bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory Modeling of Inclined-Loaded Shafts in Sand
Authors: Vidich SD , Kulhawy FH , Trautmann CH
Published: February 2009

Baseline information is presented for preparing and conducting load tests on larger laboratory-scale models of shafts in sand under static and cyclic inclined loading. The shaft models were prefabricated and reusable, with a 52-mm-diameter and depth-to-diameter ratios of 3, 6, and 9. The procedures used for soil deposit preparation in a unique combined sand hopper and testing chamber are presented, along with the testing approaches for static and cyclic loading. Testing was done in uniform deposits of loose and medium dense normally consolidated sand and dense overconsolidated sand. Loads were applied to the shafts at seven load inclinations using a hydraulic actuator system controlled by a mini-computer. For the static tests, loads were applied at a constant displacement rate; for the cyclic tests, loading was force-controlled, and it was applied as a one-way sinusoidal waveform. Measurements of load, displacement, and rotation were taken automatically with transducers linked to a data acquisition system, and important issues in data interpretation are discussed. Typical test results show that: (a) cyclic loading results in slightly stiffer and stronger response than static loading for comparable initial soil conditions, and (b) the accumulated cyclic displacements can be quantified in a straightforward manner.
Commentary on Marchetti Flat Dilatometer Correlations in Soils
Authors: Mayne PW , Martin GK
Published: February 2009

Since its inception in 1975, the flat dilatometer has served as a simple and expedient indexing tool for site stratification and evaluation of soil properties, primarily in North America, Europe, and Southeast Asia. Although the original empirical correlations have proved useful in obtaining approximate parameters for geotechnical analysis and design, the initial statistical trends were based on data from only eleven natural soils, primarily in Italy. A number of comparative studies, modified relationships, and new correlations have since become available in foreign soils, and several of these are reviewed herein. The possibility of adopting generalized expressions for data reduction and the interpretation of soil properties is explored, particularly for evaluating the lateral stress coefficient (K0) in clays from the dilatometer index (KD).
Evaluation Tests for Colloidal Silica for Use in Grouting Applications
Authors: Persoff P , Moridis GJ , Apps JA , Pruess K
Published: February 2009

Colloidal silica (CS) is a low-viscosity chemical grout that can be injected to form an impermeable barrier in the subsurface. Such a barrier was proposed to be placed under a disused unlined retention basin at the Savannah River site. Specifications for the CS grout were included in the bid package, including performance tests. The product must meet requirements of low viscosity, low permeability when gelled, and controllable gel time both in vitro and in situ. Bidders submitted samples for evaluation, and this paper describes the tests that were conducted and presents typical results.

Gel time in soil was assessed by injection tests in packed-soil columns and the monitoring of gelling in the columns. Injection tests were designed to ensure that grout injection would not be impeded by rapid gellation caused by contact with soil. The requirement was that the injection pressure during 2 h of injection be less than 2.5 times as great as the injection pressure without gelling. Gelling of the grout in the soil columns was monitored by repeated falling-head tests that showed that mobility decreased to zero during the prescribed time for gelling in situ.
T Chart to Evaluate Consolidation Test Results
Authors: Tewatia SK , Venkatachalam K , Sridharan A
Published: February 2009

Using Terzaghi's degree of consolidation, U, and the time factor, T, relationship, if MU1 and MU2 (MU1 ≠ MU2) are slopes of the U−√T curve at any two time factors TU1 and TU2, then it can be shown that a unique relationship exists between TU2/TU1, MU1/MU2, and TU1 (or TU2), and knowing any two of these, the third can be uniquely determined. A chart, called the T chart, has been plotted using these three variables for quickly determining T and U at any experimental time, t, to determine the coefficient of consolidation, cv, corrected zero settlement, δ0, and ultimate primary settlement, δ100. The chart can be used even in those cases where settlement and time, at the instant of load increment, are not known.
The Use of Property Tests to Determine the Thermal Properties of Soils
Authors: Salomone LA , Kovacs WD
Published: February 2009

Use of soil as an insulating material and to store and dissipate heat requires that low-cost simple tests be identified to predict the thermal behavior of soils. The optimum moisture content and plastic limit of fine-grained soils were found to correlate with the critical moisture content, that is, the moisture content that defines the knee of the thermal resistivity versus moisture content curve. The laboratory test procedures and equipment that allow these correlations to be made are described.
In-Plane Hydraulic Properties of Geotextiles
Authors: Koerner RM , Bove JA
Published: February 2009

Because of the large number of practical applications using the in-plane hydraulic properties of bulky geotextiles, there exists a need for a suitable test method, which should eventually be standardized. The method developed here measures the parallel flow of water in a constant head device using relatively large rectangular specimens measuring 61.0 by 30.6 cm (24 by 12 in.). The device can support normal stresses on the geotextile up to approximately 144 kPa (3000 lb/ft2).

