Automation and further development of the borehole shear test

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Bechtum, Theodore
Iowa State University; Digital Repository @ Iowa State University
borehole shear test; BST
thesis / dissertation description
The purpose of this work was to automate and further develop the borehole shear test (BST). The description of the successful automation procedure is presented, and investigations into soil displacement and cyclic BST loading are described. Displacement and cyclic loading investigations were performed with additional instrumentation to measure soil displacement, and modifications were created for the basic testing procedure. Numerical analysis was utilized to determine the stresses and strains created during a monotonic test in dry sand. Automated monotonic testing was successfully performed on a variety of soil types. Significant potential exists for a cyclic BST, and a starting point for future efforts to standardize and gain acceptance for the cyclic process is provided. Findings include comparisons between the shear displacement behavior obtained with direct shear tests and borehole shear tests. Additionally, cyclic stress records obtained with the automated BST are analyzed and found to correspond to expected soil behavior.