bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of Silty Sand Specimens for Large- and Small-Scale Tests
Authors: Brandon TL , Clough GW , Rahardjo PP
Published: February 2009

In the course of research concerning the relation of cone penetration results and liquefaction resistance, it was necessary to develop a reliable method for preparation of silty sand specimens for laboratory triaxial testing (3.6 by 7.1 cm in diameter) and for a large-scale calibration chamber (1.5 by 1.5 m in diameter). The objective was to simulate the in situ soil fabric and to allow for creation of a range of densities. Four alternate procedures were studied, including kneading compaction, pluviation through air, pluviation through vacuum, and consolidation from a slurry. The primary conclusions from the research were:

1. Kneading compaction is effective in producing laboratory specimens with a range of densities, but it is not an effective procedure for placing these materials in the large-scale calibration chamber.

2. Pluviation through air and vacuum creates specimens with unrealistically high void ratios. Obtaining a range of densities was not possible.

3. Slurry consolidation proved to be successful in creating specimens with a range of densities and was the technique chosen for the calibration chamber.

Only vertical drainage was used in the calibration chamber to avoid formation of a specimen with a soft core surrounded by stiff sides. Eighteen to twenty days were required for consolidation, and the density of the specimens along a vertical profile varied by no more than 6% from the average density. There was little evidence of segregation of fines.
Calibration of a Dynamic Penetrometer for Compaction Quality Control of Boiler Slag
Authors: Acar YB , Puppala AJ , Seals RK
Published: February 2009

A dynamic penetrometer was designed for the purpose of evaluating compaction quality in fills constructed with boiler slag. Laboratory and field calibration tests were conducted to study the effect of densification on dynamic penetration resistance. The effects of specimen preparation method (pluviation and impact compaction) and saturation on dynamic penetration resistance were investigated in the laboratory. A 0.91-m (3-ft)-deep test fill with dimensions of 6.1 m (20 ft) by 30.5 m (100 ft) was prepared in the field. Dynamic penetration resistance and in situ densities were recorded in this slag fill after 0, 2, 4, 6, 10, and 16 passes of a smooth drum vibratory roller of 5.6 tons (11.2 kips). The field-resistance values were compared with laboratory values. Charts are provided to aid both in selecting the lift thickness/number of roller passes and also for field assessment of densification in boiler slag using the dynamic penetrometer.
Expansive Soils under Cyclic Drying and Wetting
Authors: Dif AE , Bluemel WF
Published: February 2009

An approach was developed to study the swell-shrinkage behavior of expansive soil samples in the laboratory under the action of the actual load to which the soil will be subjected in the field. The fatigue phenomenon due to cyclic drying and wetting has been under investigation, and this paper describes in detail the modified oedometer used in this investigation and the testing procedure adopted. Some typical test results are used to illustrate the fatigue behavior of undisturbed expansive soil specimens during cyclic drying and wetting.
Piezo Film Technology and Applications in Geotechnical Testing
Authors: Santamarina JC , Wakim TN , Tallin AG , Rab F , Wong J
Published: February 2009

Piezo films are thin, piezoelectric membranes that can be used both as source or as receiver. They may be adapted to a variety of in situ and laboratory geotechnical testing needs. This paper summarizes fundamental concepts in piezo film technology and the physical properties of this material. The principles behind common utilizations are reviewed, and three geotechnical applications are described: a low-cost field sensor and modified triaxial and oedometer cells to measure low-strain moduli in resonant and pulse mode.
Sled for In Situ Penetration Testing
Authors: Atwood MJ , Benoit J
Published: February 2009

In situ testing devices such as the dilatometer, the piezocone, the pressuremeter, and the field vane generally require the use of a drill rig for penetration through soils. This paper describes a multipurpose portable pushing frame built at the University of New Hampshire and designed to be used with most in situ testing probes. This rig is compact, inexpensive, easy to use, and can operate on sites usually not accessible to conventional drilling rigs.
Characteristics of a Bentonite Slurry as a Sealant
Authors: Edil TB , Muhanna ASH
Published: February 2009

Many of the technologies that relate to groundwater use bentonite slurries. The results of a laboratory investigation aimed at determining the characteristics of a bentonite slurry as a sealant are presented herein. Slurry indicator tests were used to determine the physical characteristics of the slurry, and performance tests, such as hydraulic conductivity and model tests, were conducted to evaluate the behavior of the slurry as a sealant. The results indicate that the final success of a bentonite sealant depends on its structural stability and the characteristics of the filter cake it generates. A bentonite slurry with some formation cuttings such as sand provides a sealant superior to a pure slurry. Sealing behavior of a slurry is related to its bentonite content; however, this relationship is not one of monotonical increase and there is an optimum bentonite content. The variety of indicator tests used were useful; however, filtration properties appear to be the most appropriate indicator of sealing behavior.
Blast-Induced Liquefaction of an Alluvial Sand Deposit
Authors: Charlie WA , Jacobs PJ , Doehring DO
Published: February 2009

