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Geotechnical testing journal
American Society for Testing and Materials
Geotechnical testing journal

American Society for Testing and Materials

季刊

0149-6115

Geotechnical testing journal/Journal Geotechnical testing journalSCI
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    Editorial: 2024 Reviewer Thank Yous

    1179-1180页
      原文链接:
    • NETL
    • NSTL

    A 4D Soil-Structure Interaction Model Testing Apparatus

    Thomas RiccioTomas RomeroMarco PrevitaliMiguel Mánica...
    1181-1204页
    查看更多>>摘要：A new three-axis loading frame has been developed to enable real-time visualization of in situsoil and rock structure interactions via X-ray tomography during small-scale model testing. Theconstructed frame is capable of performing a wide range of small-scale 1g tests and can accommodatemonotonic and cyclic actuation under both load and displacement control. Thecompact size of the system enables remote multi-axis operation from within an X-raycone-beam scanning bay, a capability which is owed to a comprehensive design process.Design and fabrication involved a blend of physical and numerical experiments to assess suitableconstruction materials and performance. In this scope, the new equipment is discussedand its capability is showcased.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    A Hydraulic Gradient and Stress-Controlled Erosion Apparatus for Assessing Soil Internal Erosion

    Didier MarotBikram OliFateh BendahmaneRachel Gelet...
    1205-1228页
    查看更多>>摘要：Among the four dominant mechanisms of internal erosion, suffusion appears as one of themost complex. It is indeed the result of the combination of three processes: dislodgementof fine particles, transport of them, and filtration of some fluidized fine particles. These processesdepend on the soil’s stress state and on the hydraulic gradient path. Thus, to ensure therepeatability of the suffusion test and to study with accuracy the influence of the aforementionedparameters, a new apparatus was developed. This apparatus is designed to test specimensunder a vertical downward flow in hydraulic gradient controlled condition whilecontrolling the confining pressure and the stress deviator, which can be either positive or negative.Ten tests on one cohesionless soil were performed in triaxial conditions, with the samemean effective stress and four different values of stress deviator. To compare with conventionalsuffusion results, one test is also performed in rigid wall conditions. For all performedtests, the same hydraulic gradient path was applied and particular attention is paid to the repeatability,which implies control of each test step. At the end of each test, the specimen wasdivided into four layers to measure post-suffusion grain size distributions. The time evolutionsof the hydraulic conductivity and the erosion rate permit to identify four different phases. Eachphase is characterized by two methods: one based on the hydraulic gradient and the secondbased on the expended energy by the fluid. The results show the great influence on the suffusionkinetics of the preferential flow paths, which localize in the body of the specimen intriaxial conditions and on the circumference in rigid wall ones. Under a constant mean effectivestress, the effect of the stress deviator on the suffusion kinetics appears limited, for the testedsoil and shear stress ratios.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    Direct Shear Testing Apparatus for Saturated Rock Joints

    Kyungsoo HanLaura J. Pyrak-NolteAntonio Bobet
    1229-1242页
    查看更多>>摘要：A novel shear test apparatus has been designed and built to test saturated jointed rock specimensunder normal and shear loading, capable of housing seismic transducers to monitorsimultaneously the mechanical and geophysical response of the rock joints during shear.The system comprises a sealed pressure chamber and a biaxial compression frame. The internaldimensions of the chamber are 177.8 mm × 228.6 mm × 381.0 mm to accommodate a rockspecimen with dimensions 152.4mm× 127.0 mm× 50.8 mm. The chamber ismade of aluminumto reduce its weight and is designed to sustain a maximum chamber pressure of 10 Mpa, whichis considered sufficient to be able to saturate a wide number of rocks. Structural calculations ofthe chamber are performed with the finite element method (FEM) software, ABAQUS, with thecriterion of a maximum deflection of 1 mm at maximum chamber pressure, which is smallenough to prevent the loss of seal between the loading shafts and the chamber. The rocksused in the study are Indiana limestone and Sierra White granite. B-value tests conductedon cylindrical specimens of the rocks placed inside the chamber show that the back pressuresrequired to achieve saturation are 3.5 Mpa for Indiana limestone and 5.0 Mpa for Sierra Whitegranite. The chamber performance has been evaluated by comparing the changes of volume ofthe chamber at different pressures, measured in the laboratory, with those predicted withABAQUS. The successful completion of a number of repeatable direct shear tests, on tensile-induced rock joints in dry and saturated conditions specimens, has further establishedthe correctness of the chamber design and its operation.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    Effect of Testing Mechanisms on the Load-Strain-Time Behavior of Geosynthetic Reinforcements

