bluuebunny/crossref_metadata_2025 huggingface dataset:
2′-O-methylation stabilizes Piwi-associated small RNAs and ensures DNA elimination in Tetrahymena
Authors: Kurth Henriette M. , Mochizuki Kazufumi
Published: February 2009

Small RNAs ∼20–30 nucleotides (nt) in length regulate gene expression at the transcriptional and post-transcriptional levels. In the plant Arabidopsis, all small RNAs are 3′-terminal 2′-O-methylated by HEN1, whereas only a subset of small RNAs carry this modification in metazoans. This methylation is known to stabilize small RNAs, but its biological significance remains unclear. In the ciliated protozoan Tetrahymena thermophila, two classes of small RNAs have been identified: RNAs ∼28–29 nt long (scnRNAs) that are expressed only during sexual reproduction, and constitutively expressed ∼23–24 nt siRNAs. In this study, we demonstrate that scnRNAs, but not siRNAs, are 2′-O-methylated at their 3′ ends. The Tetrahymena HEN1 homolog Hen1p is responsible for scnRNA 2′-O-methylation. Loss of Hen1p causes a gradual reduction in the level and length of scnRNAs, defects in programmed DNA elimination, and inefficient production of sexual progeny. Therefore, Hen1p-mediated 2′-O-methylation stabilizes scnRNA and ensures DNA elimination in Tetrahymena. This study clearly shows that 3′-terminal 2′-O-methylation on a selected class of small RNAs regulates the function of a specific RNAi pathway.
Rejoinder—Response to Comments on “Website Morphing”
Authors: Hauser John R. , Urban Glen L. , Liberali Guilherme , Braun Michael
Published: February 2009

Website morphing draws on the Expected Gittins’ solution to a partially observable Markov process, on the rapid consumer-segment updating with Bayesian methods, and on matching a website’s look and feel to a visitor’s cognitive style. In each area there are exciting research opportunities including optimality in the presence of switching costs (within a visit), Bayesian updating of cognitive styles across websites, extensions to other segmentation schemes such as cultural styles, morphing of other website characteristics such as advertising, and applications to other media such as smartphones.
A Mathematical Logic Approach for the Transformation of the Linear Conditional Piecewise Functions of Dispersion-and-Store and Cell Transmission Traffic Flow Models into Linear Mixed-Integer Form
Authors: Pavlis Yannis , Recker Will
Published: February 2009

The modeling of traffic control systems for solving such problems as surface street signalization, dynamic traffic assignment, etc., typically results in the appearance of a conditional function. For example, the consistent representation of the outflow discharge at an approach of a signalized intersection implies a function that is conditional on the signal indication and the prevailing traffic conditions. Representing such functions by some sort of constraint(s), ideally linear, so as to be considered in the context of a mathematical programming problem, is a nontrivial task, most often resolved by adopting restrictive assumptions regarding real-life process behavior. To address this general problem, we develop two methodologies that are largely based on analogies from mathematical logic that provide a practical device for the transformation of a specific form of a linear conditional piecewise function into a mixed integer model (MIM), i.e., a set of mixed-integer linear inequality constraints. We show the applicability of these methodologies to transforming into a MIM virtually every possible conditional piecewise function that can be found when one is modeling transportation systems based on the widely adopted dispersion-and-store and cell transmission traffic flow models, as well as to analyzing existing MIMs for identifying and eliminating redundancies.
Children's interpretive understanding, moral judgments, and emotion attributions: Relations to social behaviour
Authors: Malti Tina , Gasser Luciano , Gutzwiller‐Helfenfinger Eveline
Published: February 2009

The study investigated interpretive understanding, moral judgments, and emotion attributions in relation to social behaviour in a sample of 59 5‐year‐old, 123 7‐year‐old, and 130 9‐year‐old children. Interpretive understanding was assessed by two tasks measuring children's understanding of ambiguous situations. Moral judgments and emotion attributions were measured using two moral rule transgressions. Social behaviour was assessed using teachers' ratings of aggressive and prosocial behaviour. Aggressive behaviour was positively related to interpretive understanding and negatively related to moral reasoning. Prosocial behaviour was positively associated with attribution of fear. Moral judgments and emotion attributions were related, depending on age. Interpretive understanding was unrelated to moral judgments and emotion attributions. The findings are discussed in regard to the role of interpretive understanding and moral and affective knowledge in understanding children's social behaviour.
Regulatory mode preferences for autonomy supporting versus controlling instructional styles
Authors: Pierro Antonio , Presaghi Fabio , Higgins Tory E. , Kruglanski Arie W.
Published: February 2009

Background Three studies carried out in educational settings examined determinants of teacher's instructional styles and students' degree of satisfaction with the learning climates created by such styles.

Aims Based upon regulatory mode theory, Studies 1 and 2 tested the hypotheses that teachers' locomotion orientation will be positively related, and their assessment orientation will be negatively related, to autonomy supportive (vs. controlling) instructional styles. Study 3 tested the hypothesis that students' regulatory mode will exhibit a fit effect with the prevalent learning climate in their school.

