Influence of swell on shear strength of expansive soils

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2016

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Deliktaş, Ceren

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Behavior of swelling soils is thoroughly investigated since they cause significant hazard to structures all around the world, especially in the regions with climate of arid or semi-arid. These types of soils expand upon wetting and shrink when water is removed. Existence of water significantly alters the shear strength of swelling soils. Therefore, the objective of this study is to examine the influence of swell on the shear strength of expansive soils. For the first series of tests, an artificial expansive soil was prepared in the laboratory by mixing 15% bentonite and 85% kaolinite. Grain size distribution, specific gravity, Atterberg limits and dry density versus moisture content curve were determined. Then, to obtain swell percent and rate of swell, swell tests were conducted in special molds and unconfined compression tests were made. For the first series of tests, soil samples were sheared without allowing expansion to take place. This test was considered as the reference test. Then, specimens were sheared after they were allowed to swell in specially designed molds until vertical swell stopped, which were referred to 100% swell. In the mid-steps, shear strength was obtained when soil sample reached to 10%, 15%, 20%, 25%, 50% and 75% of ultimate vertical swell. These eight swell and shear tests were repeated for three expansive Ankara clays having different swelling potentials since natural soil samples could be found just in Ankara. As the result of shearing tests, it was seen that when the specimen reached to ultimate swell, shear strength was reduced to approximately 90% of its initial value. Free swell index test and methylene blue test were performed to estimate the swelling potential. Besides, tests showed that a frictional stress equal to about 17-25% of swell pressure developed between the mold and specimen.

Subject Keywords

Swelling soils., Soil mechanics., Shear strength of soils

URI

http://etd.lib.metu.edu.tr/upload/12619914/index.pdf
https://hdl.handle.net/11511/25592

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

C. Deliktaş, “Influence of swell on shear strength of expansive soils,” M.S. - Master of Science, Middle East Technical University, 2016.