The basic parameter measured is transmissivity (the in-plane coefficient of permeability times the geotextile's thickness), which behaves as a strongly exponential decreasing function with increasing normal stress. A wide variety of needled nonwoven geotextiles were tested with transmissivity values ranging between 0.062 to 0.14 cm3/s/cm (0.004 and 0.009 ft3/min/ft) fabric. Tests on multiple layers of fabrics showed an increase in transmissivity roughly proportional to the thickness of the total number of layers. When the thickness was eliminated from the transmissivity values, it was seen that the in-plane coefficient of permeability was equivalent to that of a coarse to fine sand and was highest for a single layer of fabric and decreased as the fabric layers increased.

As a final comment, the need for geotextile transmissivity test standardization is noted and highly recommended.
A Method of Estimating the In-Situ Density of Dry Uniformly Graded Sand Under Controlled Conditions of Placement
Authors: Wersching SN , Delpak R , Rowlands GO
Published: February 2009

One of the main problems faced by investigators working with dry sand is the inability to obtain undisturbed specimens from which fundamental soil parameters may be established. The two principal related variables in sand are density and the angle of internal shearing resistance. This paper describes a method of estimating the in-situ sand density from a small specimen of sand, the grains of which are cemented together using plaster. The method uses an unhydrated sand/plaster mixture that is deposited in pockets at strategic locations within the soil profile during its construction. The plaster is subsequently hydrated by the injection of a quantity of water through a small pipe venting at the location of the specimen. Such specimens are retrieved at the end of a test and their densities determined from which the density of the uncemented sand in the proximity of the specimen can be estimated using a relationship previously determined through calibration.
Proposed Standard Test Methods for Cross-Hole Seismic Testing
Authors: Ballard RF , Stokoe KH , McLemore R
Published: February 2009

This paper proposes standard test methods for cross-hole seismic testing. A preferred test method intended for use on critical projects where the highest quality data must be obtained is described, and an optional method intended for use on projects that do not require measurements with the same degree of precision is also presented. Data acquisition equipment, such as seismic sources, receivers, and recording systems, are discussed and various applications of the data addressed, along with acceptable interpretation procedures. Other pertinent items that are addressed include borehole spacing, drilling, casing, grouting, deviation surveys, and actual test conduct. It is noted that a variety of equipment can be used to conduct a satisfactory cross-hole seismic test. As a result, this paper is directed toward the actual test procedure, data interpretation, and specifications for equipment that will yield uniform test results.
Suggested Test Method for Determination of Thermal Conductivity of Soil by Thermal-Needle Procedure
Authors: Chaney RC , Ramanjaneya G , Hencey G , Kanchanastit P , Fang H-Y
Published: February 2009

A method is proposed for determining the thermal conductivity k or thermal resistivity p of soils. The procedure is based on the use of a transient heat method in which a thermal needle is used to create a linear heat source, and a thermocouple is used to monitor temperature changes with time. This suggested method describes the basic procedure. Information is also presented on the construction and calibration of the thermal needle.
Proposed New Standard Test Method for Dimensional and Shape Tolerances of Rock Core Specimens
Authors: Haas CJ
Published: February 2009

The purpose of this proposed standard is to standardize the specifications and procedures for tolerance checks that are required in several ASTM standards involving compression testing of rock core. Some of the material in this standard already appears in ASTM Test for Triaxial Compressive Strength of Undrained Rock Core Specimens Without Pore Pressure Measurements (D 2664), Test for Direct Tensile Strength of Intact Rock Core Specimens (D 2936), Test for Unconfined Compressive Strength of Intact Rock Core Specimens (D 2938), and Test for Elastic Moduli of Intact Rock Core Specimens in Uniaxial Compression (D 3148).
Methods of Evaluating the Expansion Potential of Compacted Soils with Significant Fractions of Large Aggregate
Authors: Houston SL , Vann JD
Published: February 2009

A laboratory investigation of the expansion potential of compacted soils with large-sized aggregate has been conducted. Methods developed for determining expansion potential include (1) laboratory expansion testing of representative specimens containing particles as large as practical and (2) prediction of expansion potential for soils with large-sized aggregate from the results of laboratory expansion tests on minus #4 material. It has been shown that incorporation of up to ¾-in (1.9-cm) material is practical for laboratory expansion tests, with only minor modifications to commonly used swell test equipment.
The Prediction of Fracture Fatigue Parameters from Creep Testing of Soil Cement
Authors: Kim Y , Little DN
Published: February 2009

When a cement-treated base layer is subjected to repeated stress, inherent microcracks begin to propagate and coalesce from the bottom of the layer and finally cause the layer to fail. In order to identify the rate of fatigue failure of the cement-stabilized base layer, Paris' law, da/dN = A(ΔKmax)n, can be used.

