegoda NJ , Ratnaweera P
Published: February 2009

An experimental investigation was performed to evaluate the effects of oil contamination on soils and to establish a methodology to identify and classify contaminated soils. Identification and classification tests were performed before treatment, cleaning, stabilization, or disposal of contaminated soils.

There are no standards for identification and classification of contaminated soils. Fine-grained, oil-contaminated soils are often identified and classified as granular soils with large particle sizes and may result in selection of improper treatment techniques. In this study, four uncontaminated soils were first identified and classified; then, all four soils were mixed with 3% motor oil. The oil-contaminated soils were first tested for identification and classification and then treated by (1) heating in ovens at various temperatures (low-temperature desorption), (2) adding solvents (solvent extraction), and (3) adding surfactants (treatment with surfactants).

The processed soils were then reidentified and reclassified. Test results showed that treatment with a surfactant produced near-virgin soils for all four soil types. The solvent extraction was adequate only for the silty sand and the silty clay. The low-temperature thermal treatment was inadequate for all four soils. To further confirm the above test results, the low-plastic clay was mixed with 6% motor oil and the above test program repeated. This soil with a higher degree of contamination produced the same results. To provide an explanation for the change in soil behavior due to oil contamination, low-plastic soil was mixed with oil up to 70% by weight and Atterberg limit tests performed. It was concluded that fine-grained soils when contaminated with oil behave as granular soils with particle aggregation. Since soils in this study were artificially contaminated, one should exert caution when applying the results of this study to soils in contact with oil for many years.
Factors Affecting Sand Specimen Preparation by Raining
Authors: Rad NS , Tumay MT
Published: February 2009

Among the available procedures for obtaining reconstituted laboratory sand specimens, pluvial compaction appears to best simulate the natural processes leading to formation of sand deposits. Although widely used for a long period of time, effects of some components of the specimen preparation equipment (sand rainer) on the relative density of the specimen formed have not been comprehensively studied. This paper presents the results of an investigation aimed at studying these effects. The results obtained are used to provide a guide-line for design of a sand rainer.
An Automatic Feedback System for Resonant Column Testing
Authors: Morris DV
Published: February 2009

A test method and electronic circuitry is described that greatly simplifies measurement of resonant frequency in the resonant column test. It utilizes a feedback system to detect resonance automatically without requiring manual adjustment and also eliminates the need for a sine wave audio oscillator or oscilloscope. A constant and controllable strain level in the soil sample is ensured, irrespective of driving frequency or sample condition, by providing a voltage-limiting circuit within the system. The design described will automatically track and display variations in resonant frequency as a result of changes in applied cell pressure and/or strain level, etc.

In addition, double integration allows direct digital output of strain level to be continuously displayed. An alternative (and very rapid) method of measuring damping is also suggested.

Preliminary results are presented for tests performed in this way. An integrated package is shown that replaces the discrete components by a single unit.
Generalized Calibration of a Nuclear Moisture/Density Depth Gauge
Authors: Morris PH , Williams DJ
Published: February 2009

The application of nuclear moisture/density depth gauges to soil deposits has generally relied on calibration by direct correlation with measured values of moisture content and density. In very soft variable deposits such as coal tailings, direct calibration is not possible. A generalized calibration can be developed from first principles based on the elemental composition of the soil being tested and the application of existing theories. Density and moisture content calibrations are considered separately for two different access tubes, and reasonably reliable calibrations are obtained. In applying these calibrations, an iterative procedure is required since the moisture content has a direct bearing on the elemental composition of the moist soil. The paper gives an insight into the operation and important features of a nuclear gauge.
The Preparation of Hollow Cylinder Specimens from Undisturbed Tube Samples of Soft Clay
Authors: Talesnick M , Frydman S
Published: February 2009

The use of torsional-hollow cylinder testing apparatus for research into soil stress-strain behavior has grown over the past decade. Most studies have focused on sands or on cohesive materials reconstituted in the laboratory. Studies involving undisturbed soft clay have been neglected, in part due to the difficulties involved in specimen preparation.

The present paper describes a procedure for the preparation of hollow cylinder specimens of very soft undisturbed clay and their mounting in the triaxial chamber. The procedure involves the use of electrosmosis in order to allow “frictionless” cutting of soft saturated cohesive materials. The specimen is supported laterally, axially, radially, and tangentially throughout the entire procedure.