A series of six different explosive charges ranging from 0.0045 to 9.06 kg were detonated at a depth of 3 m below a sand island in the South Platte River, northeast Colorado. Pore pressure, particle velocity, and residual pore pressure were measured at several locations. Liquefaction was induced in the dense, saturated, coarse sand at a depth of 3.0 m when peak compressive strain exceeded 0.01%, peak particle velocity exceeded 0.16 m/s, or at scaled distances less than 3 m/kg⅓. No residual pore pressure was induced at a peak compressive strain less than 0.002% at peak particle velocity less than 0.03 m/s, or at scaled distances greater than 16 m/k⅓.
Pullout Resistance of Steel Geogrids with Weathered Clay as Backfill Material
Authors: Bergado DT , Hardiyatimo HC , Cisneros CB , Chun CJ , Alfaro MC , Balasubramaniam AS , Anderson LR
Published: February 2009

The pullout resistance of welded steel geogrid reinforcement embedded in poor-quality, cohesive-frictional backfill material such as weathered clay was investigated. Laboratory pullout tests were conducted on various reinforcement sizes, mesh geometry, and compaction conditions of the backfill material. Field pullout tests were also conducted to investigate the pullout resistance of reinforcements embedded at representative overburden, field moisture, and density conditions. The soil-reinforcement interaction indicated the dominant role of passive or bearing resistance contributed by the transverse members to the total pullout resistance. The frictional resistance of the longitudinal members was found to contribute only about 5 to 15% of the total pullout resistance. It was observed that the reinforcement moved nearly as a rigid body and that the pullout resistance along the reinforcement is uniformly mobilized. The field pullout test provided higher pullout resistance compared to that of the laboratory test. Comparison of the predicted pullout bearing resistance with the observed data indicated that the prediction based on the bearing failure model formed the upper boundary while the prediction associated with the punching failure model provided the lower boundary. An empirical equation was proposed to predict the bearing resistance of the transverse members with reasonable accuracy.
Introduction to C. A. Hogentogler Award Article by David I. Stannard
Authors: Knodel P
Published: February 2009

The 1991 C. A. Hogentogler Award was presented to David I. Stannard of the United States Geological Survey in Denver, Colorado. The Hogentogler Award is presented to the author or authors of a paper of outstanding merit on soil or rock for engineering purposes published by the Society. The award was established in 1953 to stimulate research, encourage the exchange of knowledge, and recognize meritorious effort. It is administered by a three-member Award Committee of Committee D-18 on Soil and Rock.
“1γ2ɛ”: A New Shear Apparatus to Study the Behavior of Granular Materials
Authors: Joer H , Lanier J , Desrues J , Flavigny E
Published: February 2009

In this paper, we present a new kinematic shearing apparatus named “1γ2ɛ,” which has been developed at the Institut de Mécanique de Grenoble (IMG) with the financial support of the GRECO Géomatériaux. Thanks to its kinematic control, a specimen may be subjected to conditions found in general plane strain. Our aim is to study the rheology of granular material in situations with rotation of strain or stress principal axes.

Following the initial description of our technical choices for the design of this new apparatus, we present results concerning isotropic tests and tests at constant volume with and without rotation of principal axes. It should be noted that the cyclic effect of rotation of principal axes may induce liquefaction.
Effect of Reinforcement Layout on Soil Strength
Authors: Arenicz RM
Published: February 2009

This paper presents the results of a laboratory investigation of the shear strength of soil reinforced with metal strips. The investigations were conducted using a large, specific purpose-built shear box. The effects of reinforcement layout, as well as type of strips and quantity of reinforcement, on soil shear strength at failure were tested. The investigations involved three reinforcement layouts (along the shear surface, across the shear surface, and spread evenly in both directions), two types of strips (smooth, ribbed), and three quantities of reinforcement (strips of different widths). The results indicate the importance of reinforcement layout in soil shear strength enhancement, with strips spaced equally in both directions found to be most effective. Other practical conclusions regarding the effects of type and width of strips on soil strength improvement were also presented.
The Influence of Test Procedure on Correlation of Atterberg Limits with Liquefaction in Fine-Grained Soils
Authors: Koester JP
Published: February 2009

Liquefaction potential of fine-grained soil deposits is today judged, in part, based on an observed correlation of Atterberg limits to field performance of soils shaken by the 1976 Tangshan earthquake in the People's Republic of China (PRC). Criteria were subsequently developed and adopted into current liquefaction potential evaluation practice without regard to the test procedures used to measure liquid and plastic limits in the PRC. Liquid and plastic limits tests are, in fact, performed in the PRC using a special laboratory fall cone penetrometer apparatus. An experimental study was made to compare Atterberg limits determined for low plasticity artificial soil mixtures and a limited number of split spoon samples using U.S. and PRC standard procedures. Study results, corroborated by earlier published comparisons of Casagrande-type percussion tests and various fall cone devices, indicate that liquid limits produced by the Casagrande test consistently exceed those produced using the PRC fall cone by about 4% (water content). The lineal extent of foundation soils at Sardis Dam, Mississippi judged to require remedial action against liquefaction varied significantly with fines content, liquid limit, and natural water content; the impact of this study on preliminary estimates of the extent of the dam requiring remedial action is briefly discussed.
Use of Air Bag System for Instrumentation of Lateral Load Tests on Previously Installed Pipe Piles
Authors: Kramer SL
Published: February 2009

