关键词: 膨胀土, 包边法, 干湿循环, 残余强度

Abstract: Wrapping method is a effective method to expansive subgrade. Based on the condition of wrapping method, a wetting-drying cycle path was designed for the expansive soil and lime-treated expansive soil. The strength properties were studied and discussed for the samples experiencing 6 wetting-drying cycles with the systematic research of the shear strength before and after wetting-drying cycles. The results show that the shear strength increases with the increasing dry density for remolded and lime-treated expansive soils in the range of compactness between 90% and 96%. The variation of shear strength parameters are different for the soil samples before and after wetting-drying cycles. The cohesion after wetting-drying cycles increases with the increasing of dry density; but the influence on internal friction angle is small. The dry density restricts residual strength little for remolded and lime-treated expansive soils after wetting-drying cycles. The residual strength parameters of expansive soils are different for the samples before and after wetting-drying cycles; and it is larger before wetting-drying cycles. The strength parameters including peak strength parameters and residual strength parameters are influenced by the range of wetting-drying cycles. Based on the influence of wetting-drying cycles and repeated shearing on strength parameters, it is suggested that the difference of residual strength parameters before and after wetting-drying cycles and its range can be considered to analyze the safety factor of expansive clay slope. And lime-treated expansive soil is fit for wrapping in the expansive soil subgrade.

Key words: expansive soils, wrapping method, wetting-drying cycle, residual strength