In this research, the parameters, A and n, were predicted by a viscoelastic approach. Uniaxial tensile creep tests were performed, and the creep versus time data were represented by means of the generalized power law, D(t) = D0 + D2tm. This power form represents the creep response of soil cement much better than the pure power law, D(t) = D1tm, because of the large initial elastic strain. Schapery's crack growth theory in linear viscoelastic media, based on the classical correspondence principle plus Laplace transform inversion, was utilized to express A and n in terms of measured creep parameters and simple material properties. These predicted parameters were compared with those developed empirically at different cement contents and curing ages. Plots of log A versus n were used to verify the validity of the viscoelastic approach to the fatigue failure criteria.
Cone Penetration of Partially Saturated Sands
Authors: Hryciw RD , Dowding CH
Published: February 2009

A laboratory study of cone penetration through partially saturated sand was conducted. A new method for preparing specimens at various degrees of saturation, which utilizes pressure release from previously carbonated water, is described. In closed water systems, where capillary tensions increase effective confining pressures, penetration resistance was significantly higher than in either dry or saturated conditions. Conversely, in closed-gas systems the penetration resistance was slightly lower than at full saturation.
An Alternative Method for Determining the Membrane Penetration Correction Curve
Authors: Lin H , Selig ET
Published: February 2009

Test results show that the previously used linear relationship between the unit membrane penetration and logarithmic effective confining pressure has limitations at low confining pressure. An alternative method is described, based on a hyperbolic type of curve fitting, which can provide more suitable membrane penetration correction curves for various initial confining pressures. An example is given of triaxial strain path test results corrected using both the logarithmic and hyperbolic methods.
Compaction Control and the Index Unit Weight
Authors: Poulos SJ
Published: February 2009

Procedures for measurement of percent compaction and several related practical issues are discussed. When measuring percent compaction, the “maximum” unit weight should be determined for each field unit weight test or nuclear unit weight measurement because minor differences in gradation and grain shape that are neither visually observable nor apparent from conventional gradation tests can have a significant effect on the “maximum” unit weight. A one-point compaction test should be performed as a minimum in most cases to reduce errors and the number of tests needed, to help focus on the soil type, and to help reduce conflicts with contractors.

It would be very desirable to standardize on the use of only one compaction test for all types of construction control. Use of multiple compaction tests in specifications for various fill types causes confusion in practice without adding any complementary benefit.

ASTM Test Method for Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using 10-lb (4.54-kg) Rammer and 18-in. (457-mm) Drop (D 1557) is the test preferred by the author for controlling fill in dam embankments, building foundations, highways, and other fills and for establishing the degree of compaction of natural soils. Since the “maximum” unit weight is not a true maximum, it is suggested that the value measured with the selected standardized test be referred to as the index unit weight (IUW).

Field unit weight tests for compaction control should be done within one layer, below surface disturbance, and in representative locations. Compaction test procedures for measurement of the index unit weight of clean sands and a discussion of the effects of grain breakage are presented.
The Thawed Strength of Soil Compacted While Frozen: An Introductory Study
Authors: Graham J , Fensury H , Shields DH
Published: February 2009

In the northern United States and in Canada, expensive earthmoving equipment usually stands idle during winter months. Considerable overall economies would result if soil could be excavated, transported, and recompacted while frozen. If engineers are to accept winter operations with frozen soil, the soil after thawing should have a strength that approaches that of the same soil worked while unfrozen. This paper examines the strength of soil that is compacted while frozen and then thawed before shearing and compares it with the strength of the same soil compacted in an unfrozen state and never frozen.

The thawed strength of frozen-while-compacted soil depends on its density, and therefore on the size, shape, and strength of the lumps of frozen soil and on the compactive effort. The influence of density (and indirectly the influence of compactive effort) on a thawed sand, a thawed silt, and a thawed clay are clearly outlined here. Work remains to be done to find the optimum frozen lump size and shape for each soil type and temperature, and then to develop the machinery needed to produce the optimum lumps in the field in winter.
Influence of Apex Angle on Cone Penetration Factors in Clay
Authors: Silvestri V , Fahmy Y
Published: February 2009

The present laboratory study investigates the effect of varying the apex angle on cone penetration resistance in clay. In order to reduce the cost associated with the field sampling of large blocks of sensitive clay, an artificially cemented material was conceived and tested. Steady cone penetration tests were carried out in 200-mm-diameter by 1000-mm-long cylinders of artificial clay. The 10-mm-diameter cones used were characterized by apex angles of 7.5, 15, 18, 22.5, 30, 45, 60, 90, and 180°. Penetration resistance factors Nc were obtained for each cone. The results show that the values of these factors are much larger than those predicted by existing theoretical approaches.
Pile Skin Friction in Sands from Constant Normal Stiffness Tests
Authors: Tabucanon JT , Airey DW , Poulos HG
Published: February 2009