A simple and inexpensive air bag system for allowing measurement of the deflected shape of laterally loaded piles has been developed. The air bag system may be used for hollow piles that have already been installed. The system includes an inclinometer casing that is held against the inner wall of the pile by an inflated air bag. Tests on small- and large-diameter steel pipe piles at two different locations showed that the air bag system performed reliably. The air bag system can allow measurement of p-y characteristics in lateral load tests on piles for which the possibility of such measurement may not have previously existed.
An Alternate Method for Determining the Klinkenberg Correction
Authors: Stormont JC , Daemen JJK
Published: February 2009

Gas slip phenomena in low-permeability media are typically accounted for by means of the conventional Klinkenberg correction. This correction is derived from gas permeability tests conducted under different pore pressures. An alternative method for obtaining the Klinkenberg correction is given which uses the results from gas permeability tests conducted with different gases under the same pore pressure. Both methods have been applied to a series of gas permeability measurements on rock salt. Changes in the pore structure during permeability testing precludes use of the conventional Klinkenberg method. The alternative method is successful when permeabilities are measured with steady-state techniques.
An Experimental Method for Determining Membrane Penetration
Authors: Choi JW , Ishibashi I
Published: February 2009

A new and simple experimental method is proposed for the determination of membrane penetration due to changes of the effective confining pressure in triaxial and hollow cylinder tests. The proposed method has advantages over existing methods in that it requires neither special devices nor questionable assumptions. It only requires a series of drained isotropic compression tests in a conventional triaxial device with plastic liners. The results from the proposed method are compared to those from several existing experimental and analytical methods.
A New Traveling Sand Pluviator to Reconstitute Specimens of Well-Graded Silty Sands
Authors: Lo Presti DCF , Berardi R , Pedroni S , Crippa V
Published: February 2009

A new traveling sand pluviator to reconstitute small specimens for laboratory tests was developed in joint research between the Research Center of the Italian National Electricity Board (ENEL CRIS) of Milano and the Department of Structural Engineering of the Politecnico di Torino.

The pluviator proved satisfactory in reconstituting small-size specimens because it provided a very high degree of spatial uniformity of density and grain-size distribution.

Furthermore, it was shown that a traveling pluviator is preferable to a stationary one even in reconstituting large-size specimens to achieve a higher degree of spatial uniformity.

The above advantages were mainly evident when dealing with well-graded silty sands.

A noteworthy feature of the new traveling pluviator that sets it apart from existing ones is its ability to accommodate pluviation under evacuated conditions.
1 g Small-Scale Modelling of Saturated Cohesive Soils
Authors: Bray JD , Seed RB , Seed HB
Published: February 2009

This paper describes the use of 1 g small-scale models composed of weak, saturated clay mixtures to investigate the response of natural clay deposits to underlying base rock fault displacements. A 3:1 mixture of kaolinite and bentonite at water contents between 150 and 100% produces a material with undrained shear strengths on the order of 1 to 2.5 kPa and well-scaled stress deformation behavior for small-scale model testing without the need for a centrifuge apparatus. Strength testing indicated that the axial strain at failure could be controlled to evaluate the importance of this parameter in base deformation testing. It was found that the height of the shear zone in the saturated clay overlying the base rock fault offset was related to the magnitude of base movement and the failure strain of the soil.
A Coupled Heat and Water Flow Apparatus
Authors: Mohamed A-MO , Yong RN , Caporouscio F , Cheung SCH , Kjartanson BH
Published: February 2009

To study the performance of a compacted buffer material under thermal and isothermal conditions, a coupled heat and water flow apparatus is designed and presented. In the preliminary design, a one-dimensional flow of heat and water was not achieved. However, control of temperature gradient, existence of one-dimensional flow, and uniformity of temperature and volumetric water content distributions at any cross section within the specimen are achieved in the modified design.

Experimental results have shown that the temperature stabilizes very rapidly after a period of approximately 0.107 days. The moisture moves away from the hot end along the longitudinal direction of the specimen due to imposed thermal gradient. The time required for moisture to stabilize is in order of days.
Shear Strength Tests for Coarse Granular Backfill and Reinforced Soils
Authors: Bauer GE , Zhao Y
Published: February 2009

In order to overcome the limitations of the current standard small direct shear box in testing the shear strength of coarse granular backfill materials, a large direct shear apparatus (1000 by 1000 by 940 mm) was constructed at Carleton University and a series of direct shear tests were conducted with coarse granular soils. In addition, several direct shear tests on soils reinforced with geogrids were also conducted, and the shear strength parameters of the composites were compared with those of natural soils. It is shown that the controlled large direct shear test, though time consuming, provided a useful way of evaluating the behavior of the natural granular soils and reinforced soils.
Friction at the Cohesionless Soil-Structure Interface: Effect of Various Parameters according to a Classic Study and a New Approach
Authors: Abderrahim A , Tisot JP
Published: February 2009