The procedure could easily be adapted for the preparation of specimens of soft clays for any geotechnical laboratory test.
Measurement of B-Values Less Than Unity for Thinly Interbedded Varved Clay
Authors: Eigenbrod KD , Burak JP
Published: February 2009

During testing of thinly interbedded varved clay from Thunder Bay, Northwest Ontario, in CIŪ-triaxial tests it was found that B-tests carried out following completion of the consolidation stages and prior to shearing never resulted in B-values close to unity. However, B-values close to 1 were obtained when B-tests were performed after failure. It was further detected from additional B-tests that B-values decreased with increasing stress levels. The test results will be presented and discussed with respect to the structure of the varved clay, which is characterized by thinly interbedded soft clay seams and stiff sandy silt seams.
Complex Stress Paths and Validation of Constitutive Models
Authors: Bianchini G , Saada A , Puccini P , Lanier J , Zitouni Z
Published: February 2009

The solution of complicated soil engineering and soil structure interaction problems requires the use of realistic constitutive equations and failure criteria. A recent international workshop held at Case Western Reserve University was aimed at assessing the predictive capability of presently available models for granular noncohesive soils. The results of tests conducted on hollow cylinders at Case and on cubes at the University of Grenoble were used to test the various models. This paper highlights some of the realities of soil testing when the equipment used induces different boundary conditions to the soil samples. It evaluates the predictions submitted to the workshop and examines the adequacy of the various classes of models in predicting simple and complicated stress paths using results obtained from standard tests.
Modified Testing Device to Evaluate MR Properties on Fly Ash Treated Subgrade Soil
Authors: Chang DT-T , Chiang C-E , Chang C-Y
Published: February 2009

The need to obtain reliable resilient modulus (MR) for fly ash treated subgrade soil in pavement thickness design in Taiwan prompted the modification of the existing standard testing device. In the modified device, a load cell and two linear variable differential transformers (LVDTs), conforming to TAI and AASHTO methods, were used to measure the axial load and deformation of specimen. To control the testing and data acquisition process, a computer program for MR of fly ash treated subgrade soil, “MRSS,” was developed using a 14-bit A/D convertor for data processing. The software is capable of simulating various testing conditions, such as load duration, varying repeated loads, and cycle duration. For monitoring purposes, the software is written to plot the stress-time and deformation-time curves, which were found to resemble the shape of a haversine curve. Through the calibration procedure, the performance of this modified testing device was found to be reliable and accurate.
An Automated Electropneumatic Control System for Direct Simple Shear Testing
Authors: DeGroot DJ , Germaine JT , Gedney R
Published: February 2009

This paper describes the design and implementation of an automated electropneumatic control system for direct simple shear testing of cohesive soils. The hardware and software used to perform automated application of consolidation increments and for subsequent constant volume shear of soil specimens is described in detail. Two servo-control algorithms are used to conduct a test, one for application of consolidation increments and another for maintaining constant volume during undrained shear. It is shown that a servocontrol system using a proportional controller can successfully control stress during consolidation increments but cannot control displacement by varying stress as required during undrained shear of cohesive soils. Results are presented which show that while the proportional controller can successfully perform displacement control for mechanical and hydraulic systems it cannot do so for more compliant pneumatic systems. This is primarily due to the fact that pneumatic systems are significantly less rigid due to the high compressibility of air as compared to the compressibility of mechanical systems and hydraulic fluids. While attempting to maintain constant height of the specimen, as is necessary to maintain constant volume during undrained shear, the pneumatic-based system falls into an irrecoverable oscillation of the vertical stress. It is shown that the undrained shear portion of a test required the implementation of the more sophisticated proportional plus integral plus derivative (PID) controller. Unlike the proportional controller, the PID controller easily maintains constant height of the specimen during undrained shear without instability in the vertical stress. Results are given comparing the performance of both the proportional controller and the PID controller during undrained shear of a cohesive soil specimen.
Stress Nonuniformities in Hollow Cylinder Torsional Specimens
Authors: Wijewickreme D , Vaid YP
Published: February 2009

Stress nonuniformities across the wall of hollow cylindrical torsional shear (HCT) specimens under generalized stress conditions are assessed taking into account the nonlinearity in soil behavior. The domain of stress space that results in acceptable levels of nonuniformities is thus delineated for a given specimen geometry. It is shown that previous analyses assuming linear elastic soil grossly overestimate stress nonuniformities in HCT specimens. The HCT device is thus suitable for investigating soil behavior under generalized stresses over a much larger domain of stress space than that thought earlier.
Microscopic Measurement of Sand Fabric from Cyclic Tests Causing Liquefaction
Authors: Ibrahim AA , Kagawa T
Published: February 2009

