bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory Measurement of Small Strain Shear Modulus Under K Conditions
Authors: Thomann TG , Hryciw RD
Published: February 2009

A new device to measure the small strain shear modulus (Gmax) under a no lateral strain condition has been developed. The techniques for measuring Gmax are discussed, with emphasis on bender element techniques. The performance of the bender elements are compared with results from simultaneous resonant column tests. An in-depth description of the lateral stress measurement system, the Gmax determination technique, and the measurement of vertical strain is presented along with representative test results to demonstrate the performance of the device.
Automated Measurement of Slurry Surface Settlement
Authors: Tan S-A , Tan T-S , Liang KM
Published: February 2009

An automated float method for measuring slurry surface settlement is described. The system consists of a Perspex float which is denser than water but lighter than the slurry into which it penetrates slightly and floats on the slurry/water interface. Settlement of this float is then automatically tracked using an LVDT. Comparison with direct cathetometer measurement demonstrates that except for the initial penetration the float's depth of embedment into the slurry surface is unchanged as settlement progresses. Hence it is able to follow the settlement of the slurry surface. This method is then used to measure quickly and accurately the surface settlement of kaolin during self-weight consolidation tests under single drainage condition. The initial rate of settlement is then used to determine the permeability of the slurry, which is not an easy property to measure using other methods.
Using an Automated Rowe Cell for Constant Rate of Strain Consolidation Testing
Authors: Sheahan TC , Watters PJ
Published: February 2009

The paper describes the automation and calibration of a hydraulic Rowe consolidation cell that tests 151-mm-diameter by 60-mm-high specimens. The associated measurement instrumentation for the cell and specimen preparation procedures are also described. The cell was used to perform a set of one-dimensional constant rate of strain (CRS) tests at two vertical strain rates, 0.1 and 1%/h. The nonlinear CRS theory of Wissa et al. (1971) is presented, including methods for interpreting test results at higher strain rates. The results from the Rowe cell tests conducted on resedimented Boston Blue Clay are compared to those from more conventional incremental loading (IL) oedometer tests (63.5-mm-diameter by 23-mm-high specimens). For both the 0.1%/h tests (in which negligible excess pore pressure was generated at the undrained specimen base) and the 1%/h tests, the compression curves compare well with the baseline IL oedometer test curves. Values of preconsolidation pressure, σ′p, averaged 94.0 kPa in the Rowe tests and 94.5 kPa in the IL oedometer tests. The compression ratios, CR = Δεv/Δ log σ′v, in the virgin compression range were slightly lower in the Rowe cell tests (average 0.156 versus an average CR = 0.173 in the IL oedometer tests), which may be due to different testing conditions (e.g., back pressure in the Rowe cell) or the larger Rowe cell specimen. The coefficient of consolidation and hydraulic conductivity values computed from the Rowe cell tests are essentially identical with regard to stress level to the IL oedometer tests. The automated Rowe cell data indicate that the device offers a reliable and potentially rapid method for determining consolidation parameters, including hydraulic conductivity.
Measurements of Soluble Salt Content of Soils from Arid and Semi-Arid Regions
Authors: Karakouzian M , Pitchford A , Leonard M , Johnson B
Published: February 2009

Soils with soluble salts occur in arid regions worldwide. Depending on the amount of soluble salts present, treatment of these soils may be needed before construction. In engineering, the amount present is usually determined gravimetrically by finding the weight loss for a soil diluted with a fixed quantity of water. However, if the soluble salt content is evaluated with an insufficient amount of water, some of the salt present may not dissolve. This condition, termed “salt saturation,” may cause the amount of soluble salts present to be underestimated. To identify the correct dilution, this paper proposes checking successive dilutions until an unsaturated solution is obtained. This can be accomplished using either gravimetric or electrical conductivity measurements to detect salt saturation. The volume of water used to determine percent soluble salts can then be adjusted accordingly. This paper describes how to find the most suitable dilution using either method and how to determine the percent of soluble salts. Using this approach, five different soils from Las Vegas, Nevada, were evaluated. Unsaturated water-soil dilution ratios ranged from 2:1 to 100:1. In two cases, the 2:1 dilution was adequate, but for the other three it was not. Soil “M” exemplified this best: percent soluble salts increased from 1% measured at a 5:1 dilution (indicating a leave-in-place/no-action recommendation) to 7% at a 100:1 dilution (indicating a removal recommendation). This result illustrates the importance of using an unsaturated dilution for determining percent soluble soil.
Measuring Anisotropic Elastic Properties of Sand Using a Large Triaxial Specimen
Authors: Hoque E , Tatsuoka F , Sato T
Published: February 2009