A direct shear box, a ring shear apparatus, and a minipressuremeter are used: (1) to study the behavior of the cohesionless soil-structure interface; (2) to evaluate the friction mobilized at this interface. Tests have been carried out with a continual displacement of the structure in contact with the soil. The applied normal stress was kept constant during all tests. The influence of the mineralogy, the initial density, and the roughness are analyzed. The tests show that it is difficult to obtain identical laboratory results with different apparatus. It is necessary to validate these apparatus with the help of a comparison of in situ results. Once this validation is done, especially for the mini-pressuremeter, it is reasonable to consider the mini-pressuremeter for calibrating the structure in cohesionless soils.
Drift of Flush-Mounted Pressure Cell Readings
Authors: Filz GM , Duncan JM
Published: February 2009

Readings from earth pressure cells that were flushmounted in an instrumented retaining wall exhibited progressive change with time (drift) after backfill placement. The test procedures and conditions precluded the possibility that temperature effects could account for the drift. A series of experiments showed that the drift was caused by moisture migration from the backfill to the concrete retaining wall. It appears that the moisture causes a slight expansion of the concrete around the cells, resulting in distortion of the cells and decrease of the fluid pressure inside the cells. A surface treatment reduced the magnitude of the drift. A pressure cell design is proposed to mitigate this source of drift in new installations.
Notched Constant Tensile Load (NCTL) Test for High-Density Polyethylene Geomembranes
Authors: Hsuan YG , Koerner RM , Lord AE
Published: February 2009

A modification of an old test method, the notched constant tensile load (NCTL) test, is reintroduced to evaluate the stress-cracking performance of high-density polyethylene (HDPE) geomembranes. In this modified test, notched dumbbell-shaped specimens are subjected to a range of constant tensile loads in a 10% Igepal (CO-630) solution at 50°C. The method has been proposed to ASTM and is being considered by a task group within Committee D-35 on Geosynthetics. This paper presents the test procedures, results of a reproducibility study, and four sets of interlaboratory tests.
Geotechnical Tomography: The Effects of Diffraction
Authors: Potts BD , Santamarina C
Published: February 2009

Tomographic imaging is the inversion of a field parameter using boundary observations. Current techniques make different simplifying hypotheses. In geotechnical tomography the straight ray assumption is most common. Problems arise when the wavelength is of the same order of magnitude as the size of the inclusion. In this case, the physics of diffraction creates significant effects behind the anomaly, limiting the applicability of ray assumptions. This experimental study addresses the effect of diffraction and its potential consequences on inversion problems. The investigation is conducted using inclusion size to wavelength ratios between 1 and 10, with objects of various relative velocity and impedance. Travel times, power density, and signal duration are analyzed. Results demonstrate the healing effects of diffraction, frequency and impedance-dependent backscatter, and energy focusing. Hand-picked and cross-correlation-based travel times are compared. It is shown that both low- and high-velocity inclusions may become undetectable at some distance behind the object, that there is little effect of frequency on travel time but significant effect on power spectral density, and that high-velocity inclusions may be detected as low-velocity inclusions when travel time data are used.
Determination of Cation Exchange Capacity of Clayey Soils by the Methylene Blue Test
Authors: Cokca E , Birand A
Published: February 2009

The methylene blue adsorption test (MBAT) for determining the cation exchange capacity (CEC) of clays is described. An attempt has been made to respond to previously expressed uncertainties in the MBAT itself and then to apply this test to determine the CEC values of the three geologically different soil types encountered in Ankara (alluvial soils, terrace deposits, and residual soils).

Experiments with Na-montmorillonite, Ca-montmorillonite, illite, and kaolinite clays revealed that the MBAT method for determining the CEC of clays was simple and rapid and that the results were reasonable.
Bearing Capacity of Strip Foundation on Geogrid-Reinforced Clay
Authors: Shin EC , Das BM , Puri VK , Yen S-C , Cook EE
Published: February 2009

Laboratory model test results are presented for the ultimate bearing capacity of a strip foundation supported by a saturated clay layer reinforced by layers of geogrid. The tests were conducted in one type of clay. The average moisture content of the clay was varied, yielding varying undrained shear strengths. Laboratory tests were conducted to determine the critical nondimensional values for the depth and width of the geogrid reinforcement layers and also the location of the first layer of geogrid with respect to the bottom of the foundation to obtain the maximum possible bearing capacity ratio.
Prediction of Expansion Degree for Natural Compacted Clays
Authors: Basma AA
Published: February 2009