An experimental study was made to clarify and confirm: (1) the effects of a specimen preparation method on the fabric of sand; and (2) the change of sand fabric due to cyclic loading leading to liquefaction. Microscopic observations were made on the thin sections produced from sand specimens prepared by dry pluviation, dry vibration, and wet tamping methods. This study showed that dry pluviation tends to produce more “random” particle orientations and larger deviation of local void ratios than wet tamping. On the other hand, the dry vibration method produced intermediate results. This difference in fabric has the key impact on the liquefaction resistance of specimens prepared by different methods. Application of cyclic shear tends to alter the initial fabric of sand. For a “randomly” arranged sand mass, cyclic shear tends to line up the orientations of sand particles, resulting in less random arrangement of sand particles. For a “regularly” arranged sand mass, cyclic shear tends to diverge the orientations of sand particles. These findings help explain various static and cyclic behavior of sand.
Prediction of Embankment Settlements by In-Situ Tests
Authors: Bergado DT , Daria PM , Sampaco CL , Alfaro MC
Published: February 2009

The compressibility of soft Bangkok clay preloaded with an instrumented test embankment was studied using the results of a series of in-situ and laboratory tests. In the field, eight screw plate and eight pressuremeter tests were performed at four test levels in the subsoil. In the laboratory, twelve Rowe cell consolidation tests were carried out. The method of Asaoka (1978) was used in determining the coefficient of consolidation from the screw plate test. It was found that Cv values obtained from the Rowe cell consolidation tests were twelve times smaller compared to those derived from the screw plate tests. The soil parameters obtained from the two types of in-situ tests conducted in this study were then used to predict the settlement behavior of the two test embankments, one improved by prefabricated vertical drains (PVD), and the other, on unimproved ground. The difficulty associated with the proper choice of the drained modulus values are highlighted, and it was found that the predicted settlement magnitudes using elastic theory can vary considerably for the ratio of drained and undrained soil moduli, E′/Eu, ranging between 0.25 to 0.50. The undrained modulus from the screw plate test corresponding to the fitted data was found to be 1.38 times the undrained modulus from the pressuremeter test. General agreement with the observed settlement was found using the graphical procedure of Asaoka (1978) and adopting the coefficient of consolidation from the screw plate test.
Development of a Combination Inclinometer-Deflectometer and ADAAS
Authors: Kumbhojkar AS , Israel TD , Arnstan D , Lee SM
Published: February 2009

A newly developed transverse deformation gage, called the combination inclinometer-deflectometer, and special features of its automated data acquisition and analysis system (ADAAS) are described. The hybrid, two-in-one instrument and the ADAAS contribute to the enhancement of accuracy, reliability, and precision of ground movement measurements.
Bromhead Ring Shear Test Procedure
Authors: Stark TD , Vettel JJ
Published: February 2009

Existing test procedures and a proposed modification for the Bromhead ring shear apparatus were found to yield drained residual strengths higher than values back-calculated from field case histories. A new test procedure is presented that yields drained residual strengths that are in excellent agreement with field case histories. The new test procedure utilizes the unmodified Bromhead ring shear apparatus and limits the settlement of the top porous stone, due to consolidation and/or soil extrusion during drained shear, to 0.75 mm. Since the specimen is confined radially by the specimen container, limiting the settlement of the top porous stone minimizes the wall friction that develops along the inner and outer circumferences of the specimen. The reduced wall friction results in the lowest measured residual strength and the best agreement with field case histories.
A New Method for the Determination of Coefficient of Consolidation
Authors: Pandian NS , Sridharan A , Kumar KS
Published: February 2009

The time factor, T, and the degree of consolidation, U, from Terzaghi's theory of consolidation can be shown to have a bilinear behavior when plotted as log (U/T) versus log T. Using this property, a method is proposed for the evaluation of the coefficient of consolidation, Cv. The results obtained using the proposed method are compared with those using other methods in use. A fairly good agreement is obtained, which lends support to the validity of the approach suggested. This approach can be used in all cases including those in which popular methods like square root of time fitting method and logarithm of time fitting method fail.
Measurements of Matric Suction and Volume Changes During Inundation of Collapsible Soil
Authors: Tadepalli R , Rahardjo H , Fredlund DG
Published: February 2009

Reduction in soil volume due to inundation under a constant total stress is a phenomenon referred to as collapse. Collapse is exhibited by soils during a change of state from an unsaturated to a saturated condition. Several researchers have postulated various theories to explain collapse behavior. Recent published research has attempted to explain the collapse phenomenon using theories of unsaturated soil mechanics. However, the theoretical explanations require further verification by experimental data.