Samples Participants for Study 1 were 378 teachers (278 females); for Study 2 were 96 teachers (65 females); and for Study 3 were 190 students (all males).

Method Participants completed questionnaires that included measures of teaching styles (Studies 1 and 2), perceived learning climate and satisfaction (Study 3), and regulatory mode orientations (Studies 1 and 3). In Study 2 regulatory mode orientations were experimentally induced.

Results Results confirmed that teachers' autonomy supportive versus controlling styles were positively related to their locomotion orientations and negatively related to their assessment orientation, and that students with a stronger locomotion (vs. assessment) orientation reported a higher level of satisfaction when the learning climate was perceived as autonomy supportive (vs. controlling).

Conclusions The present studies show that teachers' preference for adopting an instructional style is influenced by their regulatory mode orientations, and that the effects of a learning climate on students' satisfaction are contingent on a fit between type of learning climate and students' regulatory mode orientations.
Determination of Collapse Potential of Soils
Authors: Lutenegger AJ , Saber RT
Published: February 2009

A review of various criteria that have been proposed to identify collapsible soils and test techniques, which are used to quantify the amount of collapse, is presented. The results of a series of laboratory single and double oedometer collapse tests conducted on three metastable loess soils are presented to illustrate problems associated with investigating collapse behavior of soils. Guidelines are proposed for developing a standard test procedure.
Helical Probe Tests: Initial Test Calibration
Authors: Yokel FY , Mayne PW
Published: February 2009

Helical test probes of different sizes suitable for shallow (1.8-m) in-situ soil exploration and compaction control were developed and tested in different soils alongside traditional in-situ tests, including Standard Penetration tests (SPT), cone penetration tests (CPT), dilatometer tests (DMT), and in-situ density tests. The helical probe test (HPT) is a quick and economical test, which can be performed by a single person in less than 10 min, making it very attractive for construction field testing on geotechnical projects. The torque necessary to insert the probe is used as a measure of soil characteristics. Preliminary studies indicate that the HPT test correlates well with the SPT test and the correlation is not sensitive to the soil type (particle size); the HPT test correlates well with the CPT test, but the correlation is sensitive to the soil type; and the HPT/SPT and HPT/CPT correlations are consistent with existing data on SPT/CPT correlations. After site calibration, the HPT torque can be used to estimate relative compaction and in-situ density of compacted soils.
Effect of Testing Procedure in Ring Shear Tests
Authors: Anderson WF , Hammoud F
Published: February 2009

This technical note describes a comparison between the results obtained from single-stage and multistage ring shear tests on two different types of normally consolidated clay. The results confirm the brittle behavior of normally consolidated soils containing a high proportion of clay particles and the curved nature of the residual stress failure envelope. Detailed examination of the test data shows that while the multistage technique offers a considerable advantage in terms of the test duration, it may give erroneous results for soils with a high proportion of platy clay particles.
The Behavior at the Shrinkage Limit of Clay Undergoing Drying
Authors: Williams DJ , Sibley JW
Published: February 2009

In this paper, possible links between the shrinkage limit and distinct changes in other properties of a clay soil undergoing drying are discussed. These properties include the volumetric air content of the soil, the heat of wetting, the tensile strength, the total suction, and the thermal resistivity of the soil. The distinct changes are of interest in themselves, and possible explanations for them are briefly discussed. For soil under extremely dry conditions, more importance should perhaps be attached to using the shrinkage limit as an index to changes in soil behavior, and this topic warrants further research.
Techniques for Estimating the Longevity of Lime-Treated Expansive Clays
Authors: McCallister LD , Petry TM
Published: February 2009

Two techniques are presented that investigate the possibility of estimating the longevity of lime-treated expansive clays subjected to leaching. The techniques are based on analyzing calcium concentrations and pH changes within accelerated leached laboratory specimens and their leachates during the leaching process. The accelerated leach times required to produce specific calcium concentrations and pH in the laboratory are converted to actual field leaching (or percolation) times by using developed time scale factors.

The techniques are tested for validity by correlating estimated calcium concentrations and pH values of field lime-treated clays to the actual results of field lime-treated clay layers of various known ages. The correlations showed that pH estimations were within an average of 13% of measured values, while estimated calcium concentrations remaining in the soil-lime layers were within an average of 18% of measured values.
Hollow Cylinder Specimen Preparation: Cohesive Materials
Authors: Crockford WW , Sousa J
Published: February 2009

Techniques for rapid and precise fabrication of hollow cylinder specimens of cohesive materials are presented. A device to accelerate the displacement sensor mounting process is described.
Membrane Penetration in Triaxial Tests
Authors: Boháč J , Feda J
Published: February 2009

