STRENGTH OF SANDY CLAYS

Abstract

Foundation has paramount importance in all Civil Engineering structures like building, bridge, highway, canal, dam etc. The performance of foundation primarily depends upon the characteristics of soils, on which it is founded. Therefore, thorough knowledge of strength-related properties of soils including the effects of percentage of different constituents, moisture content, vibration etc. are most essential, so that the designer can incoporate these in the design of foundation, if there is any possibility of variation during the life-time of the structure. Most of the literature available in connection with strength characteristics of soils are on fine grained and coarse grained soils, while soil occurring in nature are usually mixture of two i.e. sand and clay. In sandy clay, the percentage of sand has significant effect on its strength, because the basic properties of both constituents are different. In case of sand, the interparticle forces are due to friction and the effect of water is limited. But in case of clay the interparticle forces are due to cohesion and the effect of water content varies to a great extent. In this dissertation work, the effects of variation in percentage of sand on the strength properties of sandy clay have been studied under different degree of saturation. In this study, tests have been carried out on sandy clays consisting of 90%, 80%, 70%, 60% and 50% clay and 10%, 20%, 30%, 40% and 50% sand respectively. In each case, tests are conducted at 0%, 25%, 50%, 75%, and 100% degree of saturation to determine the unconfined compressive strength, shear strength parameters (Cu,& VDU) and vane shear strength. On the basis of data obtained from the laboratory testing programme, carried out on remoulded samples, plots have been drawn showing the effects of variation in percentage of sand and degree of saturtion on unconfined compressive strength, direct shear strength and vane shear strength. Fin'ally, the results have been concluded._