A simple experimental procedure is suggested in this paper to measure changes in matric suction and soil volume during inundation. The suggested measurements provide experimental data that can be used to verify the applicability of the unsaturated soil mechanics theories to collapsible soil behavior. Typical test results from this experimental program indicate that collapsible soil behavior can be explained using unsaturated soil mechanics theories.
An Injection-Correction System to Mitigate Membrane Compliance
Authors: Nicholson PG , Anwar HA , Seed RB
Published: February 2009

A computer-controlled injection correction system has been developed to continuously mitigate the adverse effects of membrane compliance for undrained testing of granular soils. The system was developed with the explicit idea that it could be quickly and easily adapted to almost any up-to-date triaxial testing apparatus. Methodology of the system is based on the direct and repeatable relationship between effective confining stress and volumetric compliance. A closed loop computer-controlled system continuously monitors changes in specimen effective confining stresses such that precalculated volumetric compliance errors may be continuously offset by injecting or removing volumes of water equal to those errors throughout the duration of each test. Implementation of the injection-correction system was demonstrated for a uniformly graded medium sand, exemplifying the potential usefulness of such a system.
Computer Automation of Conventional Triaxial Equipment
Authors: Sheahan TC , Germaine JT
Published: February 2009

This paper provides objective guidance on the conversion of existing manual triaxial testing equipment to computer control. An approach called adaptable automation is introduced to facilitate the conversion process. This approach consists of modifying the four basic building blocks of the triaxial system for integration into a computer-automated system and adding components needed for automation which were not part of the manual system. Recommendations are made on necessary changes to the triaxial building blocks, and examples are given from the actual conversion of a largely manual triaxial apparatus. New components required for the automated system are an analog-to-digital conversion device, digital-to-mechanical hardware, and a personal computer with test control software. Performance guidelines for selecting equipment are reviewed as are considerations when developing the software. Methods are described for evaluating the converted system's performance, and typical evaluation results are shown. The paper concludes that, while development of a prototype converted system can be costly and require considerable knowledge of system components, cost savings will be realized as additional prototype-based systems are brought online and system capabilities expanded. More importantly, the converted system allows existing customized testing procedures and hardware to remain in place.
Settlement of Compacted Clay in a Cyclic Direct Simple Shear Device
Authors: Chu H-H , Vucetic M
Published: February 2009

The results of 36 cyclic strain-controlled direct simple shear tests on a low-plasticity compacted clay are presented and analyzed. The tests were conducted in a Marshall Silver-type device, which utilizes the Norwegian Geotechnical Institute (NGI) type of short cylinder specimen confined in a wire-reinforced rubber membrane. Three degrees of compaction achieved by the modified compaction test are encompassed: (1) below the optimum moisture content, (2) at the optimum, and (3) above the optimum. All specimens were sheared under the same vertical consolidation stress. In each test the cyclic shear strain amplitude, γc, was controlled, i.e., the cyclic tests were strain controlled. The range of γc was between 0.008 and 4.6%. The test results show a very consistent behavior of the clay at all three moisture contents. At small cyclic shear strains below γc ≅ 0.1%, the stress-strain behavior is slightly nonlinear, i.e., close to linearly elastic, and the vertical settlement is negligible. In some tests such nondestructive behavior was recorded up to γc ≅ 0.2%, showing that for the clay tested, the volumetric threshold shear strain, γtv, ranges between 0.1 and 0.2%. At γc larger than γtv the cyclic stress-strain behavior becomes nonlinear and a continuous settlement with the number of cycles, N, occurs. The results do not show a clear relation between the rate of settlement with N and the degree of the compaction and moisture content. For different moisture contents, similar settlements were obtained for given γc and N. The study also shows how to arrange the specimen setup and measuring system to eliminate the effect of the simple shear apparatus compliance. In such an arrangement very small shear strains can be applied and successfully measured.
A Thickness Equation for Nonwoven, Needle-Punched Geotextiles under Normal Loading
Authors: Weggel JR , Gontar WA
Published: February 2009

An equation to predict the thickness of nonwoven, needle-punched geotextiles under normal compressive loading is proposed. The equation is t=(t0−t∞)e−ασ+t∞ in which, t0 is the initial thickness, t∞ is a limiting thickness, σ is the normal stress, and α is an empirical coefficient. Comparison with thickness data obtained in multiple tests on eight different geotextiles using an in-plane, radial flow device results in excellent agreement for normal stresses up to about 372 kPa. Mean square errors are typically less than 0.017 mm. An equation for the limiting thickness, t∞, is developed based on the observation that under compressive loads at the limiting thickness, nonwoven, needle-punched geotextiles have their porosity reduced to about 91% of the initial value.
Monotonic and Cyclic Loading Behavior of Two Sands at Small Strains
Authors: Lo Presti DCF , Pallara O , Lancellotta R , Armandi M , Maniscalco R
Published: February 2009

The shear modulus of freshly deposited specimens of two different sands was measured in a resonant column (RC)-torsional shear (TOS) apparatus. The soil specimens studied included a calcareous, crushable, well-graded, coarse-to-medium sand containing about 2% fines (Quiou sand) and a silica, uniform, coarse-to-medium sand without fines (Ticino sand).