Volumetric deformations of triaxial specimens of sand measured with a burette are burdened with an error caused by a rubber membrane penetrating into the peripheral voids of the specimen. This effect is of the same order of magnitude as volumetric deformation of the soil skeleton and should be eliminated. To this end, a method has been proposed based on the K0-stress path. Membrane penetration for the particular material has been approximated by logarithmic and hyperbolic curves. The resulting correction considerably surpasses most published expressions because the latter usually do not consider the porosity of specimens.
Incinerator Residue for Roads
Authors: Aziz MA , Ramaswamy SD
Published: February 2009

A study was conducted by the authors to assess the feasibility of using incinerator residue in road construction. Residues from Singapore incinerators were characterized. Various combinations of mixes comprising local clayey-silty-sandy soil and incinerator residue with or without lime were tested for their suitability for use as road subbase/subgrade. Also, bituminous mixes comprising varying proportions of incinerator residue and granitic aggregates were tested to determine their suitability in road surfacings. This study has revealed that the incinerator residue, although inferior in quality as compared to granitic aggregates for use in dense bituminous mixes for road surfacings, has properties that justify applications in areas where high-quality aggregate is not required. The road subgrade soils can be economically stabilized by using an admixture of incinerator residue from 50 to 75% along with as low as 2.5 to 5% lime. For bituminous mixes, the optimum binder requirement of 10 to 12% makes it quite expensive. However, the use of incinerator residue as unbound base or subbase material with or without blending with natural aggregates is feasible. The incinerator residue also has the potential for use as a free-draining friction course using only 4 to 5% bitumen. Because of its compatibility to bitumen adhesion, stripping is considerably resisted.
The Simple Pile Load Test (SPLT)
Authors: Lee MW , Paik SW , Lee WJ , Yi CT , Kim DY , Yoon SJ
Published: February 2009

For the design of pile foundations, estimation of the pile-bearing capacity is important because the size and number of piles are determined from the estimation. Although there have been many different methods predicting pile-bearing capacity, no one method provides reliable predictions except for methods based on actual loading tests. Due to time and money constraints, conventional pile-load tests tend to be limited and, consequently, design relies on relatively high factors of safety. In this paper, a new and simple method of performing pile-load tests is introduced. The suggested method uses a separable pile shoe with a reduced-size sliding core and has proved to be efficient in terms of both time and cost. By choosing the newly developed testing method, a more economical pile design can be attained.
Indirect Tension Tests on Rock—Analytical/Numerical Correction for Material Bimodularity
Authors: Chen R , Stimpson B
Published: February 2009

Many rocks have different deformational properties when loaded in tension and in compression. This property is referred to as bimodularity. The influence of bimodularity on four of the most commonly utilized indirect tension testing methods for measuring the tensile strength of rock is investigated analytically and numerically in this paper. These indirect tension methods include the three-point beam-bending test, the hydraulic extension test, the Brazilian test, and the ring test. It is shown that tensile strengths for rock derived from these tests are overestimated if the normal assumption of equal moduli in tension and compression is made. The actual tensile strength may be determined if the moduli ratio in tension and compression is known.
Ultimate Bearing Capacity of Rectangular Foundations on Geogrid-Reinforced Sand
Authors: Omar MT , Das BM , Yen S-C , Puri VK , Cook EE
Published: February 2009

Model test results for the ultimate bearing capacity of rectangular surface foundations supported by geogrid-reinforced sand are presented. The tests were conducted using one type of sand at one relative density of compaction with only one type of geogrid. The length-to-width ratios of the model foundations were varied as 1, 2, 3, and ∞. Based on the model test results, the maximum required depths of reinforcement and the sizes of the geogrid layers to obtain maximum-bearing-capacity ratios have been presented.
Large-Scale Triaxial Compression Testing of Geocell-Reinforced Granular Soils
Authors: Bathurst RJ , Karpurapu R
Published: February 2009

The paper describes the results of a series of large-scale triaxial tests carried out on 200-mm-high isolated geocell-soil composite specimens and unreinforced soil specimens. Two different aggregate soils were used in the test program. The reinforced specimens were tested with a height-to-diameter ratio of unity, which matches the dimensions of these systems in a typical base reinforcement application. The results illustrate the stiffening effect and strength increase imparted to the soil by the enhanced confinement effect. Comparison of reinforced and unreinforced soil specimens shows that the frictional resistance described by the peak friction angle of the soil infill is applicable to the composite structure as well. A simple elastic membrane model can be used to estimate the additional apparent cohesion present in the composite structure.
Estimating Water Content of Soils from Electrical Resistivity
Authors: Kalinski RJ , Kelly WE
Published: February 2009

Electrical resistivity has been demonstrated to be an effective predictor of various soil hydraulic properties including water content, degree of saturation, and hydraulic conductivity. Standardized laboratory procedures for measuring soil electrical resistivity are based on the use of the Miller soil box for determining soil corrosive potential from soil resistivity. However, these procedures and the Miller soil box do not allow for the flexibility in measurements necessary to develop explicit relationships between soil resistivity and hydraulic properties. As an alternative to the use of the Miller soil box, circular four-probe resistivity cells provide a measurement method that can be used to develop explicit relationships between soil resistivity and hydraulic parameters. For a test experiment, relationships were developed where volumetric water content could be estimated from soil resistivity with a standard error of 0.009.
Some Experiments on Restrained Shrinkage of Clays Undergoing Drying
Authors: Sibley JW , Williams DJ
Published: February 2009