Many interface and sand-to-sand direct shear tests have been performed with a constant normal stiffness to investigate the effects of interface roughness, normal stiffness, soil relative density, initial normal stress, and cyclic displacement amplitude on the soilinterface response. It is demonstrated that the patterns of behavior in these tests are similar to those observed in model pile tests and that the constant normal stiffness (CNS) condition is required to account for the effects of the volume changes that occur as soil adjacent to a pile is sheared. In dense sands that tend to expand in volume when sheared, the shear and normal stresses developed are significantly higher than for constant normal load (CNL) conditions and increase with higher values of normal stiffness. For loose sands that compress when sheared, the stresses are lower than in CNL tests and decrease for higher values of normal stiffness. The CNS tests replicate the reduction in shear stress during displacement-controlled cycling and the subsequent loss of capacity reported for model and full-scale piles. The reduction of skin friction during cycling and the subsequent loss of pile frictional capacity is found to be greatest for loose sands, high normal stiffness, large displacement amplitudes, and rough interfaces.
Measurement of In Situ Density of Sand in a Chamber by Using a Thermal Conductivity Penetrometer
Authors: Singh G , Das BM , Chong MK
Published: February 2009

Reliable in situ testing during soil exploration is of great help to geotechnical engineers in design considerations. This paper describes the theory and the laboratory test results for determination of the density of a sand with a quasi-static penetrometer by measuring its thermal conductivity. Effects of disturbance caused by the penetrometer have been studied. It is shown that it is possible to obtain the density of sand by precalibrating the penetrometer.
Apparatus and Procedure for an In Situ Collapse Test
Authors: Mahmoud HHH , Houston WN , Houston SL
Published: February 2009

Procedures for plate load testing in both shallow pits and at the bottom of a borehole are presented with descriptions of the required apparatus. The procedures were developed for collapsible soils but are expected to be useful for swelling soils as well. A key feature of the new procedures is that the wetted bulb of soil under the plate is controlled and its depth is measured at the end of the test. This makes it possible to limit the range of strains in the wetted zone and to calculate the average strain. Research by the authors presented elsewhere led to the development of influence factors that allow computation of the average stress in the wetted zone. The average stress versus average strain derived from the test for the wetted condition is of the same form as that derived from a laboratory collapse test. The in situ collapse tests presented possess certain advantages over lab tests including (a) lesser disturbance effects, (b) the ability to test difficult-to-sample soils, and (c) a degree of wetting likely to be close to that achieved in the prototype. The required apparatus is simple and can be constructed at low cost by most geotechnical firms.
Investigation of Vibration-Induced Settlement Using Multifactorial Experimental Design
Authors: Kim D-S , Drabkin S
Published: February 2009

A prediction model of vibration-induced settlement on granular soils was developed using multifactorial experimental design (MED). Major factors affecting vibration-induced settlement such as vibration amplitude, deviatoric stress, confining pressure, soil gradation, duration of vibration, moisture content, and relative density were considered in this study.

To accommodate all these factors, a special vibratory frame was designed to shake a soil specimen within a triaxial cell. MED allowed the authors to investigate the effect of many factors affecting vibration-induced settlement using a relatively small number of experiments. Detailed procedures for applying MED are discussed.

Low to medium vibration amplitudes with peak particle velocities ranging from 2.5 to 18 mm/s were evaluated for the settlement potential assessment. The most significant factors affecting vibration-induced settlement were vibration amplitude, confining pressure, and deviatoric stress. At a given vibration amplitude, the settlement was substantially reduced with increasing confining pressure. Vibration-induced settlement was affected by the stress anisotropy, and maximum settlement occurred at a given confining pressure in the range of earth pressure coefficients between 0.45 and 0.6.
A New Fall Cone Device for Measuring the Undrained Strength of Very Weak Cohesive Soils
Authors: Zreik DA , Ladd CC , Germaine JT
Published: February 2009

A new fall cone device capable of measuring undrained shear strength of extremely soft cohesive soils is described and evaluated. The Automated MIT Fall Cone has a unique mechanical counterweight system that enables the use of effective cone weights as low as 0.005 N. This weight is an order of magnitude lower than possible with a standard fall cone apparatus. The new device also uses a data acquisition system to record cone penetration versus time throughout the test. An extensive experimental program was performed on a remolded marine clay (Boston Blue Clay) to evaluate the new fall cone apparatus. The program includes measurements of cone velocity and penetration to study the dynamics of the new device. The cone velocities and penetration times agree with theoretical predictions that account for the inertia of the counterweight system. The experimental program includes strength measurements using various cone weights and geometries to check the validity of the strength-penetration relationships over a wide range of liquidity index values (0.75 to 5.6).
Soil Air Permeability: Threshold Gradient and Anisotropy
Authors: Sinha N , Rodeck SA , Omar MT , DeVantier BA , Das BM
Published: February 2009

In this study, a triaxial confinement chamber and mass flow meter were used to measure the air permeability of compacted clayey sand specimens. Specimens were extracted at different angles with respect to the vertical direction to measure the anisotropy. The soil was compacted at high water contents below the optimum.