A brief description of the apparatus, with particular attention to the facilities used for the monotonic loading condition, is given together with a concise literature review.

The shear moduli of the two sands in cyclic dynamic tests (RC) were compared with those measured in static monotonic loading torsional shear tests. It is shown that at small strains of less than about 0.001%, the shear moduli of the Ticino sand obtained from the dynamic tests and the static monotonic loading tests are the same, which means that the behavior of the sand at these very small strain levels is strain-rate independent and recoverable, namely elastic. In the case of Quiou sand, the shear moduli at small strains obtained from the dynamic tests are 20% greater than those from the static monotonic loading tests. The authors believe this difference is due to the sand crushability. It is also shown that the strain level dependency of shear modulus at larger strain levels is smaller under cyclic loading conditions than in monotonic loading conditions. The effects of precompression and cyclic prestraining are also examined.
The Continuous Abrasion Index for the Assessment of Rock Abrasion
Authors: Al-Ameen SI , Waller MD
Published: February 2009

The continuous abrasion test is a new and simple test for evaluating the abrasive potential of rock material where attrition or low-stress sliding wear problems exist. The test is sensitive to the abrasive mineral content in the host rock and was found to be very suitable in comparing the degree of abrasiveness of various sedimentary rocks and in particular coal measures rocks. The wear area generated on a tested ball bearing is used as the Continuous Abrasive Index value for the tested rock. Several types of abrasive wear pattern were recognized on the tested steel ball; these can be used as a guide for the assessment of the abrasive potential of the rock. The exploitation of this new test has led to a new rock classification index according to the abrasive potential of the rock.
Numerical Modeling of a Thermal Conductivity Matric Suction Sensor
Authors: Xing A , Fredlund DG
Published: February 2009

Thermal conductivity matric suction sensors appear to be a promising device for the measurement of suction in soil. The technique indirectly measures matric suction by measuring the thermal conductivity of a ceramic block. This paper uses both a spherical and a cylindrical porous medium to simulate the heat flow in a thermal conductivity matric suction sensor. It is found that, although the transient temperature at the center of the sensor is heavily dependent on the material of the thermocouple and the heating device, the steadystate temperature is primarily determined by the thermal conductivity of the ceramic block. Therefore, accurate measurements can be obtained by using a longer heating period or by selecting a lower-heat-capacity material for the thermocouple and the heating device. Optimal sizes of the sensor for given heating rates and heating periods are calculated using a finite difference method. A multilayered sphere was also used to simulate the situation where the size of the sensor is not sufficiently large and an error occurs due to the influence of the surrounding soil. The numerical model is verified by comparison with the theoretical solution of a special case.
Development of a Transparent Material to Model the Geotechnical Properties of Soils
Authors: Iskander MG , Lai J , Oswald CJ , Mannheimer RJ
Published: February 2009

Measurement of three-dimensional deformation patterns and flow characteristics within a soil continuum are usually limited by the fact that soil sensors do not provide a continuous image of the measured continuum. Additionally, soil sensors exhibit static and dynamic characteristics that are different from those of the surrounding soils and therefore can change the response of the measured continuum. Tests conducted with a transparent material which has properties that closely model the geotechnical properties of natural soils can potentially circumvent these experimental problems if the response of a model transparent continuum can be measured using nonintrusive optical visualization techniques.

This paper demonstrates the feasibility of producing transparent materials which exhibit macroscopic properties representative of the geotechnical properties of natural soils. The transparent “soils” discussed in this paper were made by consolidating suspensions of amorphous silica in liquids with matching optical refractive indices. The measured shear strengths and permeabilities of the transparent soils are characteristic of natural clays and silts. The stress-strain response of transparent soils is characterized by large strains during consolidation and shear.
Effect of Preparation Technique on Permeability and Strength of Cement-Grouted Sand
Authors: Schwarz LG , Krizek RJ
Published: February 2009