This paper describes engineering applications which show the engineering significance of testing the phase composition of soils, including determining the level of water saturation. It further explains why, in order to accurately model in situ conditions in soil deposits, it is necessary to test the phase composition of soil under conditions of horizontal restraint and changing moisture content. The paper reviews the lineal measurement method of Sibley and Williams (1989), which was initially developed to test unrestrained clays. The method has now been adapted for use in characterizing phase relationships in horizontally restrained soil specimens undergoing drying. Results obtained using the new test have drawn attention to the fact that while soils undergoing drying are invariably restrained by naturally occurring mechanisms, the level of this restraint may vary widely. A useful index of the level of restraint applied to a slurried soil specimen undergoing drying is the moisture content at which initially 1-D (vertical) shrinkage behavior becomes isotropic.
Shear Strength of Very Soft Clay-Sand Mixtures
Authors: Tan T-S , Goh T-C , Karunaratne GP , Lee S-L
Published: February 2009

To treat a deposit of clay slurry in situ, sand is often added with the aim of trapping the sand in the upper portion of the slurry. The presence of the trapped sand may directly improve the shear strength of the slurry or contribute indirectly to the improvement by accelerating the consolidation. For this treatment to be effective, an important consideration is the improvement in the shear strength of the slurry as sand is added. A laboratory study of this is reported here. To rapidly determine the shear strength of the mixture, the fall cone method and a penetration test that was developed to measure very low shear strength were used. For the clay slurries studied, the added sand grains seemed to “float” in the clay without increasing the shear strength if they were sufficiently far apart. Treating the clay slurry as a fluid filling the “voids” in the sand, the void ratio of the sand for which a marked increase in shear strength is observed is about 5. The liquid limit of the mixture is also found to follow approximately a linear mixture law unless the amount of sand added is enough to ensure that the void ratio of the sand is less than 5, which is in agreement with the earlier result.
An Approximate Method for Estimating the Consolidation Behavior of Soft Sensitive Clays
Authors: Joshi RC , Achari G , Griffiths FJ
Published: February 2009

An approximate, semi-theoretical method to determine the complete consolidation curve of undisturbed sensitive soils from index properties and in situ undrained shear strength is presented. The consolidation curve for the soft sensitive soils consists of three distinct zones. In order of increasing stress, these zones are described as cemented, transitional, and uncemented zones. A relationship between undrained strength and preconsolidation stress of such soils is employed in the prediction of the stress level at which the cemented zone terminates. The slope of the stress path for the loading of sensitive soils during the transition phase of consolidation is less than the slope during the cemented phase. Further, assuming that the stress path in the transitional phase is a straight line at a constant angle to the p′ axis, a relationship between the end of the cemented and the end of the transitional zones of behavior can be derived. Since sensitive soils in the uncemented zone behave similarly to normally consolidated soils, the entire consolidation curve can be approximated.
An Image Analysis Method for Studying Movements in Granular and Solid Bodies
Authors: Gustafsson L , Knutsson S
Published: February 2009

A method based on image analysis of video recordings is presented for studying and measuring movements in granular materials. The method is easy to use, does not require any tracers, and makes extensive experiments feasible. Calibration tests show good repeatability. Measurements are presented of movements in a sand mass into which a piston is driven. The method is also useful for studying the deformation of solid bodies. The deformation of undrained clay specimens subjected to uniaxial forces is demonstrated using the proposed method.
Centrifuge Modeling of Laterally Loaded Pile Groups in Sands
Authors: McVay M , Bloomquist D , Vanderlinde D , Clausen J
Published: February 2009

Presented is a novel apparatus to drive and laterally load groups of six to nine piles in flight. The main component of the device is a flat plate with multiple apertures which are opened or closed through pneumatic solenoids while being raised or lowered with stepping motors via a PC. Presently, both lateral load versus deformation and load distribution within the rows can be measured.

Testing on both loose and medium dense sands at three and five-pile-diameter spacings have been completed for free-headed groups of nine piles. It was found that as the soil's density increased, so did the group's lateral resistance as well as the variation from row to row. The five-pile-diameter groups carried larger lateral loads and resulted in a more even load distribution from row to row than its three-diameter counterpart. Work is underway to test larger groups as well as inclined piles.
Laboratory Investigation on Bitumen Coating and Polyethylene Sheeting for Downdrag Reduction in Piles: A Comparative Study
Authors: Tawfiq KS
Published: February 2009

