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The study of shear and longitudinal velocity measurements of sands and cohesive soils

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dc.contributor.advisor John T. Germaine. en_US Marjanovic, Jana en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. en_US 2012-10-26T19:01:54Z 2012-10-26T19:01:54Z 2012 en_US 2012 en_US
dc.description Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012. en_US
dc.description Cataloged from PDF version of thesis. en_US
dc.description Includes bibliographical references (p. 185-189). en_US
dc.description.abstract This thesis evaluates some methods for the measurement of stiffness parameters of soils, with an emphasis on the use of bender element technology in obtaining the shear modulus. The experimental program consisted two primary stages. The beginning part of the experimentation was concerned with evaluating the behavior of bender elements, both free-standing and when applied to soil. For this case, experiments were performed on dry Ticino sand. It was concluded that the bender element tip geometry has a much greater impact than previously perceived, in particular with long, slender geometries sometimes creating directly-propagating compressional waves that interfere with the shear wave arrival detection. To reduce the uncertainty in signal interpretation, a specimen aspect ratio of 1 was adopted, with a minimum wavelength ratio of 2. The second part of the experimentation consisted of using bender elements on Boston Blue Clay, both intact samples as well as Resedimented Boston Blue Clay, created in the laboratory from processed powder. The results obtained from loading normally consolidated specimens were generally consistent and in good agreement with the literature. The unloading portion was observed to behaves differently as a function of maximum consolidation stress, with the shear modulus decreasing less during unloading as higher stress ranges are reached. In addition to the testing performed on soils, a parametric study was conducted on common materials including steel, aluminum, acrylic, and rubber in order to evaluate the results for stiffness parameters measured using extensometers, accelerometers, and ultrasonic P-wave transducers. With the conclusion of these experiments, the accelerometers were shown to have highly variable results, especially for shear wave velocity, while the other methods yielded relatively consistent, reliable results as compared to published values. Finally, a new design for a triaxial setup that enables integrated measurements of compressional and shear velocities in soil over a wide stress range is presented as groundwork for the characterization of the complete stiffness matrix of BBC. en_US
dc.description.statementofresponsibility by Jana Marjanovic. en_US
dc.format.extent 189 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri en_US
dc.subject Civil and Environmental Engineering. en_US
dc.title The study of shear and longitudinal velocity measurements of sands and cohesive soils en_US
dc.type Thesis en_US S.M. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering. en_US
dc.identifier.oclc 813829933 en_US

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