The effectiveness of cement grouting is generally evaluated in terms of the improvement attained in the engineering properties of the grouted soil. Although this degree of improvement should logically be related to the amount of cementitious particles present in the pore spaces of the grouted sand, and indeed is to some extent, the method of preparing the specimens can exert an even stronger influence. Two significantly different preparation procedures—injection and hand mixing—were used to combine sand with a microfine cement grout at three different water-to-cement ratios. In the hand-mixing technique, a measured volume of grout (relative to the total void volume of the sand) was mixed mechanically with the sand, whereas in the injection method the grout permeated the sand through interconnected pore channels. Immediately after preparing the injected specimens, they were disassembled and an elutriation and filtration procedure was used to quantify the mass of cement particles deposited in the voids of the sand. For grouts with corresponding water-to-cement ratios, the injected specimens manifested higher cement contents than their hand-mixed counterparts with voids completely filled with grout. However, permeability and strength tests on companion specimens cured for 7 or 48 days indicated that injected specimens were generally somewhat stronger, but considerably more permeable, than hand-mixed specimens; this is attributed to the vastly differing mechanisms that govern the distribution and packing arrangement of the cement particles within the void spaces and on the sand grains.
Effect of Short Duration of Load increment on the Compressibility of Soils
Authors: Sridharan A , Sivapullaiah PV , Stalin VK
Published: February 2009

This study concerns the effect of duration of load increment (up to 24 h) on the consolidation properties of expansive black cotton soil (liquid limit = 81%) and nonexpansive kaolinite (liquid limit = 49%). It indicates that the amount and rate of compression are not noticeably affected by the duration of loading for a standard sample of 25 mm in height and 76.2 mm in diameter with double drainage. Hence, the compression index and coefficient of consolidation can be obtained with reasonable accuracy even if the duration of each load increment is as short as 4 h.

The secondary compression coefficient (Cαε) for kaolinite can be obtained for any pressure range with 1/2 h of loading, which, however, requires 4 h for black cotton soil. This is because primary consolidation is completed early in the case of kaolinite. The paper proves that the conventional consolidation test can be carried out with much shorter duration of loading (less than 4 h) than the standard specification of 24 h or more even for remolded fine-grained soils.
Soil-Geogrid Reinforcement Interaction by Pullout and Direct Shear Tests
Authors: Alfaro MC , Miura N , Bergado DT
Published: February 2009

Pullout and direct shear tests have been conducted to investigate the soil-reinforcement interaction behavior in pullout and direct shear mechanisms. An apparatus—discussed in this paper—has been developed that is capable of performing both pullout and direct shear tests. Displacement measurements to monitor dilatancy on the backfill soil during pullout tests are incorporated in the apparatus. Test results for the geogrid type of reinforcement embedded in dense granular soil are discussed. The devised testing program provides valuable information on the appropriate interaction models and parameters that will be employed in the design and analysis of reinforced soil structures. The dilatancy measured in the laboratory may also provide useful information on the increase of interface shear resistance when dilatancy is restrained under field conditions.
External Measurement of Axial Strain in the Triaxial Test
Authors: Bressani LA
Published: February 2009

The errors involved in measuring axial strains in the triaxial test are reviewed based on previously published results. A technique is described to allow more reliable external measurements to be obtained and used for strain calculations. The technique is simple, inexpensive, and can be implemented in any soils laboratory. Comparisons are made between the strains obtained by this method and those using local transducers (connected to the specimen); satisfactory results are obtained. Triaxial tests were made on specimens of an artificially bonded soil, Corinth marl, and remolded London clay. Errors involved in previous tests are explained, and the “bedding error” is defined in a more precise way. In some tests, this error was eliminated due to a combination of factors such as soil grading, the finishing quality of the specimen surfaces, and the ratio of confining pressure to soil strength.
Geosynthetic/Soil Interface Friction Angles Using a Rotation Shear Device
Authors: Evans MD , Fennick TJ
Published: February 2009

A modified rotation shear device was used for measuring interface friction angles between soils and geosynthetics. The device was modified so that a geosynthetic specimen can be attached to the upper platen. A reliable method for cutting and attaching geosynthetic specimens to the device is described. The geosynthetic mounting system is simple, strong, and easy to remove. Interface friction angles and interface efficiencies for two ash samples and Boston Blue Clay with three geosynthetics are reported and compared. A range of strength increase is reported for a given soil with change from a smooth geomembrane to a textured geomembrane or nonwoven geotextile. Shear displacements up to 300 mm are quantified in the paper, showing that large, unidirectional displacements may accumulate in the rotation shear device.
Effect of Rib Spacing on Deformation of Profile-Wall Plastic Pipes Buried in Coarse Granular Backfill
Authors: Sargand S , Masada T , Hurd JO
Published: February 2009

Several different types of plastic pipe products were instrumented, buried in coarse granular backfill, and subjected to monotonic, distributed load in the field. During each field test, data were recorded from strain gages, linear variable differential transformers, and earth pressure cells by computerized data acquisition units.