In this study, the polyethylene sheeting method for downdrag mitigation in piles has been investigated along with the conventional bitumen coating method. A large number of concrete blocks were prepared with different arrangements of bitumens and polyethylene sheets and tested in the laboratory using direct shear apparatus. The shear resistance of the concrete-bitumen-soil specimens was susceptible to changes in temperature, strain rate, and normal stresses. Bitumen-coated specimens tested with crushed limestone exhibited the highest friction. Soil particle penetration into bitumen doubled the shear resistance of the bitumen coating. Factors that govern the shear behavior of bitumen coating were found to slightly affect the friction characteristics of the concrete-polyethylenesoil specimens. According to the laboratory results, furnishing the concrete blocks with two 6-mil (0.15-mm) polyethylene layers reduced the shear resistance by 78%. More reduction could be achieved from the two oil-lubricated polyethylene sheets. This layering arrangement provided the most effective performance (95% efficiency) for the polyethylene sheeting method.
Impact-Echo Response of Hollow Cylindrical Concrete Structures Surrounded by Soil and Rock: Part I—Numerical Studies
Authors: Lin J-M , Sansalone M
Published: February 2009

The studies summarized in this paper and the following paper in this issue demonstrate that the impact-echo method can be used for integrity testing of concrete pipes, mine shaft liners, and tunnel liners in contact with soil or rock. Results obtained from numerical (finite element) studies are presented in this paper (Part I), and results obtained from experimental studies on mine shaft liners are presented in the following paper (Part II). These results show that the impact-echo response depends upon the acoustic properties of the surrounding material, as well as on the acoustic properties, geometry, and condition of the concrete structure. It is shown that cracks and voids in the concrete structure can be detected independent of the surrounding material. If the concrete structure is solid, the thickness of the concrete can be determined, except when the acoustic properties of the rock and concrete are similar and the concrete is in contact with the rock. The presence of delaminations or voids (air- or water-filled) at the concrete/rock interface can be identified when the acoustic impedance of the rock is similar or larger than that of the concrete.
A New Combined Servo-Controlled Loading Frame/Direct-Shear Apparatus for the Study of Concrete or Rock Joint Behavior Under Different Boundary and Loading Conditions
Authors: Mouchaorab KS , Benmokrane B
Published: February 2009

A new combined servo-controlled loading frame/direct-shear apparatus has recently been developed at the Civil Engineering Department of Université de Sherbrooke. This direct-shear device is capable of shear testing of rock joints under constant normal stiffness or constant normal load boundary conditions. Due to its combination with a servo-controlled loading frame, it allows load as well as strain and stroke control, including static and cyclic paths. This paper describes this direct-shear apparatus and illustrates results of static and cyclic shear tests undertaken on circular-section rock specimens with irregular interface geometry and on regular-shaped interface specimens made from cement-based mortar.
A General Dynamic Model for the Resonant Column/Quasi-Static Torsional Shear Apparatus
Authors: Ashmawy AK , Drnevich VP
Published: February 2009

A new model is proposed that allows for more general boundary conditions at both the active and passive ends of resonant column apparatus, especially those incorporated within the resonant column/quasi-static torsional shear devices. The improved three-degree-of-freedom model can be used in order to obtain more accurate measurements of the dynamic properties of tested soils when the base and the reaction mass of the apparatus are not perfectly fixed. This becomes particularly important in the hybrid resonant column/quasistatic torsional shear apparatus where the load cell located below the bottom platen provides additional flexibility to the passive end and the inertia of the reaction mass of the Hardin-type oscillator is relatively small. The analysis confirmed that use of the model is particularly important if the natural frequency of the soil-apparatus system is close to that of the passive end or reaction system, and that the calculated modulus and damping values can be highly inaccurate if simplified boundary conditions are assumed. Such situations especially occur when very soft soils, very stiff soils, or rock specimens are tested. The solution was programmed in a spreadsheet where both the shear modulus (G) and the damping ratio (D) are established for a given set of measurements and apparatus constants. In order to obtain the necessary apparatus constants, calibration procedures are presented for a resonant column/quasi-static apparatus. Comparison of existing models and the new solution to the observed response for a rubber testing specimen showed that the three-degree-of-freedom assumption is more accurate in modelling the apparatus boundary conditions.
Compaction Control of Earth-Rock Mixtures: A New Approach
Authors: Torrey VH , Donaghe RT
Published: February 2009

A new method for compaction control of earth-rock mixtures has been developed which permits the calculation of the maximum dry unit weight and optimum water content of the total material from corresponding values obtained on either the minus 3/4-in. (19.1-mm) or the minus No. 4(4.76-mm) fraction. The new concepts are substantiated by showing their applicability to a wide range of gradations of earth-rock mixtures tested by the U.S. Army Engineer Waterways Experiment Station and other previous investigators. Calculations of maximum dry unit weight and optimum water content of the total material from corresponding values for a fraction are made using a density interference coefficient and optimum water content factor which are shown to be linearly related to gravel content in the material in log-log coordinates. It is also shown that if a sufficient range in gravel content exists in the minus 3/4-in. (19.1-mm) fractions of the total materials, the log-log linear relationships among density interference coefficient, optimum water content factor, and gravel content can usually be obtained without large-scale compaction testing of the parent total materials. In essence, the new method provides project-specific “rock corrections” which accurately track the compaction parameters of the entire family of generically related total materials throughout the range in their gravel contents and maximum particle sizes.
Techniques for Assessing the Nonlinear Resilient Response of Unbound Granular-Layered Structures
Authors: Dastich I , Dawson A
Published: February 2009