This paper presents a laboratory study aimed at developing a reliable method to predict the expansion degree of clays. The work herein is intended to complement, not replace, existing research in this area. Utilizing test data for 128 natural soils, a regression analysis was performed to assess the use of the liquid limit, the plasticity index, the percent clay, the percent colloids, and activity of a soil as single variables to estimate the swell potential under a 1-psi (6.9-kPa) pressure of a specimen compacted to maximum dry unit weight based on the standard AASHTO test at optimum water content. Through multiple regression analysis, combinations of the aforementioned variables were also used to evaluate the swelling potential and to predict the degree of expansion. These relationships were used to establish nomographic charts for quantitative and qualitative evaluation of swell characteristics. The results of the proposed charts are shown to be in good agreement with swell test data provided by various researchers.
Compressibility Characteristics of Gypseous Sandy Soils
Authors: AlNouri I , Saleam S
Published: February 2009

Soils containing gypsum as a cementing agent are affected considerably when subjected to changes in water content. Seepage through sandy gypseous soil causes serious damage to foundations built on such soils. A testing program was conducted on undisturbed soil specimens with three different gypsum contents to study the compressibility characteristics of such soils. The testing program included the following tests: standard consolidation, collapse, double oedometer, leaching, leaching collapse, and permeability.

The results revealed that the gypseous soil tested was a highly cemented sand whose compressibility depended on gypsum content. The behavior of this soil exhibited significant changes upon addition of water, especially when the process was accompanied by a continuous flow of water. The leaching process caused an increase in the value of the Compression Index. Furthermore, the soil exhibited what could be defined as “delayed compression,” whose rate was dependent on stress level and which increased upon leaching. The soil was found to be a “collapsible” soil, whose collapsibility increased significantly with leaching.
A Review of Instrumentation for Measuring Small Strains During Triaxial Testing of Soil Specimens
Authors: Scholey GK , Frost JD , Lo Presti DCF , Jamiolkowski M
Published: February 2009

Conventional procedures for determining deformations during triaxial tests are based on measurements made externally to the cell. This practice is inadequate, particularly if the small strain stiffness of the soil is being investigated, because errors are introduced which limit the accuracy and resolution of the measurements. The errors can only be eliminated if axial strains are determined internally, within the cell, and locally over the central one third of the specimen. Likewise, the radial dimensions should be monitored at specimen midheight. The last ten years has seen the introduction of a diverse range of small-strain measuring devices. This has been largely in response to recognition of the importance of achieving strain measurement accuracy of at least 10−3% for small-strain stiffness evaluation. This paper summarizes the types of instrumentation currently available and their modes of operation, benefits, capabilities, and limitations. Typical results comparing external and internal strain measurements are presented. A system for classifying internal-strain measuring devices is presented. It is anticipated that test results based on small strain determinations will be a more frequent requirement in the future. Accordingly, the paper is intended to assist prospective users in becoming familiar with the various techniques that have been used and presents information that should enable selection of appropriate equipment for particular applications. Given that improvements in existing systems are warranted, it is hoped that the paper will also provide stimulus for further research and development.
A Dual Interface Apparatus for Testing Unrestricted Friction of Soil Along Solid Surfaces
Authors: Paikowsky SG , Player CM , Connors PJ
Published: February 2009

A dual interface shear apparatus (simple or direct) was developed to evaluate the distribution and magnitude of friction between granular materials and solid inextensible surfaces. Ideal and natural granular materials were sheared along controlled and random solid surface geometries. The test results were evaluated through a model describing the interface friction mechanism based on a micromechanical approach. The influence of boundary conditions and interfacial shear modes was examined and compared to the results obtained in a modified direct shear box.

The test results show that the grain shape and the surface roughness, quantified with respect to the grain size, are the primary parameters controlling the interfacial shear strength at a given normal stress level. Three zones of normalized roughness associated with different shear strength levels were identified. These zones can be categorized into two possible shear mechanisms: interfacial and internal. The use of a small-size direct shear box (modified) to evaluate interfacial friction seems markedly influenced by the boundary conditions. The resulting interface friction angles exceed those that would develop along an unrestricted interface of soil and a solid surface, especially when shear takes place along the solid surface (e.g., smooth and intermediate normalized roughness). Erratum to this paper appears in 18(4).
The Rapid Determination of the Moisture-Retention Characteristics of Soil
Authors: Fourie AB , Papageorgiou G , Blight GE
Published: February 2009

A modified technique is described for determining the water-retention curve of a soil. The new technique allows the definition of a moisture-retention curve (typically six to seven data points) much more rapidly than is possible with conventional techniques such as the pressure plate apparatus. The full curve may be determined in four to six days compared with two to three weeks previously. Results are presented for three different soils. For one soil (a fly ash), comparative testing using the new technique and a conventional method shows good agreement. An added advantage of the new technique is that overall volume change of the soil specimen may be measured and not merely inferred from measurements of moisture outflow. Greater accuracy in determining the moisture-retention curve was thus obtained.
Geotechnical Properties of the Maryland-Sanders Lunar Simulant
Authors: Goodings DJ , Lin CP
Published: February 2009