An advanced automated triaxial testing system developed to characterize elastic behavior of soils is described. Small axial and lateral strains of a large rectangular prismatic specimen were measured locally at various stress states along a specified stress path, which was achieved by automatically controlling axial load and confining pressure. Elastic deformation was measured by applying very small cycles of axial or lateral stress at each given neutral stress state. Typical test data for air-dried sand are presented. It is observed that the elastic Young's modulus is a rather unique function of the normal stress in the direction of the major principal strain increment, and therefore elastic deformation characteristics of sand become anisotropic under anisotropic stress conditions.
A Flow Pump System for Assessing Clay Barrier-Permeant Compatibility
Authors: Kashir M , Yanful EK
Published: February 2009

This paper presents the performance, reliability, and features of a hydraulic conductivity, k, testing equipment specially designed and fabricated for clay barrier-permeant compatibility studies. The key component of the equipment is a flow or infusion/withdrawal pump that is used to deliver a constant and continuous flow of permeant at some prescribed rate through two stainless steel syringes to a soil specimen. The pump has a switch that allows the motor direction to be changed to allow one syringe to empty while the other is filling. This provides an uninterrupted flow of permeant to the specimen, unlike most traditional testing equipment that requires complete stoppage of permeation in order to provide a fresh supply of permeant. In some cases, re-establishment of flow pressures can take a long time and therefore affect the attainment of chemical equilibrium and specimen volume changes during compatibility testing. A Plexiglas cell containing an inflatable rubber diaphragm is used in the present equipment as a permeant supply tank to prevent the exposure of the permeant to air, therefore making the equipment particularly suited for testing with volatile organic liquids and redox-sensitive permeants such as acid mine drainage. Furthermore, this cell is connected to a back pressure supply to decrease the time required for the pressure to return to its original value after switching gears. The advantage of the equipment includes a graphic-based data acquisition system that allows test parameters such as hydraulic gradient, hydraulic conductivity, volume change, and room temperature to be continuously monitored and displayed on a computer monitor screen. The performance and features of the equipment are demonstrated with a series of k-tests on clayey soil specimens permeated with water and then with acid mine drainage (AMD). The data indicated that, while AMD did not change k, it may have dissolved some primary soil minerals such as calcite and dolomite, which in turn buffered the pH of the effluent from a specimen permeated with more than ten pore volumes of AMD.
Friction Angle Between Expanded Shale Aggregate and Construction Materials
Authors: Valsangkar AJ , Holm TA
Published: February 2009

Results of an experimental program are presented for the interface friction mobilized between expanded shale lightweight aggregate and commonly used structural materials: formed concrete, steel, and wood. A large-size direct shear device is used to perform tests. The mobilized friction between lightweight aggregate and solid surfaces of construction materials are compared with interface angles of friction associated with coarse normal-weight aggregates. The results provide useful design information on the appropriate mobilized angle of friction to be used while designing retaining structures with lightweight aggregate as backfill. The data are also useful in estimation of skin friction for piles driven through lightweight aggregate fills.
Evaluation of True Cν and Instantaneous Cν, and Isolation of Secondary Consolidation
Authors: Tewatia SK
Published: February 2009

It is shown that the presence of a distinct straight line in the initial portion of settlement versus the square root of time plot indicates that soil follows theoretical behavior and that there is no initial and secondary compression in the straight line portion. If the coefficient of consolidation, cν, is determined using the data of only this portion, it can be regarded as the true cν. Secondary consolidation essentially starts after 60% consolidation and runs superposed over the primary consolidation. Its effect is to gradually decrease cν so that at every instant of time it is a new Terzaghian soil with a new cν and other consolidation parameters. Characteristics of linear and semi-log plots of U versus U, where U is the degree of consolidation and U is the theoretical velocity, are used for determining true cν and instantaneous cν, and for isolation of secondary consolidation from the experimental consolidation curve.
A Simplified Method for Assessment of Volume Change Behavior of Rockfill Material
Authors: Thallak SG , Nagaraj TS , Yaligar P
Published: February 2009

In this paper an attempt was made to generalize the results of laboratory tests on modeled rockfill materials so as to evolve a simplified method for assessment of their bulk mechanical properties from minimum test data with an acceptable degree of confidence. Examination of the experimental data of the modeled rockfill materials from different sites revealed that the plots of logarithm of strain at failure against logarithm of confining pressure are linear. A trend of increase in failure strain with increase in confining pressure and maximum size of particle is also observed. The simplified approach high-lights prediction of volume change properties of rockfill materials during isotropic consolidation and triaxial state of stress over a range of confining pressures and particle sizes. This approach is based on the results of only two tests carried out at two different confining pressures for a selected maximum particle size on modeled rockfill material with the use of the parallel gradation technique. The two-test approach and its application in engineering design of rockfill materials is illustrated by means of selected experimental data available in the literature.
Plummet Balance—A Potential Tool for Subsieve Particle Size Analysis
Authors: Nagaraj TS , Sivapullaiah PV
Published: February 2009