The resilient stress-deformation characteristics of aggregates that form granular pavement layers are reviewed. A standardized plate bearing test (PBT) is proposed that separates resilient and permanent deformation readings and detects material stress dependency. A nonlinear, stress-dependent model proposed by Ehrler is used to reproduce the observed deformation behavior of a granular layer subjected to repeated plate bearing tests at different applied stress levels. The use of equipment exploiting the relationship between resilient behavior and the natural frequency of vibration of a mass resting on a semi-infinite half space (the natural vibration method—NVM) is described. The results predict granular pavement stiffnesses when a nonlinear, stress-dependent model is employed, and these are very simply related to PBT results obtained on the same material. The NVM approach may be more practical than the modified PBT procedure proposed as it can be used more quickly.
Consolidation Behavior of Soils
Authors: Sridharan A , Prakash K , Asha SR
Published: February 2009

Based on Terzaghi's consolidation theory, percent of consolidation, U, versus the time factor, T, relationship for constant/linear excess pore water pressure distribution, it is possible to generate theoretical log10(H2/t) versus U curves where H is the length of the drainage path of a consolidating layer, and t is the time for different known values of the coefficient of consolidation, cν. A method has been developed wherein both the theoretical and experimental behavior of soils during consolidation can be simultaneously compared and studied on the same plot. The experimental log10(H2/t) versus U curves have been compared with the theoretical curves. The deviations of the experimental behavior from the theory are explained in terms of initial compression and secondary compression. Analysis of results indicates that the secondary compression essentially starts from about 60% consolidation. A simple procedure is presented for calculating the value of cv from the δ-t data using log10(H2/t) versus U plot.
Improvements to a Stress-Path Triaxial Cell
Authors: Aversa S , Vinale F
Published: February 2009

Stress-path triaxial cells are presently used all over the world. Accurate use of this type of apparatus allows an investigation into the mechanical behavior of soils with regard to a wide range of stress and strain. A correct evaluation of small-strain stiffness requires an accurate definition of the compliance curve of the apparatus and the possibility of performing tests in stress-controlled conditions. However, in the standard stress-path cell, compliance curves are often nonlinear and nonrepeatable. Moreover, in most standard stress-path apparatus, the pressure supply is limited to 1000 kPa, which makes it impossible to carry out stress-controlled tests at high confining pressures. The observation of these limitations prompted adjustments in the design of the cell, described in the present paper. With the revised design, it is possible to apply a deviatoric stress up to 1500 kPa under stress-controlled conditions with a cell pressure of 1000 kPa using a 1000-kPa pressure supply. The stiffness of the cell was also significantly increased, up to ten times the stiffness of the original design.
Granulometric Evaluation of Particle Size Using Suspension Pressure During Sedimentation
Authors: Zhang Z , Tumay MT
Published: February 2009

A new method, computerized granulometric analysis in suspension (C-GRAINS), is suggested for the sedimentation analysis of soil particles based on the relation between the specific weight and liquid pressure of a soil suspension. Theoretical aspects concerning this new testing method are discussed, and a prototype C-GRAINS system is fabricated accordingly. The general behavior of the new system is studied, and the corresponding sedimentation results are compared to current ASTM standards.
Liquid and Plastic Limits as Determined from the Fall Cone and the Casagrande Methods
Authors: Wasti Y
Published: February 2009

The shortcomings of the conventional methods of determining the liquid limit using the Casagrande apparatus and the plastic limit by rolling soil balls by hand have led to the investigation of the fall cone (cone penetrometer) as an alternative. The use of the fall cone test to determine the liquid limit has long been adopted by several countries, but the proposal to use this test to determine the plastic limit as well, redefined on the basis of a strength criterion, is rather recent. In this paper the liquid and the plastic limits as determined by these two procedures for a number of natural soils and artificial soil mixtures are presented. A comparative and critical survey of experimental results involving the use of various cones to obtain consistency limits is also included.
Geotechnical Properties of Expanded Shale Lightweight Aggregate
Authors: Valsangkar AJ , Holm TA
Published: February 2009

In recent years lightweight aggregates are being used increasingly in geotechnical applications. This paper presents results of large-size one-dimensional compression and direct shear tests performed on lightweight aggregate. The compressibility and shear strength characteristics of the lightweight aggregate are compared with those of normal-weight aggregate using the same experimental setup. Results of the direct shear tests performed to determine the angle of friction between the geotextile and lightweight aggregate are also presented. In addition, static shear modulus values as determined from model pile tests are presented and compared with those reported for normal weight aggregates.
Design of a Large Calibration Chamber
Authors: Sweeney BP , Clough GW
Published: February 2009

