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

Sachan, Ajanta; Penumadu, Dayakar

doi:10.3208/sandf.47.67

Cited by 33 publications

(10 citation statements)

References 24 publications

(27 reference statements)

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“…As a result, the proportion of platelet edges in the axial direction increased as the shearing progressed, and resulted in relatively higher intensity of prism peaks when the X-rays interacted with the sample from top or bottom. Sachan and Penumadu (2007c) that the inclination of shear band from horizontal direction was observed to be lower in extension shearing as compared to compression shearing. As a result, the particles along the shear band after extension shearing showed a larger number of edges of particles in the side sample, which led to the high intensity prism peaks in their XRD pattern and exhibited large PR value.…”

Section: Xrd Results For Clay Samples Havingmentioning

confidence: 81%

“…A possible reason behind this observation could be that the triaxial testing system used in this study allowed loading piston to apply the external force on the soil specimen from its top surface during shear deformation process, which might cause a small variation in the mode of localized deformation or differences in local strain profile at top and bottom of the specimen (Sachan and Penumadu 2007c). As a result, the reorientation of clay platelets during shear deformation within the top sample would exhibit higher intensity prism peaks in comparison to the bottom sample.…”

Section: Xrd Results For Clay Samples Havingmentioning

confidence: 94%

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Effect of Shear Deformation on Microfabric of Clay Using XRD Technique

Sachan

Penumadu

2008

Geotech Geol Eng

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The present paper deals with the impact of shear deformation on the geometric arrangement of particles within the soil specimen, which is termed as the microfabric of soil. A series of compression and extension lubricated end triaxial tests are performed on cylindrical specimens of Kaolinite clay with two extreme microfabrics; dispersed and flocculated, which are obtained using slurry consolidation technique. Flocculated microfabric has random orientation of particles within the soil mass having face-to-edge particle contacts; however, dispersed microfabric has parallel orientation of particles containing face-to-face particle contacts. When the specimen is subjected to large stress levels during its shear deformation, the particle orientation and the geometric arrangement within the soil specimen gets affected due to the force acting on the clay platelets. The variation in microfabric of soil before and after shear deformation process is evaluated by obtaining X-ray diffraction patterns of the clay specimen at three different locations using standard X-ray diffractometer. The discussion includes an analysis of the orientation of soil particles located at shear banding zones of the clay specimens, which may be useful for understanding the strain localization development in clays.

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Section: Xrd Results For Clay Samples Havingmentioning

confidence: 81%

Section: Xrd Results For Clay Samples Havingmentioning

confidence: 94%

Effect of Shear Deformation on Microfabric of Clay Using XRD Technique

Sachan

Penumadu

2008

Geotech Geol Eng

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“…Digital image analysis (DIA) is an approach to make measurements using images captured by digital cameras [12,13,25,35]. However, when a photograph is taken for a 3D object using a digital camera, a 2D image is obtained and the depth of the object is lost.…”

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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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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“…Stamps and latex shell influence in the triaxial machine is well known [4,5]. Also, many investigators tried to reduce such influence by adding a sliding interface between specimen and triaxial machine stamps [4,6,7,8]. However, it is necessary to use model parameters, which simulate a soil behavior only.…”

Section: Fig 1 Triaxial Machine (Npo «Geotek») and Its Principal Smentioning

confidence: 99%

Evaluation of Stamps and Latex Shell Influence on Stabilometer Testing Results, Modeled with Simulia Abaqus

Volik¹

2011

geomate

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Triaxial tests are often used, along with other research methods, in order to define parameters of geotechnical data. The main topic being conferred in work is analysis of influence, exerted by stamp and latex shell, upon the results of triaxial machine soil tasting. The stabilometer modeling and verification was produced. Calibration of soil model parameters, derived from triaxial tests, is brought in work. The necessity of three dimensional simulation of soil testing process is pointed out in order to take into account stamp and shell influence.

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

Cited by 33 publications

References 24 publications

Effect of Shear Deformation on Microfabric of Clay Using XRD Technique

Effect of Shear Deformation on Microfabric of Clay Using XRD Technique

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

Evaluation of Stamps and Latex Shell Influence on Stabilometer Testing Results, Modeled with Simulia Abaqus

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