Particle size distribution analysis as an inferential soil parameter plays a dominant role in geotechnical engineering. This investigation encompasses laboratory study of subsieve particle size analysis by hydrometer, pipet, and plummet balance methods to assess their relative performances and also to examine the critical factors that influence the results obtained by the plummet method. The results of this investigation indicate that for a plummet immersion of 20 cm the particle size distribution would be similar to that obtained by hydrometer and pipet methods. The marginal differences would in no way affect either the classification of the soil or the inferred properties of soils.
Statistical Estimation of Compression Index
Authors: Koppula SD
Published: February 2009

The amount of compression a soil will experience depends, among other factors, on its compression index Cc which may be determined through consolidation tests on undisturbed or remolded soil samples. Alternatively empirical relationships between Cc and other physical properties such as liquid limit or void ratio may be used.

It has been postulated that empirical relationships between Cc and other readily determined soil properties are of much practical importance especially during planning stages, because these relationships permit computations of approximate settlements of structures founded on cohesive soils without the benefit of conducting consolidation tests. These empirical relationships form the basis on which rational decisions can be made as to the suitability of a foundation site.

The data from more than 130 consolidation tests performed on cohesive soils are statistically examined. Ordinary least squares and ridge regression techniques are used to obtain linear models for the variable Cc and the results are compared with published results. It is concluded that a simple linear relationship between the compression index and the initial water content yields highly significant results.
Incremental Loading Device for Stress Path and Strength Testing of Soils
Authors: Nagaraj TS , Murthy MK , Sridharan A
Published: February 2009

A new incremental loading device has been designed and fabricated to hydraulically control the axial stresses in triaxial compression and extension. Several different types of stress paths may be used during shear testing without the problems associated with conventional stress-controlled tests using dead weights. The versatility of the loading device is demonstrated by presenting the results of typical tests. Other potential uses of this test apparatus are also cited.
A Mechanistic Model for Strength and Fatigue of Cement-Treated Soils
Authors: Raad L
Published: February 2009

A mechanistic model for strength and fatigue of cement-treated soils is developed using the Griffith failure theory for the purpose of understanding the structural behavior of cement-treated bases in pavements. Failure under static loads is assumed to occur when the tensile stress at the tip of the most critically oriented flaw reaches a value characteristic of the material. This static failure model is used to study fatigue behavior under repeated stresses. Results of repeatedload triaxial tests on a clayey gravel soil cement are used to define fatigue failure criteria for cement-treated soils. The analytical fatigue model developed is used to derive a cumulative damage hypothesis. According to this hypothesis, fatigue behavior under compound loading depends on the sequence and magnitude of applied loads and the curing age of the cement-treated material. The hypothesis also suggests that Miner's rule could lead to unconservative predictions of fatigue life under random loading conditions.
A Ring Torsion Apparatus for Evaluating Friction Between Soil and Metal Surfaces
Authors: Yoshimi Y , Kishida T
Published: February 2009

A ring torsion apparatus was used to evaluate friction between-dry sand and a steel surface over wide ranges of surface roughness and sand density. The deformation of sand near the steel surface was observed by X-radiography. The apparatus is suitable for evaluating skin friction under well-defined test conditions. The test results show that frictional resistance is primarily governed by the roughness of the steel surface, irrespective of the density of the sand.
An Electropneumatic Cyclic Loading System
Authors: Chan CK
Published: February 2009

This paper reviews some of the current systems in use for the application of cyclic loads to soil specimens. Their main features and principles of operation are described. A relatively low-cost electropneumatic system recently developed at the University of California at Berkeley is described in detail. This system provides sinusoidal and other shape load traces using normal compressed air controlled electronically and is an assembly of commercially available components.
New Sampler for Drilling in Noncohesive Soils
Authors: Johansson HG , Söderström T
Published: February 2009

Taking representative and sufficient samples of noncohesive soils, for example, gravel, sand, and different types of till from boreholes has always been a problem. In Sweden some samplers with very heavy supplementary equipment were used during the 1950s and 1960s. During the last three years a sampler for noncohesive soils has been developed in Sweden. The sampler has been tested in different soils over the whole country.