    Rafael Ribeiro PlácidoFernando Henrique Martins PortelinhaMarcos Massao FutaiTiago de Jesus Souza...
    1243-1259页
    查看更多>>摘要：This study compares how geosynthetics behave under load, under strain, and over time whensubjected to confined tensile tests in soil, employing two commonly used mechanisms inresearch. One test type simulates a reinforced layer, where tensile loads are indirectly appliedto the geosynthetic via stresses transferred from the soil. In contrast, the other test appliestensile loads directly to the geosynthetic material using clamps while under soil confinement.The objective is to elucidate how these testing mechanisms might yield differing in-soil tensilecharacteristics for different geosynthetics. The study involved conducting load-strain-timetests on samples of nonwoven and woven geotextiles, as well as a geogrid, under varyingsustained loads over a 120-h period within a sand clay soil providing soil confinement to geosyntheticsat different surcharge levels. The results suggest that soil confinement plays a significantrole in shaping the load-strain-time behavior of geosynthetics. Furthermore, it wasnoted that the impact of testing mechanisms on this behavior is contingent upon the typeand stiffness of the geosynthetics, as well as their interaction with the confining soil. In general,in-soil tests in which tensile loads are mobilized by geosynthetics and transferred from the soilprovide more confident results for better simulating operation conditions. Tests that directlyapply tensile loads to the geosynthetic while maintaining stationary soil confinement may yieldmisleading results, especially for geosynthetics that have poor interaction with the soil.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    Examination of the Dry Density Importances in TDR Use and of the ASTM D6780 Standard Based on a New Calibration Procedure

    Shay Nachum
    1260-1274页
    查看更多>>摘要：The use of time domain reflectometry (TDR) to monitor soil water content at either field orlaboratory scales is highly common. Regarding the soil dry density, ρd, effect on the TDR application,three main approaches are found in the literature: (1) Ignore the density issue and usecalibration to evaluate the water content regardless of the density. This approach is basic, yetcommon. (2) Include soil density in the calibration equation and use calibration for the watercontent as a function of both the TDR output and soil density. In this approach, the soil densityshould be provided from an independent source. (3) Determined ρd from the TDR waveform. Inthis case both water content and ρd are set from the TDR analysis. In cases where the ρd is notavailable, in order to use TDR for water content measurement, a decision has to be madewhether to address the density issue although it requires resources, or to neglect it. This articlereviews this issue and validates the density effect using an efficient TDR calibration methodology.A calibration scheme that controls ρd of the specimen has been developed and applied.The methodology creates continuous calibration curves over a range of volumetric water contentfrom a single test specimen. Based on the results, it has been demonstrated that the soildensity has a major effect on the TDR output and it cannot be ignored. In addition, this articlepresents a unique examination of ASTM D6780, Standard Test Methods for Water Content andDensity of Soil In Situ by Time Domain Reflectometry (TDR). The ASTM dry density estimationwas found to provide reliable results; however, the gravimetric water contents estimation givesunsatisfactory results, especially for low densities.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    FEM Analysis on Isotropic Consolidation of Unsaturated Soils Using Ceramic Disks and Microporous Membrane Filters for Suction Control

    Xi XiongShun-ichi KobayashiHiroyuki IzumiFeng Zhang...
    1275-1297页
    查看更多>>摘要：Microporous membrane (MM) filters with a significantly thin thickness have recently been usedas an alternative to ceramic disks for matric suction control in the axis-translation technique forelement tests on unsaturated soils. Although researchers have highlighted some discrepanciesin test results when ceramic disks and MM filters are used, the mechanism leading to thesediscrepancies has not yet been clarified. In this study, suction-controlled triaxial tests werefirst conducted on unsaturated completely decomposed granite using two filters. Then, it isnatural to believe that the different thicknesses of ceramic disk and MM filters may significantlyinfluence the suction equilibrium process of specimens. To clarify this issue, soil-water-aircoupled finite element modeling was performed to simulate the consolidation process in triaxialtests as an initial/boundary value problem. In the numerical calculation, the influence ofthe void ratio on the water retention curve (WRC) of soil was properly considered by adoptinga deformation-dependent WRC model. In particular, the ceramic disk and MM filter, along withthe specimens, were modeled, and their differences in thickness were considered. The calculatedresults show that a nonuniform distribution of suction occurred in the ceramic disk, leadingto greater drainage discharge of the specimens. In other words, the influence of thethickness difference between the MM filter and ceramic disk cannot be neglected. However,regardless of whether ceramic discs or MM filters are used, the uneven distribution of the statevariables in the specimens may occur in the triaxial tests for unsaturated soils, which emphasizesthe importance of assessing the soil tests using the present axis-translation technique asinitial/boundary value problems.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    Modified Complex Electrical Resistivity Technique: Applications to Saturated and Unsaturated Soils

