基于工程包边法的膨胀土抗剪强度干湿循环效应试验研究

根据包边法施工中填芯重塑膨胀土和包边石灰改性膨胀土的实际工程状态,设计了反映其运营状态的干湿循环过程,对6次干湿循环前、后膨胀土的强度特性进行了较为系统地试验研究。结果表明,在压实度为90%⁹6%时,干湿循环前重塑膨胀土和石灰改性膨胀土慢剪强度及强度参数均随干密度单调增加,而干湿循环后其黏聚力c随干密度单调增加,干密度对内摩擦角φ的影响则明显变小;重塑膨胀土和石灰改性膨胀土干湿循环后的残余强度受干密度制约性不大,但干湿循环前、后重塑膨胀土和石灰改性膨胀土的残余强度参数存在差异,且干湿循环幅度对膨胀土强度参数也有一定的影响;在分析干湿循环前、后反复剪切试验结果及膨胀土边坡长期破坏机制的基础上,认为对于膨胀土路堤,在进行强度参数选取时宜适当考虑干湿循环及其幅度对于残余强度参数的影响;利用石灰改性膨胀土包边处理填筑膨胀土路基较为适宜。

Experimental research on shear strength of expansive soil under wetting-drying cycles based on wrapping method

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.