At lower gradients, deviations from Darcy's law were observed. Threshold gradients were found below which the flow rate-gradient relationship was nonlinear and flow was very small. Measurements of anisotropy in air permeability revealed an order of magnitude difference in permeabilities of the specimens extracted at 0 and 90° with respect to the direction of compaction. The square root of permeability varied in the principal directions according to an ellipse function, although there was significant scatter about the ellipse. The air permeability values obtained from these tests were consistent with previously published results.
Effect of Boundary Conditions Upon Centrifuge Experiments Using Ground Motion Simulation
Authors: Whitman RV , Lambe PC
Published: February 2009

Two containers were used to hold a simulated stratum of sand during dynamic base shaking experiments aboard a centrifuge: a stack of rings and a box with rigid walls. Criteria for a satisfactory stacked-ring device are discussed, and details are presented for the design adopted. Results from several series of tests using stacked rings with different dimensions and aspect ratios are examined. While the overall performance of the stacked-ring confinement is satisfactory, there is evidence of deviations from the condition of simple shear, and also of arching. Almost certainly the rings did not exactly follow the motions of the soil. A few results are presented from tests using a box as the soil container. There is evidence that even distant walls can influence results when liquefaction phenomena are being observed.
Characteristic Threshold and Infrared Vibrothermography of Sand
Authors: Luong MP
Published: February 2009

Rheological properties of granular soils under vibratory, cyclic, and transient loading can be interpreted at the grain level where the solid particles interact with one another. Macroscopic deformations result mainly from the principal following mechanisms: (1) compaction mechanism that forces the solid particles closer together and leads to a denser packing; (2) distortion mechanism governed by irreversible grain slidings generating heat; and (3) attrition mechanism caused by breakage of asperities and crushing of grains under high pressures.

The infrared vibrothermography used in our laboratory is a nondestructive test that allows records and observations in real time of heat patterns produced by the dissipation of energy caused by friction between grains. Such dissipative heat occurs when granular soil is subjected to vibratory loading exceeding the characteristic threshold, and it shows with evidence the distortion mechanism.

The infrared thermographic technique described, which couples mechanical and thermal energy, offers the potential of directly monitoring the stress state of particle rearrangement or characteristic threshold and predicting the macroscopic mechanical response of granular materials.
Suggested Method for Performing the Flat Dilatometer Test
Authors:   ASTM Subcommittee 18.02
Published: February 2009

The ASTM Committee D18.02 on Sampling and Related Field Testing for Soil Investigation, with Mr. Ralph Brown as Chairman, requested that this proposed Standard Method be published herein to provide exposure and to solicit comments from users. The objective is to improve its accuracy, usefulness, and acceptability, when in the future, Committee D18.02 hopes to submit it for publication in the ASTM Book of Standards. Comments should be sent to John H. Schmertmann, Chairman Committee D18.02.10. The Committee will consider all critical comments that include specific suggestions for improving the accuracy, usefulness, or acceptability of the proposed method.
New Equipment and Techniques for Use with the Cambridge Self-Boring Pressuremeter
Authors: Davidson JL , Bloomquist DG
Published: February 2009

New equipment and techniques for use with the Cambridge self-boring pressuremeter have been developed. These include a trailer mounted rig, which supports and transports all the equipment necessary to penetrate the self-boring pressuremeter to test depth, a self-casing technique for use in cohesionless soils where there is a danger of borehole collapse, a portable cassette unit for recording field data and dumping to a main computer, and a data reduction program.
Assessment of Damage to Geomembrane Liners by Shredded Scrap Tires
Authors: Reddy KR , Saichek RE
Published: February 2009

This paper presents the results of a field and laboratory study performed to assess damage to the geomembrane liner caused by using shredded scrap tires as a leachate drainage layer material in landfills. The field testing was performed to assess the damage that occurred to the geomembrane liner during construction and included nine tests conducted with different combinations of tire chip size and thickness, both with a geotextile and without a geotextile overlying the geomembrane, and under different loading conditions. The laboratory testing was performed to characterize the shredded tires, particularly their size distribution, hydraulic conductivity, compressibility, and chemical resistance. The laboratory testing also included performing simulation testing to determine the extent of damage that occurs to the geomembrane liner by the shredded tires under long-term waste-loading conditions. The damage that occurred to the geomembrane liners in both field tests and simulated laboratory tests was determined by visual observations as well as by conducting multi-axial tension tests, wide strip tension tests, and water vapor transmission tests on the exhumed geomembrane samples. Based on these results, a 0.46-m (18-in.)-thick layer of secondary shred tire chips, with an average size of 7.6 cm, placed over a 543-g/m2 (16-oz/yd2) geotextile installed over a geomembrane liner using low-ground-pressure (<58 kPa) equipment was determined to provide adequate protection to the geomembrane liner during construction. The degree of protection offered under long-term loading conditions depends on the normal stress and the random orientation of the shredded tire chips at the geomembrane interface.
Constant Volume Ring Shear Apparatus
Authors: Stark TD , Contreras IA
Published: February 2009