The sampler provides samples especially for physical and chemical property tests. The sampled soils, especially the tills, have shown very small disturbances. It has been easy to locate and determine different strata. The visual determination in the field of the grain size distribution has correlated well with laboratory analysis. The large quantities of the samples have resulted in a reliable determination of the soil characteristics. Boulders and stones have been drilled through. Samples of soils below the groundwater level as well as samples of underlying bedrock have been obtained.
Temperature Controlled Microwave Drying of Soils
Authors: Charlie WA , Von Gunten MW , Doehring DO
Published: February 2009

The use of temperature controlled microwave drying for the rapid determination of the moisture content of clay soils was investigated. Six soils having plasticity indexes ranging from five to fifty were tested. Temperature controlled microwave drying correlated greatly with water contents obtained from conventional temperature controlled drying. Drying at full microwave power without temperature control indicated higher water contents than drying by conventional means. Compared to the conventional oven method, drying times were approximately 13 times faster when full power microwave techniques were used and two to seven times faster when temperature controlled microwave operations were used.
Suggested Practice for Pressuremeter Testing in Soils
Authors: Winter E
Published: February 2009

A standard practice is suggested for pressuremeter testing in soils that is based on the procedures developed by Menard and adopted by many organizations and firms in the United States. The practice describes the apparatus, calibration, testing procedure, calculations, and presentation of data.
Sensitivity Study of a Ground Probing Radar System
Authors: Bowders JJ , Lord AE , Koerner RM
Published: February 2009

A study was undertaken to determine the sensitivity of a ground probing radar (GPR) system. A review of the literature showed that an interface caused by a small contrast in densities resulted in a minimum amount of power from a transmitted signal being reflected. The following laboratory study revealed that the minimum amount of this power reflected is capable of causing a printable signal. It is these signals that cause difficulty in distinguishing the desired target in a GPR survey. Thus, the GPR system is often too sensitive for many applications, and it is suggested that some type of signal enhancement be considered for the system.
Electrical Analogy of Hydraulic Flow Through Rock Fractures
Authors: Sundaram PN , Frink D
Published: February 2009

Electrical analogy is used to study the influence of contact areas on the hydraulic flow through rock fractures. The investigation has shown that in the case of radial flow the location of contact zones, as well as the total contact area, influences the flow rate. It is also demonstrated that when injection tests are conducted in boreholes, where the fracture close to the borehole is partially plugged by loose particles or other debris, the flow rate may be substantially underestimated.
A Multi-Purpose Rock Core Testing Device
Authors: Swan G , Olofsson T
Published: February 2009

The need for a multi-purpose rock tester that incorporates a microcomputer for logging and evaluation purposes is identified. A number of semistandard test methods adaptable to such a tester are examined and found suitable from the point of view of simplicity, cheapness, and accuracy of determination. Some design aspects of this tester in its present state of development are considered.
Cyclic Triaxial Tests with Continuous Measurement of Dissipated Energy
Authors: Simcock KJ , Davis RO , Berrill JB , Mullenger G
Published: February 2009

This article describes conventional cyclic triaxial tests on a uniform sand in which the amount of energy dissipated by the specimen was continuously monitored. Energy monitoring was achieved by means of a digital circuit that automatically integrated the force-displacement signals as the test progressed. The resulting energy trace was plotted against the pore pressure buildup within the specimen. From a total of 21 tests, it appears that pore pressure generation and dissipated energy are functionally related, but this relationship appears to depend strongly on the level of cyclic deviator stress.
Drilling and Sampling Frozen Fine-Grained Soils
Authors: Horvath JS , Johnson FW
Published: February 2009

A frozen, moderately plastic clay with a few lenses of shell fragments and sand was successfully sampled using a Denison sampler with a plastic liner. Chilled diesel fuel was used as the drilling fluid. Improvements to this approach are suggested.
Suggested Test Method for Determination of the Soluble Salt Content of Soils by Refractometer
Authors: Chaney RC , Slonim SM , Slonim SS
Published: February 2009

A method suitable for laboratory or field application is proposed to extract pore water from a soil and determine its salinity. The pore water is extracted from the soil using a soil press originally developed by Kriukov and Komarova. Once the pore water has been extracted its salinity is determined using a hand-held refractometer with either a parts per thousand (ppt) or refreaction index scale. Using this method it is possible to measure salinity to an accuracy of ±1 ppt. Notes on sample storage and handling are included.
Burst Tester for Geotextile Bidirectional Strength
Authors: Costa JMA , Raymond GP
Published: February 2009

A burst tester for assessing the bidirectional strength of geotextiles has been developed and is presented herein. The tester was used to determine the properties of a number of differently manufactured geotextiles, and these results are described. The results are analyzed using the theory for membranes subject to a uniform pressure.

Having established the usefulness of the tester for bidirectional strength testing the apparatus was used to assess the resistance of geotextiles to abrasion produced with the standard double-head rotary test in accordance with ASTM Tests for Abrasion Resistance of Textile Fabrics (Oscillatory Cylinder and Uniform Abrasion Method) (D 1175). The effects using different stones are reported on, and the results using an H-18 stone are compared with the field performance of some geotextiles recovered from a railroad track environment. Conclusions are presented favorable to the use of the developed appratus.
Direct Shear Strength of Appalachian Coal
Authors: Peng SS , Patrick CW , Khair AW
Published: February 2009

