Strain Localization in Combined Axial-Torsional Testing on Kaolin Clay

Lin, Hung-Hsi; Penumadu, Dayakar

doi:10.1061/(asce)0733-9399(2006)132:5(555)

Cited by 37 publications

(27 citation statements)

References 12 publications

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“…Considering that the accuracy of volume change measurements by directly monitoring water volume changes is about 0.25 % [14], it is concluded that the proposed method can produce results comparable to those obtained from the conventional direct measurement of water volume changes. A numerical interpolation technique similar to that in Lin and Penumadu [24] is used to generate a continuous deformation field from the obtained discrete points on the specimen surface. Figure 19 shows the vertical strains developed in the soil specimen at different vertical displacement levels.…”

Section: Test Results On the Saturated Sandmentioning

confidence: 99%

“…Gachet et al [12] applied the DIA method to determine volume changes of an unsaturated soil from its lateral profiles. Lin and Penumadu [24] used a method similar to Park [28] to analyze a series of combined axial-torsional tests for kaolin clay under undrained conditions. For the measurement points on a specimen surface with spacing of 10 mm, the obtained accuracies of measurement are 0.2 and 0.3 mm in the vertical and circumferential direction, respectively.…”

Section: Digital Image Analysis With Refraction Correctionmentioning

confidence: 99%

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A photogrammetry-based method to measure total and local volume changes of unsaturated soils during triaxial testing

Zhang

Chen

et al. 2014

Acta Geotech.

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Triaxial tests have been widely used to evaluate soil behaviors. In the past few decades, several methods have been developed to measure the volume changes of unsaturated soil specimens during triaxial tests. Literature review indicates that until now it remains a major challenge for researchers to measure the volume changes of unsaturated soil specimens during triaxial testing. This paper presents a non-contact method to measure the total and local volume changes of unsaturated soil specimens using a conventional triaxial test apparatus for saturated soils. The method is simple and cost-effective, requiring only a commercially available digital camera to take images of an unsaturated soil specimen during triaxial testing from which accurate 3D model of the soil specimen is reconstructed. In this proposed method, the photogrammetric technique is utilized to determine the orientations of the camera where the images are taken and the shape and location of the acrylic cell, multiple optical ray tracings are employed to correct the refraction at the air-acrylic cell and acrylic cellwater interfaces, and a least-square optimization technique is applied to estimate the coordinates of any point on the specimen surface. The paper first discusses the theoretical aspects of the proposed method. An image analysis on a caliper was then used to evaluate the accuracy of photogrammetric analysis in the air. A series of isotropic compression tests on a stainless steel cylinder were used to demonstrate the procedure and evaluate the accuracy of the proposed method, while triaxial shearing tests on a saturated sand specimen were used to exam the capacity of the proposed method for measuring the total and localized volume changes during triaxial testing. Results obtained from the validation tests indicate that the accuracy for the photogrammetry in the air is about 10 lm. The average accuracy for single point measurements in the triaxial tests ranges from 0.056 to 0.076 mm with standard deviations varying from 0.033 to 0.061 mm. The accuracy for total volume measurements is better than 0.25 %.

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Section: Test Results On the Saturated Sandmentioning

confidence: 99%

Section: Digital Image Analysis With Refraction Correctionmentioning

confidence: 99%

A photogrammetry-based method to measure total and local volume changes of unsaturated soils during triaxial testing

Zhang

Chen

et al. 2014

Acta Geotech.

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“…3(b)) in order to determine true specimen dimensions and grid point positions. By incorporating Snell's law of refraction, a 2-D correction model (Parker, 1987;Lin and Penumadu, 2005) was developed to describe the relationship between the observed and actual specimen measurements. This model was used in this study to obtain the true position and displacement of tracking dots on the surface of cylindrical specimens.…”

Section: Digital Image Analysis (Dia)mentioning

confidence: 99%

“…If the stress and strain states were interpreted at the stage of shear band formation ignoring the fact that the strain localization would have already taken place, the interpreted stress and strain would be inaccurate. Lin and Penumadu (2005) studied the strain localization patterns of hollow cylindrical specimens sheared under combined axialtorsional loading conditions using digital image analysis (DIA) technique. They developed an experimental setup for DIA technique, a procedure for digital data processing, and a program for data interpolation; which was used in this study to produce the strain contour plots and study the initiation and propagation of strain localization within the specimen.…”

Section: Introductionmentioning

confidence: 99%

Strain Localization in Solid Cylindrical Clay Specimens Using Digital Image Analysis (DIA) Technique

Sachan

Penumadu

2007

Soils and Foundations

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“…Generally, soil failure occurs with the formation and development of one or more shear bands [1]. Applying a load to a soil element causes spatially non-uniform deformation that gradually focuses on a specific shear band [2]. When the load exceeds the soil element's shear strength, progressive failure (i.e., shear failure) occurs along the shear band where the deformation is concentrated.…”

Section: Introductionmentioning

confidence: 99%

Shear Band Characterization of Clayey Soils with Particle Image Velocimetry

et al. 2020

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Identifying the spatial distribution of deformation and shear band characteristics is important for accurately modeling soil behavior and ensuring the safety of nearby geotechnical structures. However, most research on the shear behavior of soils has focused on granular soil and clay-rich rocks, with little focus on clayey soil, and the entire shearing process from the initial state to failure has not been observed. This study evaluated the spatial distribution and evolution of deformation in clayey soils from the initial state to the post-failure state and the shear band characteristics. Plane strain tests were performed on normally consolidated and over-consolidated clay specimens, and digital images were captured through a transparent side wall for particle image velocimetry (PIV) analysis. PIV was performed to evaluate the displacement and deformation of soil particles. The results show that the shear-strain behaviors of two clays during the shearing process could be divided into four stages: initial, peak, softening, and steady state. Shear bands were observed to form in the softening stage, and the shear band slopes were compared to values in the literature. These results can be used to characterize shear bands in clay as well as predict failure behavior and guide reinforcement at actual sites with soft ground.

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Strain Localization in Combined Axial-Torsional Testing on Kaolin Clay

Cited by 37 publications

References 12 publications

A photogrammetry-based method to measure total and local volume changes of unsaturated soils during triaxial testing

A photogrammetry-based method to measure total and local volume changes of unsaturated soils during triaxial testing

Strain Localization in Solid Cylindrical Clay Specimens Using Digital Image Analysis (DIA) Technique

Shear Band Characterization of Clayey Soils with Particle Image Velocimetry

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