The paper describes a constant volume ring shear apparatus that allows the measurement of the undrained peak and residual shear strengths of cohesive soils. The undrained peak and residual strengths are applicable to seismic stability evaluations of slopes comprised of or founded on cohesive soil. The constant-volume ring shear apparatus is equipped with a mechanism to adjust the normal stress during shear and a new specimen container that allows undisturbed specimens to be trimmed directly into the container. The normal stress is adjusted during shear such that the height of the soil specimen remains constant. This results in a constant volume or undrained shear condition. The results of constant volume ring shear tests on normally consolidated Drammen clay are compared with the results of undrained direct simple shear tests. The comparison reveals that the undrained peak shear strength obtained using the constant volume ring shear and direct simple shear apparatuses are in agreement. However, the constant-volume ring shear apparatus allows the measurement of the undrained residual strength because it permits unlimited continuous shear displacement.
On Large-Scale Model Testing of Laterally Loaded Drilled Shafts in Sand
Authors: Agaiby SW , Kulhawy FH , Trautmann CH
Published: February 2009

An extensive large-scale laboratory model testing program was developed to assess the behavior of drilled shafts under lateral and moment loading. Because of the large scale of the testing, little information was available in the literature on sand deposit and test preparation or on test conduct and monitoring. In this paper, guidance is presented on these preparation and testing issues, and typical results are presented to illustrate the variability of the test results.
Advances in Conductometric Phase Transition Porosimetry
Authors: Gunnink BW
Published: February 2009

The paper describes advances in conductometric phase transition porosimetry (CPTP) test methods and procedures for measuring the pore size distribution of soil. Included are test methods and procedures for (1) measuring the “throat or neck” size distribution using CPTP cooling data, (2) measuring soil pore structure anisotropy using radial and axial CPTP test cells, and (3) measuring the pore size distribution of soil saturated with saline pore water. Test results are presented and discussed for each of these three advances. Some of the advantages of CPTP are that: (1) it is not necessary to dry specimens prior to testing, (2) it is possible to test relatively large specimens, (3) it is possible to investigate pore structure anisotropy, and (4) it is possible to measure the pore size distribution of specimens saturated with a variety of solutions. Some disadvantages are that: (1) saturation of specimens must be 100%, (2) pore size distribution is relative, thus an independent measure of total porosity in necessary, (3) maximum measurable pore size is about 1 μm, and (4) testing time is relatively long, about two days.
Laboratory Evaluation of Horizontal Stress in Overconsolidated Sands
Authors: Abdi H , Garga VK
Published: February 2009

This paper describes a method for the determination of in situ horizontal stresses of heavily overconsolidated sands using a stress-path triaxial apparatus. This method was proposed by Garga and Khan (1991), who applied it to overconsolidated clays. The proposed method is based on the concept that if the radial stress exceeds the in situ horizontal stress while maintaining the axial stress constant and equal to the in situ vertical effective stress, only then will the specimen experience significant axial strain.

In this investigation, the above method was applied to specimens of known stress histories of overconsolidated sand. Simulation of complex stress histories was carried out by subjecting the soil specimens to one and two cycles of loading in drained conditions (rate of loading or unloading: 0.05 kPa/min). It was found that the proposed method replicated the simulated in situ horizontal stress exactly. The technique is capable of estimating K0 irrespective of the previously imposed stress history.
Comparison of Gas and Water Pycnometry of Coal Mine Wastes
Authors: Morris PH , Williams DJ
Published: February 2009

Coal mine washery wastes comprise two major components whose specific gravities differ markedly. Consequently, their specific gravity is much more variable than that of natural soils and is determined relatively frequently. The specific gravity of coal mine wastes is determined more rapidly and efficiently by gas pycnometry than by water pycnometry. However, the two methods give significantly different results. Results of specific gravity determinations for washery wastes from Goonyella Coal Mine in central Queensland, Australia, by gas and water pycnometry, are compared. The differences between them are shown to arise from the pore structure and particle sizes of the wastes and the interaction between the internal surface of the wastes and the pycnometric fluids.
Determination of Ionic Strength and Equilibrium Concentrations of Heavy Metals by the Electrical Conductivity Method
Authors: Kayyal MK , Mohamed AMO
Published: February 2009

A laboratory investigation of several types of heavy metal-soil solutions was conducted to evaluate the possibility of determining ionic strength and equilibrium concentrations of heavy metals and exchangeable cations by means of the electrical conductivity method. The characteristics of the heavy metal-soil interactions including retention of metals and release of exchangeable cations by the illitic soil were examined, and electrical conductivity and pH measurements of the heavy metal-soil solutions were performed. Test results revealed that direct determination of equilibrium concentrations of certain ionic species could be realized by means of electrical conductivity measurements of soil suspensions. This laboratory technique is based on determining the relationship between the ionic strengths of the heavy metal-soil solutions and their electrical conductivity in order to derive the necessary correlations to estimate the equilibrium concentrations. The proposed technique is expected to aid in the direct calculation of equilibrium concentrations of metal ions and heavy metals from data collected during site investigation for remedial activity via electric conductivity or soil resistivity techniques.
Determination of Shear Strength Parameters of Unsaturated Silts and Sands Based on the Water Retention Curve
Authors: Öberg AL , Sällfors G
Published: February 2009