A total of 142 prismatic specimens were prepared from five different Appalachian coal seams for direct shear-strength tests. Two types of specimen fracture were observed. The shear stress versus shear displacement and normal displacement for each specimen were recorded and analyzed. Two linear regressions were derived to best fit the shear failure of the coal.
Use of a Chain Saw for Obtaining Undisturbed Block Samples
Authors: Tiedemann DA , Sorensen RD
Published: February 2009

High quality undisturbed soil samples can be obtained by hand cutting methods. However, the procedures currently used are tedious, time consuming, and may not yield acceptable results in certain soil types. A procedure using a chain saw with a specially fabricated chain has been developed and field tested. The procedure has been shown to provide quality samples of a variety of materials in much less time than would be required using coventional methods.
Small Cone Penetrometer Tests and Piezocone Tests in Laboratory Consolidated Clays
Authors: Almeida MSS , Parry RHG
Published: February 2009

Small vane, 10-mm-diameter cone penetrometer and 12.7-mm-diameter piezocone devices have been developed to measure soil properties in centrifuge models during flight. This paper presents tests with these devices on kaolin and Gault clay in a normal gravity field. Empirical cone factors were shown to increase with increasing overconsolidation ratio but were found to depend on other factors such as cone size and testing rates. The values also differed considerably between the two clays used. Tests with the small piezocone have shown that the ratio of pore pressure to point resistance decreases slightly with the overconsolidation ratio, but not enough for this ratio be used as a method for determining overconsolidation ratio (OCR). As shown by other workers, pore pressures acting around the tip influence measured tip resistance and should be taken into account when interpreting cone resistances in clays. Dissipation tests with the piezocone have yielded values of coefficient of consolidation agreeing very well with those from swelling tests on clay cakes.
Prediction of Pore-Water Pressure Buildup During Undrained Resonant Column Testing of Virgin Sand Specimens
Authors: Chung RM , Yokel FY
Published: February 2009

Prediction of pore-water pressure buildup of a saturated sand deposit subjected to dynamic load is important for dynamic stability analysis of the deposit. Empirical equations, proposed by Drnevich to correlate the predicted pore-water pressure buildup with that measured during undrained resonant column tests on saturated Ottawa silica sand, were used to predict the results of tests on virgin Monterey No. 0 sand specimens. It was found that, with a modification of the coefficient in the empirical equation, there is good correlation between predicted and measured excess pore-water pressures when a high degree of saturation (B ≥ 0.96) was achieved in the specimen preparation. The correlation is poor for specimens with a lower degree of saturation (B < 0.96).
Methods for Predicting Shale Durability in the Field
Authors: Santi PM , Higgins JD
Published: February 2009

Durability of shales and other weak rock is an important parameter describing the material's susceptibility to breakdown upon exposure to water or during construction work. While laboratory methods have been developed to measure durability, no correlations between laboratory results and simple field tests have been determined.

The results of this study show that certain field parameters can predict slake durability with acceptable accuracy. The recommended field tests, in order of desirability, are slake index, jar slake, hammer rebound, and NGI “Q” value. Single variable and multiple variable linear regression equations are given, including equations conservatively modified so that 95% of the slake durability values are underpredicted.
Application of Bender Elements in Measuring Gmax of Sand Under K Condition
Authors: Zeng X , Ni B
Published: February 2009

A new application of bender elements to measure the small strain shear modulus of sand in multiple shear planes under anisotropic loading is developed. The tests were conducted in a specially designed oedometer with the side of the ring smoothed by a Teflon sheet. The soil used in the tests is clean angular pool filter sand. The effects of size of bender elements on the results of shear wave velocity measurement are discussed. Shear modulus in four different shear planes during a loading-unloading cycle is presented. The results of experiments are compared with the Hardin-Blanford equation on Gmax, which shows good agreement. The influence of side friction of the oedometer is investigated.
Apparatus for Cyclic Stress Path Testing
Authors: Khosla VK , Singh RD
Published: February 2009

A simple change in the conventional cyclic triaxial cell was made to carry out constant mean stress tests on dry Ottawa sand. Test results show that stress-strain characteristics under cyclic loading conditions are significantly affected by the imposed stress path.
Procedure for Determining the Segregation Potential of Freezing Soils
Authors: Konrad J-M
Published: February 2009

Basic frost heave data obtained from various types of laboratory freezing tests, using computerized ramp temperature generation and temperature control at both warm and cold ends of a soil specimen, are analyzed to determine the segregation potential. Automatic volume change measurements provide fair values of cumulative water intake, but not accurate water intake rates. A method based on accurate measurements of total heave, taking into account the amount of heave from in-situ freezing of pore-water, yields relevant freezing characteristics of soils. Precise and automatic acquisition of temperature measurements and of total heave during an open-system freezing test enables accurate definition of the segregation potential, the suction at the frozen-unfrozen interface and the rate of cooling of the frozen fringe, immediately after testing. Examples of freezing test results are given to emphasize the influence of various factors such as the temperature at the segregation-freezing front, the soils porosity, and the unfrozen water content on the segregation potential of freezing soils.
Directional Shear Cell Experiments on a Dry Cohesionless Soil
Authors: Sture S , Budiman JS , Ontuna AK , Ko H-Y
Published: February 2009