Densely compacted Maryland-Sanders ground basalt was examined for the similarity of its geotechnical properties to those estimated for lunar regolith. Minimum and maximum densities fell within the upper range of those calculated to exist on the moon. Cone penetration resistances measured on specimens compressed to 80 and 100% relative densities bracket those reported for stress equivalent depths on the moon. The results of direct shear tests on specimens compressed to 100% relative density with normal stresses varying from 21 to 100 kN/m2 gave straight-line strength envelopes of c = 14 kN/m2 and φ = 39° for peak strength and c = 9 kN/m2 and φ = 37° for postpeak strength. Values of φ fall within the range of values extrapolated from lunar cone penetration tests, but values of cohesion are substantially greater. This difference is attributed to effects of test stress levels and soil anisotropy.
Alternative Test Method for Resilient Modulus of Fine-Grained Subgrades
Authors: Drumm EC , Li Z , Reeves JS , Madgett MR
Published: February 2009

The mechanistic design of flexible pavement systems requires the specification of mechanical properties for asphaltic concrete, base course, and soil subgrade. The stiffness of the soil subgrade is represented by the resilient modulus, Mr, which is determined in the laboratory from cyclic triaxial tests and is usually a function of the level of applied stress. For a typical pavement project where numerous soils are encountered, cyclic triaxial testing to determine Mr for each subgrade soil may be too complex and time consuming to be applicable on a production basis. Therefore, alternative methods for the determination or estimation of Mr are appropriate and are in fact suggested in the 1993 AASHTO Guide for Design of Pavement Structures (AASHTO Guide 1993).

An alternative test method (ATM) was developed based on a falling weight impacting a standard Proctor specimen. A simple theoretical model was used to develop expressions for the modulus and deviator stress as a function of the measured acceleration during impact. An analysis was conducted to compare the state of stress in the ATM with that in a subgrade under a pavement. A prototype device was constructed and used to estimate the resilient response of 14 soils for which standard cyclic triaxial data were available. The ATM results compared well with the results from standard triaxial tests, and the ATM was able to consistently distinguish the low resilient modulus soils from those with high modulus. The ATM was shown to provide results suitable for many design applications and may be useful for reducing the number of standard tests required to characterize the subgrade Mr response for a pavement project.
Tests on Model Jacked Piles in Calcareous Sand
Authors: Chin JT , Poulos HG
Published: February 2009

This paper presents the results of a series of displacement-controlled cyclic axial loading tests of model jacked piles in dry calcareous sand. The tests were conducted using a large test facility comprising a test chamber 1.0 m in internal diameter and 1.55 m in height. Model instrumented aluminum jacked piles 50 and 100 mm in diameter were used to investigate scale effects on the degradation of skin friction capacity under cyclic loading conditions. Test results are presented for the response during jacking (installation), initial static compression loading, cyclic loading, and post-cyclic static compression loading response. It is shown that the degradation of skin friction is governed by the “cyclic slip displacement” model.
Analysis of Hydraulic Gradient Effects for Laboratory Hydraulic Conductivity Testing
Authors: Fox PJ
Published: February 2009

A theoretical model is presented that characterizes the effect of hydraulic gradient on measured hydraulic conductivity in the laboratory. A closed-form equation is derived for the distribution of total head within a hydraulic conductivity test specimen as a function of specimen height, boundary stress conditions, compression index, and change of hydraulic conductivity index. From this expression, corresponding equations for the distributions of local pore pressure, effective stress, void ratio, hydraulic gradient, and hydraulic conductivity are presented. Two laboratory experiments were performed using a clay slurry to assess the validity of the theory: (1) an end-of-primary incremental loading consolidation test with direct hydraulic conductivity measurements, and (2) a rigid-wall hydraulic conductivity test with local pore pressure measurements. Using material properties obtained from the consolidation test, the theory predicted correctly the behavior of the hydraulic conductivity test specimen for two values of equivalent hydraulic gradient. It is concluded from this research that excessive hydraulic gradients applied during hydraulic conductivity testing can cause reductions in measured hydraulic conductivity. The magnitude of the effect is expected to be more important for normally consolidated soils with high compressibility, such as soft clays and soil-bentonite slurries.
Direct and Indirect Permeability of Fissured Tills
Authors: Hossain D
Published: February 2009

Comparison of direct and indirect measurements of water permeability on relatively large undisturbed and compacted Scottish till specimens in rigid-wall (Rowe cells) and flexible-wall (triaxial cells) permeameters shows the interaction of macro-fabric, test method, evaluation basis, effective stress, and possibly sidewall leakage. At low stresses, the sidewall leakage in a Rowe cell is the most likely cause of the directly measured permeability, kd, and pore-pressure-dissipation-based permeability, kp, becoming higher than settlement-based permeability, ks. Similarly, fissures raise permeability measured in both permeameters. Generally, kp is higher than ks (or volume-change-based kv from triaxial cells) with ka in between but closer to ks (or kv). The differences decrease with increasing stresses; the reduction rate for fissured specimens is dependent on fissure coating thickness and permeability.
Simplification of Soil Classification Charts Derived from the Cone Penetration Test
Authors: Zhang Z , Tumay MT
Published: February 2009

