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Abstract In order to study the influence of freezing-thawing cycles on the yielding and strength properties of silty sand from Qinghai—Tibet，the consolidated drained triaxial shear tests under different confining pressures and freezing-thawing cycles were conducted. The freezing temperature was chosen to be －5 ℃ during freezing- thawing cycles. It was found that the silty sand exhibited shear contraction and strain hardening during shearing. The types of volumetric curves and stress-strain curves were not changed after freezing-thawing cycles. The volumetric yield surface of unfrozen silty sand was expressed with an elliptic curve，while the yield surface for shearing was represented with a linear function passing the origin. The shapes of both volumetric yield surface and shear yield surface were not changed after freezing-thawing cycles. Both the volumetric yield function and the shear yield function were expressed as the power function of the plastic strain and numbers of freezing-thawing cycles. The shear strength of silty sand increased with the increasing of the normal stress，but decreased and then rised with increasing the number of freezing-thawing cycles. The cohesion of the silty sand was changed from 4.82 kPa to 2.07 kPa and the angle of internal friction was varied from 27.11°to 22.93°after freezing-thawing cycles. The linear Mohr-Coulomb criterion was adopted to describe the strength properties according to the strength variation of silty sand to the normal stress under freezing-thawing cycles.
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2015, Vol. 34 