The design and operation of a conceptually simple, low-cost chamber for calibration of cone penetrometers and other in situ devices is described. The chamber weighs over 5500 kg and houses a 4400-kg soil sample that is 1.5 m in diameter and height. Operations in the chamber are automated using a self-equilibrating hydraulic insertion frame, a soil pluviation system for sand placement, a vacuum unit for removing sand, and an automatic data acquisition system. The results from a series of cone penetration tests in Monterey No. 0/30 sand, using standard and miniature cones, are also discussed. These tests indicate that the chamber design was successful and also that nearly homogeneous samples could be prepared at different relative densities using interchangeable rainer plates.
Shear Zone Characterization in Sands by Carbowax Impregnation
Authors: Hryciw RD , Irsyam M
Published: February 2009

A procedure is presented for determining the void ratio distribution of very small zones in soil by carbowax impregnation. If the wax is injected slowly, complete filling of voids occurs and volume measurements become unnecessary. Thus, even irregularly shaped volumes can easily be characterized. The technique was employed in determining the void ratio distribution in the intrarib region of a ribbed inclusion in sand during direct cyclic shearing. The measured void radios supported magnified video observations.
Evaluation of Allowable Pressure Under Foundations
Authors: Reznik YM
Published: February 2009

To understand the surcharge effect on test-loading results, water-saturated loessial soils were tested by bearing plates of different sizes in open pits and boring holes. All pit bottoms were accurately prepared for experiments. The surcharge around the bearing plate with an area of 600 cm2 was simulated by special equipment. Results of field experiments showed that the proportionality limit for water-saturated loessial soils tested without surcharge was at least 25% less than obtained with the surcharge.
Automated Triaxial Testing of Soft Clays: An Upgraded Commercial System
Authors: Sheahan TC , Germaine JT , Ladd CC
Published: February 2009

The paper evaluates the ability of a widely used automated commercial testing system to perform Ko consolidated-undrained triaxial compression and extension (CKoUC/E) tests on normally consolidated clay. The commercial system uses control software on a microcomputer to operate three digital pressure-volume controllers that control and measure the pore water pressure and volume, the radial stress, and the axial stress and strain for a specimen within a Bishop and Wesley Hydraulic Triaxial Apparatus. Because the commercial system calculates axial stress and strain by relying on indirect measurements assuming idealized behavior of the axial loading assembly, the system was modified to directly measure axial stress and strain. The system was also enhanced to enable shear in triaxial extension and to improve certain other testing procedures. Comparison of results from CKoUC/E tests obtained by the resulting reference system with prior data on resedimented Boston Blue Clay shows good to excellent agreement in 1-D compressibility and undrained stress-strain-strength characteristics. In contrast, stresses recorded by the commercial system resulted in significant overestimates of preconsolidation pressure, undrained strength, and the effective stress envelope, primarily caused by unquantifiable behavior of the axial loading assembly. Based on these results and other experience, the paper suggests features warranting special attention when selecting a commercially available automated triaxial system in order to upgrade the experimental capabilities of a laboratory.
Effect of Backfill Thrust on Vertical Pressure Distribution in Reinforced Soil Model Walls
Authors: Ashaari Y , Arenicz RM
Published: February 2009

The magnitude and distribution of vertical stress are required for the design of reinforced soil wall. A laboratory investigation utilizing a physical model of reinforced soil wall was performed to determine the effect of backfill thrust on the vertical pressure distribution within the reinforced zone. Results obtained were compared with those predicted by the theoretical vertical pressure distribution (uniform, trapezoid, and Meyerhof's).

The model wall behavior, particularly the distribution of vertical stress within the reinforced zone of the structure, was investigated in four series of tests with different boundary conditions and construction procedures. The results obtained were, as expected, different from either of the three theoretical pressure distributions. It was found that thrust of backfill material placed at the back of reinforced zone reduces the vertical pressure near the end of reinforcement strips while increasing it in the remaining part of the reinforced zone. The reduction of pressure near the strip ends conforms to the trapezoid theory. However, the maximum increase in pressure does not occur at the facing as predicted by the theory.
Field Hydraulic Conductivity Tests for Compacted Soil Liners
Authors: Sai JO , Anderson DC
Published: February 2009

Field hydraulic conductivity tests are required to determine the in situ hydraulic conductivity of compacted clay soils used in the liners for hazardous waste management facilities. The test must be capable of measuring hydraulic conductivities of 1 × 10−9 m/s or less, and the values obtained must be representative of the overall soil liner. Few of the methods available are capable of both measuring low hydraulic conductivities and obtaining representative values. Test methods which meet these requirements include large single-ring infiltrometers, sealed double-ring infiltrometers, and collection lysimeters. The main drawback in the use of collection lysimeters is that it can take months to obtain steady-state hydraulic conductivity values. Sealed double-ring infiltrometers are practical to use and have the advantage of few ambiguities in the experimental procedures, few possibilities for yielding false low values, and are large enough to yield results representing the overall liner characteristics.

