LABORATORY RESEARCH ON EFFECT OF FREEZE-THAW CYCLES TO SHEAR STRENGTH OF WEATHERED SAND IMPROVED WITH EXPANSIVE SOIL

This paper investigates the qualitative and quantitative relationships among shear strength of weathered sand improved with expansive soil, weathered sand content and cycle times of freeze-thaw tests. The expansive soil is added with weathered sand with the percentages of 0, 10%, 20%, 30%, 40%, 50%,respectively. The shear strength test is done using direct shear apparatus on the samples after 0, 1, 3, 6, 9, 12 cycles of freezing and thawing. Test results show that as the cycles of freeze-thaw increases, the shear indexes and the shear strength of weathered sand improved expansive soil first increase and then decrease and gradually reach stable after several times of freeze-thaw cycles for samples with the same sand ratio. The relationship between cohesive force and freeze-thaw cycles can be expressed in logarithmic function. As the mixed sand ratio increases, the cohesion decrease but the internal frictional angle increases for samples with the same cycles of freeze and thaw.