膨胀土边坡的失稳特征与稳定性分析

Instability characteristics and stability analysis of expansive soil slope

以湖北当阳某膨胀土边坡实体工程为依托,结合工程实际调研和现场测斜数据,观测上覆堆载和膨胀力作用下膨胀土边坡的失稳滑移位置及其形状特征,分析膨胀土边坡的滑动破坏特征及其致滑机制。结合膨胀土强度参数、膨胀力等物理力学指标,基于Bishop法、Janbu法等基本思想,推导上覆堆载和膨胀力作用下的膨胀土边坡稳定性计算公式。基于工程实例,分析上覆堆载、位置以及膨胀力对膨胀土边坡稳定性的影响。研究结果表明:在上覆堆载和水分入渗的作用下,当阳地区膨胀土边坡呈整体滑移破坏,呈现坡体后缘开裂、前缘圆弧状滑出的特征;堆载荷载增大、堆载距坡肩间距减小和膨胀力增加导致膨胀土边坡稳定系数持续下降;当膨胀力较小时,由改进的Janbu法和Bishop法得到的膨胀土边坡稳定系数接近;随着膨胀力增大,这2种方法所得的膨胀土边坡稳定系数差异增大。

According to a typical project of expansive soil slope in Dangyang,Hubei Province,the position and the shape of the potential sliding surface for the overall instability of expansive soil slope subjected to the function of overburden load and swelling pressure were observed based on engineering investigation and on-site inclination data.The sliding failure characteristics and sliding mechanism of expansive soil slope were analyzed.Combining the strength parameters of expansive soil,the swelling pressure and other physical and mechanical indexes,the formula for calculating the stability of expansive soil slope under the function of overburden load and swelling pressure was deduced based on the basic ideas of Bishop method and Janbu method.The influence of overburden load,the position of overburden load,and the swelling pressure on the stability of expansive soil slope was analyzed according to an engineering example.The results show that the expansive soil slope in Dangyang area shows overall slippage failure model subjected to the function of the overburden load and water infiltration.There are cracks at the rear edge of the slope,and the soil mass slides out of the front edge in an arc shape.A continuous decrease of the stability coefficient of expansive soil slope is induced by the increase of overburden load,the decrease of overburden load spacing,and the increase of the swelling pressure.When the swelling pressure is small,the stability coefficient of expansive soil slope obtained by the improved Janbu method and Bishop method are close.As the swelling pressure increases,the difference in the stability cofficient of expansive soil slope obtained by the two methods increases.