The directional shear cell has become an important tool for investigating anisotropic soil behavior, especially effects caused by rotation of principal stress directions during monotonic, cyclic, proportional, and nonproportional loading. This paper describes a newly developed directional shear cell and typical stress-strain response curves from two groups of experiments on a cohesionless soil where the principal stress directions either rotate discretely in a jump-like manner or continuously rotate at constant magnitude. It is shown that stiffness moduli are significantly reduced when principal stresses rotate with respect to the soil fabric and that substantial shear strains occur when principal stresses rotate while their magnitudes remain constant.
A Low-Cost Electrolytic Tiltmeter for Measuring Slope Deformation
Authors: Zhang X
Published: February 2009

The tiltmeter described consists of an electrolytic sensor (a glass jar containing an electrolyte and six electrodes) and a portable AC digital conductivity meter, which reads conductivity changes resulting from tilting deflections. The tiltmeter has a sensitivity of 2 to 8 min of arc/cmu (conductivity meter unit), with a measurement range of more than 45°. This tiltmeter measured earth flow subsurface movements reliably. It was easy to install and read.
Undrained Deformability and Strength Characteristics of Soft Bangkok Clay By the Screw Plate Test
Authors: Bergado DT , Huan NM
Published: February 2009

Eighteen screw plate tests were carried out using 10-in. 25.4-cm diameter plate, and three types of laboratory test were performed, namely, 18 unconfined tests, 31 unconsolidated-undrained triaxial tests, and 18 one-dimensional consolidation tests. The sampling and testing were carried out at three sites inside the campus of the Asian Institute of Technology in the soft clay layer. At each site, six screw plate tests were performed at depths of 2.50, 4.50, and 6.00 m, and three boreholes were made to take 60-cm-long Shelby tube samples at the test levels. The screw plate test results were calibrated with unconsolidated-undrained (UU) triaxial test results and the bearing capacity factor Nc was found to be 11.00 while the undrained modulus factor K was found to be 0.61. The screw plate test results were also correlated with the unconfined compression (UC) test and one-dimensional consolidation test in this study as well as with the vane shear test and pressuremeter test results from previous investigations. Furthermore, the pressuremeter-settlement-time relationship was evaluated, and it was found that the logarithm of settlement rate, log s, decreased linearly with the logarithm of time, log t, and increased linearly with the logarithm of the stress level, log P′.
Liquid Limit Determination—Further Simplified
Authors: Nagaraj TS , Murthy BRS , Bindumadhava
Published: February 2009

In recent years the cone penetration method to determine liquid limit of soils has gained popularity and acceptance. This paper advances two more specific potentials of this method by which (1) the liquid limit can be determined almost instantaneously and (2) the liquid limit of soils, also having particles coarser than 425 µm can be directly determined. The interrelation between water content and bulk density at known degree of saturation and specific gravity of soil solids has been used to compute the water content. In the cone penetrometer method, availability of a cup of standard volume is shown to be helpful in determining the bulk density of the soil for different penetration values. In the range of water contents around liquid limit it is further shown that the degree of saturation of the bulk soil in the cup is around 98%. Using this, the water content at different penetrations can be computed. The floating matrix concept has been used to demonstrate the ability of this method to determine the liquid limit of soils also having particles coarser than 425 µm. The limiting size and percent of coarse particles have been indicated.
Determining Preconsolidation Stress and Penetration Pore Pressures from DMT Contact Pressures
Authors: Mayne PW
Published: February 2009

Over recent years, several geotechnical explorations in clay deposits have shown the flat dilatometer test (DMT) to provide reasonable estimates of in-situ overconsolidation ratio with depth. Why should the horizontal stress index (KD = initial contact pressure minus hydrostatic pressure normalized to the effective overburden stress) show an empirical trend with over consolidation ratio (OCR)? It is postulated that, since the closing pressure and contact pressures are nearly equal, the initial contact pressure in clay is an approximate measure of the total pore pressure induced during penetration of the dilatometer blade. Published data from a clay site tested by a special DMT having a pore-pressure sensor, as well as piezocone/dilatometer data from seven other sites, support this hypothesis. Since the pore-pressure response of clay is influenced by the in-situ OCR, the initial effective DMT contact pressure can be used to profile the stress history.
Chemical Mass Transport Measurements to Determine Flexible Membrane Liner Lifetime
Authors: Lord AE , Koerner RM , Swan RH
Published: February 2009

The prediction of the service life of flexible membrane liners (FMLs) when exposed to chemicals has usually been by way of testing for physical or mechanical property changes after periodic exposure times. This paper presents an alternate approach by evaluating the chemical properties via five different mass transport related measurements of the exposed FML. These tests are water vapor transmission (WVT), radioactive tracer transmission (RT), water absorption (WA), water vapor absorption (WVA), and benzene absorption (BA).