Review of the deflection data from 14 tests revealed a pattern on the initial deflection that can be explained by considering a dimensional ratio between the rib spacing, S, and maximum particle size, dmax. Earth pressure cell readings taken in the springline region appeared to support this. Based on this observation, a recommendation was made that the S/dmax ratio should be either less than 0.6 or larger than 2.6 to prevent excessive initial deflection under relatively low levels of loading.
A Flexible Strain Gage for Soil Testing
Authors: Li XS
Published: February 2009

A novel strain gage for the measurement of soil deformation is introduced. The gage is based on the principle that the change in the length of a coil is linearly related to the change in its inductance. The gage measures a wide range of strains and can be easily installed on a soil specimen in any direction; therefore, it is particularly suitable for the measurement of deformations of in situ subsurface soil. This paper reports the principle and the characteristics of the gage. A discussion on further improvements is also given.
Determination of Coefficient of Consolidation from Early Stage of LogtPlot
Authors: Robinson RG , Allam MM
Published: February 2009

The standard curve-fitting methods, Casagrande's log t method and Taylor's root t method, for the determination of the coefficient of consolidation use the later part of the consolidation curve and are influenced by secondary compression effects. Literature shows that secondary compression is concurrent with primary consolidation and that its effect is to decrease the value of the coefficient of consolidation. If the early part of the time-compression data is used, the values obtained will be less influenced by secondary compression effects. A method that uses the early part of the log t plot is proposed in this technical note. As the influence of secondary compression is reduced, the value obtained by this method is greater than that yielded by both the standard methods. The permeability values computed from Cv (obtained from the proposed method) are more in agreement with the measured values than the standard methods showing that the effects of secondary compression are minimized. Time-compression data for a shorter duration is sufficient for the determination of Cv if the coefficient of secondary compression is not required.
Determining a Pavement Modulus from Portable FWD Testing
Authors: Livneh M , Livneh NA , Elhadad E
Published: February 2009

This paper assumes that there is room for an additional measuring device that, on the one hand, will serve mainly as an in situ device not requiring complicated back-calculation procedures and, on the other hand, will not involve large volumes of in situ materials as presently required by the falling weight deflectometer (FWD). Such a device is the new portable FWD (PFWD). Comparative tests with this device show no significant correlation between the central deflection measurements taken on the asphalt surface and the corresponding Benkelman-beam-measured deflections. This is due to the fact that the PFWD device “senses” only the upper layers of the pavement, down to no more than a small thickness, whereas the two other devices “sense” all pavement layers down to the subgrade medium, as well. A composite-pavement modulus of elasticity (Ep) can still be derived from the PFWD measurements, but only with the performance of additional measurements on the asphalt surface, followed by coring of the asphalt layers down to their far bottom. In this way, the above Ep value is calculated for the full structural thickness and for the standard radius of the contact area obtained from the PFWD testing, i.e., the modulus of elasticity (EA) of the asphalt layers and the modulus of elasticity (EG) of the granular layers. A comparison of the above Ep values calculated from the PFWD outputs, with the values derived from the conventional FWD measurements, led to the introduction of a correction factor that varies with the ratio of the thickness of the asphalt layers to their elastic modulus. The lower the ratio, the closer the correction factor approaches the value of 1.0.
Upgrading Equipment and Procedures for Stress Path Triaxial Testing of Coarse-Grained Materials
Authors: Flora A , Modoni G
Published: February 2009

Advanced laboratory testing is often the only way to gain an insight into the mechanical behavior of soils in the whole range from small strains to failure, which in some cases is required for the engineering modeling of complex structures. When such structures are rockfill dams, the use of a large apparatus in-laboratory is virtually unavoidable because of particle size, even though testing becomes far more difficult than usual. This paper presents problems arising from the upgrading of an existing large triaxial cell in order to provide fully automated stress-path control. Because of the large dimensions of the apparatus, implementation of both stress rate and strain rate controls posed a number of unusual problems. Even though the control had to be carefully tuned in order to consider strain-softening behavior, the adopted procedure proved successful. The new cell produced good results for different kinds of stress paths, with satisfactory control in all stages.
Grain-Size Analysis by Buoyancy Method
Authors: Bardet J-P , Young J
Published: February 2009

