Effects of Soaking and Cyclic Wet-dry Actions on Shear Strength of an Artificially Mixed Sand

Abstract

This study focuses on the effects of soaking action and wetting-drying cycles on the shear strength of a sandstone-mudstone mixture. This mixture is constantly used as a filler in earth structures along bank of harbor or in a large reservoir. Two-type direct shear tests in laboratory, Soaking Direct Shear Test (SDST) and Wetting-Drying Direct Shear Test (WDDST), were carried out. The experimental data indicate that the shear strength is reduced by the soaking action and wetting-drying cycles. While the period of soaking time (t) increased from 24 to 392 hours, the values of initial angle of shearing resistance (φ0) and reducing angle of shearing resistance (φd) reduced from 45.17° to 40.26° and from 19.68° to 12.28°, respectively, along logarithmic curves. With increment of the number of wetting-drying cycles (N) from 1 to 30, the values of φ0 and φd reduced from 40.99° to 38.84° and from 8.76° to 7.58°, respectively, along logarithmic curves. During the soaking action or wetting-drying cycles, the inevitably lessening of the stiffness of soil particle would happen, and hence the shear strength of mixture is decreased. With increment of t or N value, the rates of effects is instantly reducing.