This approach was tested for exposures of up to 15 months. The FMLs used were polyvinyl chloride (PVC), ethylene-propylene-diene monomer (EPDM), chlorinated polyethylene (CPE), and high density polyethylene (HDPE). The chemicals used were 10% sodium hydroxide (NaOH) (in water), 10% sulfuric acid (H2SO4) (in water), 10% phenol (in water), 100% xylene, and water (as a control). The WVT and RT were found to be quite reliable test methods, whereas the WA and WVA techniques experienced serious problems in regard to obeying simple one-dimensional diffusion theory. The BA method worked well for HDPE. The various transport coefficients showed all the expected types of behavior with chemical exposure: (1) constancy with exposure (acids and bases on most all FMLs and all chemicals on HDPE), (2) decrease with exposure (plasticizers leaching from FMLs), and (3) increase with exposure (Phenol-treated CPE). The WVT and RT results were generally complimentary to one another. The transport approach was quite successful in predicting the instability of CPE exposed to phenol. This instability was further verified by differential scanning calorimetry measurements.

The work reported herein lends credence to the use of mass transport measurements to determine structural change in FMLs. Thus the monitoring of transport properties, over a reasonable exposure time to particular chemicals, could serve as the basis for a predictive method for FML lifetime.
Servo-Controlled Cuboidal Shear Device
Authors: Sivakugan N , Chameau J-L , Holtz RD , Altschaeffl AG
Published: February 2009

A servo-controlled cuboidal shear device with automatic data acquisition system is described. Provisions are made for pore-pressure measurements with specially designed “needle” piezometers. Complete stress-strain curves can be obtained with strains up to 20%. The application of servo-control in Ko consolidation and strain controlled loading is illustrated with flow charts and experimental data.
Multistage Direct Shear Testing of Unsaturated Soils
Authors: Gan KJ , Fredlund DG
Published: February 2009

A conventional direct shear box was modified to accommodate the testing of an unsaturated soil. The design concepts and necessary modifications to the apparatus are described. A multistage testing procedure is outlined. Typical results from direct shear tests are presented. The results illustrate the relationship between suction and shear strength for a glacial till soil.
Profiling OCR in Stiff Clays by CPT and SPT
Authors: Mayne PW , Kemper JB
Published: February 2009

Standard penetration tests (SPT) and cone penetration tests (CPT) have conventionally been used to index profiles of undrained shear strength su in clay deposits. Since su is related to stress history, an alternative use of penetration resistances is the profiling of in-situ overconsolidation ratio (OCR). An empirical methodology is developed based on compiled data bases from 50 sites investigated by SPTs and 40 sites tested by CPTs. The study indicates general trends occur between the in-situ OCR and penetration resistances normalized to effective overburden stress in clays. Site specific calibration with laboratory consolidation tests is required, however, for profiling. Electric CPTs are preferable over SPTs and mechanical CPTs for profiling stress history because they are more repeatable and less subject to operator influence.
An Electromagnetic Connection for Triaxial Testing
Authors: de Gijt JG , Pronk WD
Published: February 2009

This paper describes a new tensile connection for transmitting tensile forces to triaxial test specimens. Comparative tests show that the loading and frequency characteristics of this electromagnetic connection are considerably better than those of commercially available screw and vacuum type connections. This means that two-way cyclic triaxial tests can be controlled with much greater precision. Also the procedures for specimen preparation are considerably simplified.
Effect of Dissolved Oxygen (and Bubbles) on the Measured Permittivity of Geotextiles
Authors: Halse YH , Lord AE , Koerner RM
Published: February 2009

Measurements are made of the permittivity in a heat set, nonwoven staple filament polypropylene as a function of the dissolved oxygen content (DOC) of the water. Vacuum deairing of the water to a DOC of 5 ppm or below insures that the measured permittivity will not be lowered by oxygen effects. Careful long-term measurements show that the measured permittivity is reduced very significantly if the DOC rises above 6 ppm. However as long as bubbles are not observed in the water, reasonably good values of the permittivity can usually be achieved, provided the measurements are performed rather quickly.
The Role of Jute Geotextile/Slurry Interface Friction on the Bearing Capacity of Clay Slurry
Authors: Tan S-A , Muhammad N , Karunaratne G-P
Published: February 2009