Great efforts have been made to understand and determine the stress parameters of unsaturated soils. However, this requires elaborate laboratory tests, which are both difficult and time consuming to perform. A hypothesis for determination of the shear strength of unsaturated soils is suggested. The hypothesis suggests a simple way of determining the shear strength based on the water retention curve and the angle of internal friction. Values of shear strengths have been taken from the literature and compared with shear strengths calculated according to this hypothesis. The shear strengths obtained from the hypothesis are in surprisingly good agreement with those found in the literature. The suggested hypothesis is critically examined and its limitations discussed. Finally, a reasonable way of applying the hypothesis in engineering practice is proposed.
Equipment for One-Dimensional Compression and Triaxial Testing of Unsaturated Granular Soils at Low Stress Levels
Authors: Anderson WF , Goodwin AK , Pyrah IC , Salman TH
Published: February 2009

This paper describes the design of equipment for examining the behavior of unsaturated granular soils at low stress levels. The one-dimensional compressibility is examined in a 254-mm-diameter compression cell whose unique features include the measurement and control of low-level stresses using load cells incorporated in the loading platen and the ability to determine suctions at the base and top of the specimen. Stiffness and strength behavior is examined in a new double wall triaxial cell that allows accurate determination of the volume change of the 150-mm-diameter unsaturated specimen. Facilities are incorporated in the cell for monitoring axial and radial strains on the central portion of the specimen. A technique for preparing compacted specimens without damaging the brittle high-entry ceramics in the base plates of the cells is described. The performance of the new equipment is discussed, and results of repeatability tests are reported.
Congenital Hypomyelinating Neuropathy with Lethal Conduction Failure in Mice Carrying the Egr2 I268N Mutation
Authors: Baloh Robert H. , Strickland Amy , Ryu Elizabeth , Le Nam , Fahrner Timothy , Yang Mao , Nagarajan Rakesh , Milbrandt Jeffrey
Published: February 2009

Mouse models of human disease are helpful for understanding the pathogenesis of the disorder and ultimately for testing potential therapeutic agents. Here, we describe the engineering and characterization of a mouse carrying the I268N mutation in Egr2, observed in patients with recessively inherited Charcot–Marie–Tooth (CMT) disease type 4E, which is predicted to alter the ability of Egr2 to interact with the Nab transcriptional coregulatory proteins. Mice homozygous forEgr2I268Ndevelop a congenital hypomyelinating neuropathy similar to their human counterparts.Egr2I268Nis expressed at normal levels in developing nerve but is unable to interact with Nab proteins or to properly activate transcription of target genes critical for proper peripheral myelin development. Interestingly,Egr2I268N/I268Nmutant mice maintain normal weight and have only mild tremor until 2 weeks after birth, at which point they rapidly develop worsening weakness and uniformly die within several days. Nerve electrophysiology revealed conduction block, and neuromuscular junctions showed marked terminal sprouting similar to that seen in animals with pharmacologically induced blockade of action potentials or neuromuscular transmission. These studies describe a unique animal model of CMT, whereby weakness is due to conduction block or neuromuscular junction failure rather than secondary axon loss and demonstrate that the Egr2–Nab complex is critical for proper peripheral nerve myelination.
TORC1 Regulates Activity-Dependent CREB-Target Gene Transcription and Dendritic Growth of Developing Cortical Neurons
Authors: Li Shuai , Zhang Chi , Takemori Hiroshi , Zhou Yang , Xiong Zhi-Qi
Published: February 2009

CREB-target gene transcription during neuronal excitation is important for many aspects of neuronal development and function, including dendrite morphogenesis. However, the signaling events that regulate cAMP response element-binding protein (CREB)-mediated gene transcription during dendritic development are not well understood. Herein we report that the CREB coactivator TORC1 (transducer of regulated CREB 1) is required for activity-dependent CREB-target gene expression and dendrite growth in developing cortical neurons. Ca2+influx via voltage-gated calcium channels induced TORC1 dephosphorylation and translocation into the nucleus in a calcineurin-dependent manner. Nuclear accumulation of TORC1 initiated the expression of CREB-target genes, including salt-inducible kinase 1 (SIK1). In response of persistent depolarization,de novoSIK1 protein in turn promoted TORC1 phosphorylation and consequent depletion of nucleus-localized TORC1. SIK1 induction thus appears to act as a negative feedback signal that prevents persistent CREB/TORC1-dependent transcription in the face of long-lasting neuronal activity. Overexpressing wild type TORC1 promoted basal as well as activity-induced dendritic growth, whereas expressing a dominant-negative form of TORC1 or downregulating TORC1 inhibited activity-dependent dendritic growthin vitroandin vivo. Together, these results suggest that neuronal activity-dependent dendritic growth in developing cortical neurons relies on transient TORC1-mediated CREB-target gene transcription.
A Dual Role for the Adaptor Protein DRK inDrosophilaOlfactory Learning and Memory
Authors: Moressis Anastasios , Friedrich Anke R. , Pavlopoulos Elias , Davis Ronald L. , Skoulakis Efthimios M. C.
Published: February 2009