    Kyle ParrStacey E. KuleszaMichelle L. Bernhardt-Barry
    1298-1312页
    查看更多>>摘要：Direct current (DC) electrical resistivity is a common laboratory soil characterization method tosupport geotechnical infrastructure design and to supplement site investigations. The complexelectrical resistivity method has the potential to provide additional electrical soil properties toenhance electrical soil characterization. Both methods are conventionally performed underfully saturated soil conditions; however, many environments exist where soil is not fully saturated,such as ballast structure supporting railways. In this study, a new experimental setupfeaturing a current enhancing agent (agar) for complex electrical resistivity testing is evaluatedby testing five different soil specimens reconstituted at saturated and unsaturated conditions.Results showed that the new experimental setup is valid and can be used to obtain repeatmeasurements, particularly for specimens reconstituted in the unsaturated conditions wherethe traditional DC electrical resistivity setup yields results that are unreliable. This is one of thevery few studies where tolerances for triplicate specimens are reported to establish differencesin measurements from sample preparation versus discernable variability between differentgeomaterials. Additionally, all results are supported by a Cole-Cole model. The results showthat the additional data collected in a complex electrical resistivity test can be used to differentiatedifferent soil types that are ambiguous with the DC electrical resistivity method. Theadditional data have the potential to more fully characterize the electrical properties of saturatedand unsaturated soils, as well as to help distinguish unique geophysical signatures ofvarious geomaterials to enhance a geophysical site investigation for identifying soil variabilityin the subsurface.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    A Method for Determining Yield Stress of Unsaturated Soils from Lateral Pressure

    Yan LiuXiang WangYuxin ZhaoLihong Chen...
    1313-1327页
    查看更多>>摘要：Predicting the stress–strain behavior of unsaturated soils is essential for determining yieldstress. This paper explores a new method for determining the yield stress of unsaturated soilsfrom the lateral pressure curve. A series of earth pressure at rest (K_0) ondometer tests wereconducted on unsaturated Yangqin silt clay. Lateral stress was obtained under different saturationsand compactness. The relationship curves between lateral and vertical net stress weredrawn for each condition. An obvious turning point was observed in the curve, which can beused to determine the yield stress. The oedometer tests were conducted, and the Casagrandeand the bilogarithmic methods were used for comparison purposes. The difference betweenthe proposed and traditional methods was less than 17 %. The initial saturation and compactnessinfluence on the yield stress was discussed. The yield stress increased with the decrease insaturation and increases in compactness, which is consistent with that of the classic method.The test results and comparison prove the rationality of the proposed method. No coordinatetransformation is required in the proposed method, which is more convenient for data processing.It can be used to determine the yield stress of unsaturated soils from another perspective.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials

    Application of Asaoka’s Method in Multistage Triaxial Compression Testing of Normally Consolidated Soils

    K. P. LijithR. G. Robinson
    1328-1343页
    查看更多>>摘要：Determination of shear strength parameters becomes a challenge when it is difficult to retrievea minimum of three identical undisturbed soil specimens. In such a situation, multistage triaxialcompression testing can be adopted using a single specimen. Multistage triaxial testing involvesstage-wise consolidation and shearing at three confining pressures without the failureof the specimen until the last stage. A critical issue associated with multistage triaxial testing isthe estimation of ultimate deviator stress and the corresponding pore pressure as the specimenwas not allowed to reach failure in each stage. Conventionally, the failure stress state ineach stage is computed by extrapolating the stress–strain and pore pressure–strain data toa finite strain by employing Kondner’s rectangular hyperbola model. However, it is reportedin the literature that the aforementioned method often overestimates the deviator stress andpore pressure values. In this context, the present study investigates the suitability of Asaoka’sobservational procedure for predicting these values at failure state. The validity of theproposed procedure is verified by comparing the ultimate deviator stress and pore pressurevalues obtained by analyzing the stress–strain data collected from the literature and by performingmultistage triaxial testing on three reconstituted soil samples with that of the rectangularhyperbola method. From the results, it was observed that Asaoka’s method is moresuited for predicting the shear strength parameters. It is believed that the proposed methodologywould aid in obtaining the shear strength parameters of a soil from a single specimen byconducting multistage triaxial testing.
      原文链接:
    • NETL
    • NSTL
    • Amer Soc Testing Materials