This paper presents a semi-empirical approach to simplify existing CPT and PCPT soil classification charts. This approach is based on two tendencies in current charts, namely soil type and in situ soil state. These charts may be simplified into one-dimensional soil classification systems by linear conformal mapping. Accordingly, several charts are simplified, and a comparison to in situ testing data indicates the conformity of the approach and formulas suggested. The simplified systems allow users to identify and describe in situ soil types (site stratigraphy) in a visualized or graphic manner. The results also display the overlaps among different soil types in a cone soil classification.
Rigorous Theoretical Analysis of a Flow Pump Permeability Test
Authors: Esaki T , Zhang M , Takeshita A , Mitani Y
Published: February 2009

With the growing importance of environmental issues in our society, extremely low-permeability geotechnical materials are being studied increasingly for their long-term stability and effectiveness in retarding the transport of hazardous wastes. Relatively rapid measurements of the permeability and specific storage of the materials, using relatively low hydraulic gradients, can be obtained with a constant flow pump and the corresponding theoretical analysis proposed by Morin and Olsen (1987). However, the accuracy of this method is limited because their theoretical analysis does not take into account the storage capacity of the experimental system. This paper presents a more general theoretical analysis and shows how it can be used to determine not only the permeability and specific storage of a test specimen, but also the storage capacity of the experimental system. Experimental data are presented that illustrate the accuracy and efficiency of the general theoretical analysis.
Evaluation of Sulfate Expansion in Soil-Cements
Authors: Ksaibati K , Huntington GS
Published: February 2009

This paper presents the results of an evaluation of internal sulfate attack in soil-cements. Differences in rates and amounts of expansion were evaluated for several aggregate types. Sulfate expansion of soil-cement was evaluated using a modified version of ASTM Test Method for Length Change of Hardened Hydraulic Cement Mortar and Concrete (C 157) that utilized a falling weight compaction procedure and large 76 by 76 by 286-mm bars. This paper compares this new test procedure with already established means of evaluating internal sulfate expansion of soil-cement. Expansion of small 25 by 25 by 286-mm bars compacted with a hand tamper was compared to expansion of the large bars compacted by a falling weight. Some small bars were cured in lime-saturated water, while others were cured in humid air. Much better results were achieved when curing took place in water. The new large bar method simulated field expansions better than the small bars. The use of small bars cured in lime-saturated water is recommended only when results are needed quickly. Large bars cured in water are recommended whenever time permits.
Rock Porosity Determinations Using Particle Densities Measured in Different Fluids
Authors: Passas N , Butenuth C , de Freitas MH , Bunatova V
Published: February 2009

Rock porosity, when calculated from measurements of bulk and particle rock density, is found to depend on the method used to determine these densities. The particle density, which is found experimentally, varies with the immersion fluid used; hence, the porosity determined depends on it, too. Organic fluids are recommended in standards for describing particle density for special applications; however, water is generally considered to be virtually inert when in contact with inorganic particles, particularly if the particles are composed of silicates. Thus, the results of measurements made using water as the immersion liquid are not considered to have been measurably affected by water. This paper shows that water does, in fact, alter measurably the value of silicate particle density obtained compared with measurements made using an organic fluid, viz., n-heptane. Explanations for this finding are under further consideration.
Round Two—Confined Compression: Young's Modulus, Poisson's Ratio, and Ultimate Strength
Authors: Pincus HJ
Published: February 2009

The Institute for Standards Research interlaboratory study of rock properties has provided precision statements for two additional ASTM rock-property test methods, D 5407 (Young's modulus and Poisson's ratio) and D 2664 (ultimate strength), both in confined compression. Three types of intact rock, Barre Granite, Berea Sandstone, and Tennessee Marble, were used in this study. Data were collected for both test methods at confining pressures of 10, 25, and 40 MPa, with four replications per rock type. The rock testing was preceded by pilot testing for Young's modulus and Poisson's ratio on aluminum alloy 2024 T351, with three replications. Young's modulus and Poisson's ratio were evaluated, for both aluminum and rock, from stress-strain data for the intervals from 25–50% and 40–60% of the maximum differential stress. Seven laboratories produced pilot data, and six of these laboratories produced data on rock for this report. Both the aluminum and rock specimens were prepared at central locations and were furnished ready for testing to the participating laboratories. For both elastic moduli, the overall normalized repeatability limit (“within laboratory”) for rock is about twice that for aluminum; the overall normalized reproducibility limit (“between laboratory”) for rock is about the same as that for aluminum.
A Circular Arc Test for Soil-Geosynthetic Interface Strength
Authors: Ghiassian H , Hryciw RD , Gray DH
Published: February 2009