A new routine experiment referred to as buoyancy analysis is proposed to determine the grain-size distribution of fine-grained soils. The buoyancy analysis is based on the sedimentation principles of the hydrometer and pipette analyses. It determines the percent by weight finer than a given grain size by measuring the buoyant weight of a 2.5-cm-diameter sphere immersed in the soil suspension. The buoyancy analysis is slightly more accurate than the hydrometer analysis, has a shorter duration, and its readings can be fed directly into a computer. It yields results identical to those of the hydrometer analysis when the sphere is immersed within the depth range of the hydrometer bulb.
Microcomputer Based Data Acquisition Systems for Centrifuge Modeling
Authors: Shen C-K , Li X-S , Kim Y-S
Published: February 2009

A general discussion is given as to how microcomputer based data acquisition systems can be used in centrifuge model testing. Special attention is paid to the transmission of signals from the rotating section to the stationary section of the system. Both the direct and indirect methods of signal transmission are illustrated. Examples of applications are cited. It is concluded that the adoption of a computerized system can greatly enhance the accuracy and speed of the data acquisition process for centrifuge model studies of geotechnical structures.
Measurement of Volumetric and Linear Shrinkage on Black Cotton Soil
Authors: Subba Rao KS , Satyadas GC
Published: February 2009

Experimental investigations on the shrinkage of expansive black cotton soil have been made to study the process of shrinkage. Tests have been conducted on compacted soil specimens with different water contents under controlled conditions of temperature and humidity. The changes that take place in the air and water phases of specimens have been analyzed, and shrinkage paths have been examined both for volumetric and linear shrinkage. Volumetric shrinkage is shown to take a unique shrinkage path in terms of water loss, independent of water content or rate of shrinking. In contrast, the linear shrinkage paths are shown to be dependent on conditions under which shrinkage takes place.
Effect of Grain Characteristics on Liquefaction Potential—In Search of Standard Sand for Cyclic Strength
Authors: Ishibashi I
Published: February 2009

Since the original Monterey 0 sand, which had been used for cyclic triaxial testing system calibration, is not available any more, the search for an alternative sand was started. In order to provide useful information for the above purpose, liquefaction potentials were evaluated for Monterey 0 and 0/30 sands and for ASTM Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube) (C 109) Ottawa sands from various sources. The results clearly indicated that the liquefaction potential was very sensitive to slight changes in material properties (mean grain size, coefficient of uniformity, sphericity, and volume decrease potential).
Geotextile Filters for a Large Liquefaction Tank
Authors: Hryciw RD , Cornet J-M , Dowding CH
Published: February 2009

A large liquefaction tank used to prepare sand for laboratory testing required a 107-cm (42-in.) diameter filter. The filter was needed to separate the sand from water diffusers below, to facilitate a uniform upward flow of water, and to filter out undersired fines. The chosen design consisted of two geotextile fabrics sandwiched between a perforated plexiglass sheet and a steel grating. Selection of the geotextiles was based on the fabrics' porosities, permeabilities, and pore sizes. The system has been a success and has required no maintenance in over four years of usage.
Use of Time Series in Geotechnical Data Analysis
Authors: Wu TH , El-Jandali A
Published: February 2009

Methods of time series analysis based on the Box-Jenkins method were used to analyze random variations and inherent variability in geotechnical test data. The paper presents a summary of the time series models and their application to the analysis of data from unconfined compression tests, field vane tests, and cone penetration tests. The integrated-moving-average-autoregressive model was found to be a versatile tool and served this purpose well. The model permits the determination of the autocavariance function and the random testing error that best fit the test data.
Electro-Servo Control System for Thermomechanical Properties Testing
Authors: Myer LR
Published: February 2009

The main features of a system for pseudo-static thermomechanical triaxial rock testing systems are discussed. The system emphasizes ease of control and versatility in performing complex load/deformation paths required in many testing applications in the temperature-pressure range of 20 to 200°C and atmospheric pressure to 70 MPa. The pressurization system, utilizing electric motor-driven pumps and a computer-aided data acquisition/motor control system is described in detail. Example results are given of the application of the test system in determination of thermoelastic properties of a quartz monzonite rock.
A New Automatic Volume Change Monitoring Device
Authors: Rad NS , Clough GW
Published: February 2009

Automated testing systems are presently widely used in soil laboratory strength testings to monitor load, displacement, and pressure. A new device is introduced here for automatic measurements of the volume change of soil specimens during drained triaxial tests. The device is versatile and capable of monitoring volumetric changes of soil specimens with various dimensions, volume change characteristics, and degrees of saturation. It can also be used to measure the pore pressure inside a soil specimen during an undrained test.