Infiltrometers used on compacted soil liners should cover at least one elementary volume (REV) (e.g., at least 2 m2), and, in addition, at least three separate tests should be conducted to characterize spatial variability of the field hydraulic conductivity.
A Biaxial Apparatus for Testing Soils
Authors: Drescher A , Vardoulakis I , Han C
Published: February 2009

A biaxial compression apparatus for investigating shear-band formation and growth in dry and water-saturated sand and clay specimens is described. This apparatus is a modification of the device designed by Vardoulakis and Goldscheider [1] for testing planar shear banding in sands. The modifications involve improved axial load guidance, low friction linear bearing, and enhanced load and displacement measurement instrumentation. The apparatus allows for accurate prelocalization material behavior and shear-band growth investigation. Specimen preparation and data evaluation procedures are described, and test results on dry Ottawa sand are presented.
Design and Testing of a Synthetic Clay Soil
Authors: Lewis MJ , Blaney GW
Published: February 2009

A synthetic clay soil mixture was designed and fabricated to comply with similitude requirements set forth in a dynamic scale-model pile group foundation test. The prototype soil was a stiff, fissured, overconsolidated clay soil at the University of Houston Pile Test Facility. The dynamic response of the model soil was determined through testing by resonant column/torsional simple shear methods and by seismic wave velocity tests in the model test bed. The synthetic clay soil was more nearly linear elastic to higher strain levels with less damping than natural clays. The ability of the soil to regain its strength after disturbance was beneficial to the scale-model tests. The design, fabrication, and testing procedures utilized to obtain an appropriate geotechnical material for scale-model soil/structure interaction tests is detailed in this article.
Abrasion Tests for Railroad Ballast
Authors: Selig ET , Boucher DL
Published: February 2009

Mechanical abrasion tests are an important basis for evaluating the suitability of rock for use as railroad ballast. This paper considers three such tests: Los Angeles abrasion, the test primarily used by North American railroads; Deval abrasion, the test primarily used by British Rail; and mill abrasion, a relatively new test being proposed for use in North America. The mill abrasion test is similar to the Deval test. Previous evaluations of the Deval and mill abrasion tests are summarized. Then test data generated by the authors are presented to show the effect of factors influencing the mill abrasion test results. Finally, mill and Los Angeles abrasion results obtained on a wide range of rock type are compared and evaluated using petrographic analysis.

Ranking of rock type by the mill test is different than by the Los Angeles test. The products of abrasion are quite different, too—the mill test primarily produces particles smaller than the No. 200 sieve, while the Los Angeles test primarily produces particles larger than the No. 200 sieve. Thus these two tests appear to be influenced by different rock structural characteristics. In the mill and Deval tests, the amount of abrasion increases with increasing particle size. Also, the amount of abrasion is significantly greater for freshly crushed particles than for worn particles. In the mill test the abrasion is significantly greater when the test is conducted wet than when conducted dry. The petrographic analysis was useful in explaining the differences in results for the various rock type.
Design, Construction, and Testing of a Large-Scale, Radial Fracture Flow Model
Authors: Atkinson LC , Gale JE
Published: February 2009

Materials and procedures used in previous laboratory studies of flow in fractures were reviewed. Based on this review, a 3-m-high by 1.5-m-diameter cylindrical radial flow model with a single horizontal fracture was designed and constructed out of concrete. The fracture was created by placing a sheet of geotextile between the top and bottom halves of the cylinder during pouring of the concrete. Twenty-eight piezometers were cast in-place in the fracture plane, and displacement transformers were installed both on the circumference of the cylinder and in the wellbore to measure fracture deformation. The model also incorporated features designed to allow withdrawal and injection tests to be conducted with different flow boundary conditions, applied loads, and wellbore diameters. This laboratory setup was used to investigate flow and deformation in the immediate vicinity of a vertical well intersecting a single rough, deformable, horizontal fracture at flow rates of practical interest to the geotechnical and petroleum industries.
Corrections for Membrane Strength in the Triaxial Test
Authors: Kuerbis RH , Vaid YP
Published: February 2009

Equations based on elastic thin cylindrical shell compression theory are developed for correcting stresses for membrane strength in a triaxial test. The corrections are expressed in terms of the unstretched dimensions, the diameter and thickness of the membrane, the axial and volumetric strain of the cylindrical membrane cavity referenced to its unstretched dimensions, together with E and v of the membrane rubber. The development specifically considers changes in membrane thickness as they occur during the straining process, and in particular its influence on the specification of E of the membrane. Direct experimental verification of the derived stress correction is provided in support of their validity.
Classification of Expansive Soils by Sediment Volume Method
Authors: Sridharan A , Rao SM , Joshi S
Published: February 2009

A soil expansivity classification is proposed based on the sediment volume ratio defined as the ratio of the sediment volume in 0.025% sodium chloride solution to that in kerosene. The results of the proposed classification agree well with one based on the oedometer test results of compacted soil specimens.