A circular arc test is described for determining the residual, or constant volume, interface strength parameters between soil and geosynthetics. The model is based on the variation of tension in a circular arc of fabric placed over a soil specimen and dead-loaded on two ends. The test method is simple and boundary conditions are well defined. The apparatus, theoretical formulation, and testing procedures are presented. The interface friction angle between dry Muskegon sand and three different materials: a cotton fabric, a fiber-glass mesh, and a nonwoven Geolon N35 filter, as determined by the circular arc test, are presented. Results of a staged circular arc test are also presented for the cotton fabric, and comparison to direct shear test results is made.
Development of an Accelerated Creep Testing Procedure for Geosynthetics—Part I: Testing
Authors: Farrag K , Shirazi H
Published: February 2009

The prediction of the long-term strength of geosynthetics is usually based on 10,000-h extension creep tests. Creep tests at elevated temperatures can accelerate testing duration to a reasonable time frame (1000 h) and the results can be extrapolated to longer time intervals. The paper presents the current state of practice in creep testing of geosynthetics and the development of testing equipment and procedure for accelerated creep tests at elevated temperatures. Creep tests were performed on high density polyethylene (HDPE) and polyester (PET) geogrids typically used in soil reinforcement applications.

Creep behavior at room temperature was first evaluated in 10,000-h tests at various creep loading levels (10 to 45% of ultimate strength of the geogrid Tmax). Accelerated creep tests were then conducted for 1000 h at various controlled temperatures from 24°C (75°F) to 72°C (160°F). These tests were conducted at the same loads to evaluate time-temperature-creep relationships of the geogrid.
Automatic Volume Measuring Device for Testing Dry Soils: “Martina”
Authors: Fioravante V , Capoferri R
Published: February 2009

A new automatic measuring device for testing dry granular soils in laboratory is presented. The device enables direct measure of volume changes of dry specimens by measuring gas that comes out or in during testing due to soil deformability. As the soil deforms, voids (which are supposed to be hydraulically connected to each other) change their volume; if they are part of a closed hydraulic circuit (any leakage is avoided) and gas pressure is kept constant by adjusting the total volume of such circuit, the amount of gas through soil voids is transferred to the measuring device, which varies its volume. The apparatus is described in detail as to its working principle. A strong effort was made to assess errors and to calibrate such apparatus as well as to evaluate its precision when used for triaxial testing. Finally, to validate its behavior, the most significant results obtained comparing dry versus saturated granular soil triaxial tests are here presented.
Compaction of Sand-Processed Clay Soil Mixtures
Authors: Howell JL , Shackelford CD , Amer NH , Stern RT
Published: February 2009

The effects of type of processed clay soil, curing period, and mixing procedure on laboratory compaction of sand-attapulgite clay (S-AC), sand-granular bentonite (S-GB), sand-powdery bentonite (S-PB), and sand-attapulgite clay-granular bentonite (S-AC-GB) mixtures are evaluated. Compaction is evaluated for total clay soil contents of 10, 15, and 20%. Different trends in optimum water content, wopt, and maximum dry unit weight, γdmax, versus clay soil content among the S-AC, S-GB, and S-PB mixtures are attributed, in part, to (1) the greater water sorptivity and lower swelling potential of attapulgite clay relative to the bentonites, (2) the larger particle sizes of the granular bentonite in the air-dried condition relative to the powdery bentonite, and (3) the possible correlation between the wopt and the plasticity index of the sand-bentonite mixtures. The Δwopt values and Δγdmax values resulting from one-day versus seven-day curing periods before compaction of the S-GB and S-PB mixtures are ∼0.5 percentage points and ≤0.08 kN/m3 (≤0.5 pcf), respectively, and result in different trends in γdmax versus bentonite content for the two types of sand-bentonite mixtures. Also, mixing the sand and bentonite in a dry condition before adding water consistently results in greater wopt and γdmax values than mixing the sand with the appropriate amount of water before adding the bentonite regardless of the type of bentonite. Finally, mixing the attapulgite clay and granular bentonite together in small amounts for each individual compaction point for the S-AC-GB mixtures consistently results in higher γdmax and wopt values relative to mixing the attapulgite clay and granular bentonite together in large amounts sufficient to cover all compaction points.
Development of an Accelerated Creep Testing Procedure for Geosynthetics, Part II: Analysis
Authors: Farrag K
Published: February 2009

A procedure for extrapolating creep strains to longer time intervals was developed. The procedure was based on applying time-shift factors to creep strain curves at elevated temperatures to establish a master strain curve for longer time intervals. The procedure was applied to creep test results on high density polyethylene (HDPE) geogrid tested at creep loads up to 40% of its maximum tensile strength Tmax and at temperatures up to 72°C (160°F). Temperature creep curves of 1000-h tests were shifted along the log-time scale to create 10 000-h master strain curves at each loading level. The established master curves were compared with experimental results of 10 000-h creep tests at room temperature and at the same loading levels. The shift factors were then applied to the creep curves to predict creep response for a duration of more than 100 000-h (about two cycles shift on the log-time scale from the initial 1000-h tests).

The analysis demonstrated the applicability of applying shift factors to elevated-temperature creep test results to predict the response at longer times for this type of geogrid. The analysis was applicable to creep loads up to 40% Tmax. The procedure, however, did not accurately estimate creep response at higher loading levels and temperatures where accelerated creep failure occurred.