Participation of RAS, RAF, and mitogen-activated protein kinase (MAPK) in learning and memory has been demonstrated in a number of studies, but the molecular events requisite for cascade activation and regulation have not been explored. We demonstrate that the adapter protein DRK (downstream of receptor kinase) which is essential for signaling to RAS in developmental contexts, is preferentially distributed in the adult mushroom bodies, centers for olfactory learning and memory. We demonstrate thatdrkmutant heterozygotes exhibit deficits in olfactory learning and memory, apparent under limited training conditions, but are not impaired in sensory responses requisite for the association of the stimuli, or brain neuroanatomy. Furthermore, we demonstrate that the protein is required acutely within mushroom body neurons to mediate efficient learning, a process that requires RAF activation. Importantly, 90 min memory remained impaired, even after differential training yielding equivalent learning in animals with compromised DRK levels and controls and did not require RAF. Sustained MAPK activation is compromised indrkmutants and surprisingly is negatively regulated by constitutive RAF activity. The data establish a role for DRK inDrosophilabehavioral neuroplasticity and suggest a dual role for the protein, first in RAF activation-dependent learning and additionally in RAF-inhibition dependent sustained MAPK activation essential for memory formation or stability.
Olig2+Precursors Produce Abducens Motor Neurons and Oligodendrocytes in the Zebrafish Hindbrain
Authors: Zannino Denise A. , Appel Bruce
Published: February 2009

During development, a specific subset of ventral spinal cord precursors called pMN cells produces first motor neurons and then oligodendrocyte progenitor cells (OPCs), which migrate, divide and differentiate as myelinating oligodendrocytes. pMN cells express the Olig2 transcription factor and Olig2 function is necessary for formation of spinal motor neurons and OPCs. In the hindbrain and midbrain, distinct classes of visceral, branchiomotor and somatic motor neurons are organized as discrete nuclei, and OPCs are broadly distributed. Mouse embryos deficient for Olig2 function lack somatic motor neurons and OPCs, but it is not clear whether this reflects a common origin for these cells, similar to spinal cord, or independent requirements for Olig2 function in somatic motor neuron and OPC development. We investigated cranial motor neuron and OPC development in zebrafish and found, using a combination of transgenic reporters and cell type specific antibodies, that somatic abducens motor neurons and a small subset of OPCs arise from commonolig2+neuroepithelial precursors in rhombomeres r5 and r6, but that all other motor neurons and OPCs do not similarly develop from shared pools ofolig2+precursors. In the absence ofolig2function, r5 and r6 precursors remain in the cell cycle and fail to produce abducens motor neurons, and OPCs are entirely lacking in the hindbrain. These studies, therefore, reveal both common and independent roles forolig2in development of somatic motor neurons and oligodendrocytes of the hindbrain.
Dopamine-Dependent Periadolescent Maturation of Corticostriatal Functional Connectivity in Mouse
Authors: Galiñanes Gregorio L. , Taravini Irene R. E. , Gustavo Murer M.
Published: February 2009

Altered corticostriatal information processing associated with early dopamine systems dysfunction may contribute to attention deficit/hyperactivity disorder (ADHD). Mice with neonatal dopamine-depleting lesions exhibit hyperactivity that wanes after puberty and is reduced by psychostimulants, reminiscent of some aspects of ADHD. To assess whether the maturation of corticostriatal functional connectivity is altered by early dopamine depletion, we examined preadolescent and postadolescent urethane-anesthetized mice with or without dopamine-depleting lesions. Specifically, we assessed (1) synchronization between striatal neuron discharges and oscillations in frontal cortex field potentials and (2) striatal neuron responses to frontal cortex stimulation. In adult control mice striatal neurons were less spontaneously active, less responsive to cortical stimulation, and more temporally tuned to cortical rhythms than in infants. Striatal neurons from hyperlocomotor mice required more current to respond to cortical input and were less phase locked to ongoing oscillations, resulting in fewer neurons responding to refined cortical commands. By adulthood some electrophysiological deficits waned together with hyperlocomotion, but striatal spontaneous activity remained substantially elevated. Moreover, dopamine-depleted animals showing normal locomotor scores exhibited normal corticostriatal synchronization, suggesting that the lesion allows, but is not sufficient, for the emergence of corticostriatal changes and hyperactivity. Although amphetamine normalized corticostriatal tuning in hyperlocomotor mice, it reduced horizontal activity in dopamine-depleted animals regardless of their locomotor phenotype, suggesting that amphetamine modified locomotion through a parallel mechanism, rather than that modified by dopamine depletion. In summary, functional maturation of striatal activity continues after infancy, and early dopamine depletion delays the maturation of core functional capacities of the corticostriatal system.