The layered clay-sand scheme of land reclamation depends on the successful formation of sand seams sandwiched between hydraulically placed layers of marine clay slurry to provide shorter drainage paths for rapid clay consolidation during surcharge application. It is anticipated that a low-cost jute geotextile placed on a clay slurry surface without anchorage will expedite construction of sand seams by providing support for the thin sand layers and preventing penetration of sand into the clay slurry. In this application, the interface friction between the very soft clay slurry and the jute geotextile plays a major role in determining the support for the thin sand seam. This paper discusses measurement of the jute/slurry interface friction by incremental vertical penetration of a thin, end-weighted jute sheet under an incremental load to obtain the interface stress value under a quasistatic condition. The effects of sheet width and sheet type were investigated and found to be negligible on the measured interface friction for the clay slurry water content range tested. The results of the interface friction for the 500 g/m2 jute geotextile is then applied to a rectangular loaded area with a jute base on clay slurries of 150 to 300% water content. These water contents are the likely range of values to be encountered in field applications. The load test results indicate that the measured bearing capacity for the jute on clay slurry is about 5.5 to 6.5 times the interface friction, which is in close agreement with typical bearing-capacity factors used in a shallow foundation on clays.
Model Study on the Failure Mechanism of Soil-Nailed Structure Under Surcharge Loading
Authors: Kim D-S , Juran I , Nasimov R , Drabkin S
Published: February 2009

To investigate the effects of surcharge loading on the failure mechanism of soil-nailed structures, reduced scale-model tests were performed. The main variables for this study were the bending stiffness and tension resistance of nails and applied surcharge loading levels. In addition, two different testing sequences were used to simulate, respectively, the application of soil nailing in both new construction and rehabilitation or widening of earth-retaining systems under surcharge loading. To effectively assess the loading effects on the failure mechanism, failure tests without surcharge loading were performed, and the results were used as reference data. When applying surcharge loading, the failure of the system occurred through a progressive breakage of the nails initiated at the top nails. Under low surcharge loading, the state of stress in the upper nails is close to the stress state for the unloaded wall. As the surcharge loading increases, the equivalent earth pressure coefficient in the upper nails tends to increase toward the atrest value. The locus of nail breakage points under surcharge loading is fairly close to that obtained with flexible nails without surcharge loading regardless of bending stiffness and construction sequence.
Factors Affecting the Performance of a Pneumatic Earth Pressure Cell
Authors: Felio GY , Bauer GE
Published: February 2009

Twenty pneumatic total earth pressure transducers of type SOLINST were installed on a bridge abutment. It was found that their performance was affected considerably by temperature, and to a lesser extent, by the installation procedure and the type of soil in contact with the pressure cells. In order to quantify these influences, an extensive laboratory investigation was undertaken. From this experimental study, correction factors were obtained and applied to the field data. It is suspected that other pneumatic pressure cells will be affected similarly and field measurements need to be corrected.
Imaging of Rock Fractures with Low-Frequency Ultrasonic Reflection/Diffraction
Authors: Glaser SD , Hand MK
Published: February 2009

This paper documents the development of a method for imaging millimeter-scale fractures in rock with low-frequency ultrasound and seismic algorithms developed originally for kilometer-scale geologic structures. Low-frequency ultrasonic reflection/diffraction imaging provides detailed images of an impedance contrast in terms of two-way travel time from the surface to the fracture, which produces a geometrically distorted representation. Several seismic methods were used to sharpen the images, including migration, which greatly enhances horizontal resolution and inverts the image from the travel time domain back into the depth domain. The resulting images allow quantitative analysis of the geometry and location of the fracture.

Computer-based parametric modeling indicates that velocity changes as small as 5% of the rock matrix velocity can be resolved, and fracture length and thickness less than 1 mm can be resolved. Laboratory-scale tests were run on a cast rock-like block with a known flaw (150-mm disk “sandwich” of oil-separated polyethylene, total thickness 1.5 mm). The processed data allowed quantification of the known flaw as well as revealing a sub-millimeter-thick crack that was created during construction of the block. As a final test, the method successfully imaged the failure crack in a rock beam under static loading.
Development of an Axisymmetric Field Simulator for Cone Penetration Tests in Sand
Authors: Hsu H-H , Huang A-B
Published: February 2009

An experimental system capable of simulating axisymmetric field conditions has been developed. This system, as an improvement over conventional calibration chambers, enables cone penetration tests (CPT) to be calibrated under minimal boundary effects. The new simulator consists of a stack of 20 rings to house the sand specimen. These rings are lined with an inflatable silicone rubber membrane on the inside. The boundary expansion and stress are measured and individually controlled, respectively, at each ring level during the CPT. The soil from physical boundary to infinity is simulated using a nonlinear cavity expansion curve derived from a lateral compression test on the specimen. Results from a series of CPTs show that at relative densities of approximately 80%, the cone tip resistance values agree within 4% as the diameter ratio of the physical specimen over cone varies from 18 to 22. This paper describes unique features of this field simulator, presents available CPT data performed in the simulator, and discusses its implications on future calibration tests.