开挖膨胀土边坡坍滑的演化规律

Landslide Evolution Regularity of Excavated Expansive Soil Slope

膨胀土路堑开挖一段时间后边坡坍滑是路基施工中常见现象且与坡高、坡率无直接联系。为探求其变形破坏演化过程以便实施有效工程处治,采用FLAC对广西百隆路百色膨胀土堑坡开挖过程进行模拟,获得新开挖边坡的位移、应力、应变变化规律;通过强度折减法计算得到的安全系数随挖深增大而减小,但此时边坡是稳定的。此外采用FLAC热力学模块模拟边坡大气影响深度内的湿度场,再次分析获得经历干湿循环作用后其相应的位移、应力、应变变化规律,即边坡的失稳过程。对比工程实体修建时的现场观察与数值分析结果,发现两者基本吻合,由此总结并提出开挖膨胀土堑坡坍滑的4阶段变化规律及合理实施柔性支护的建议。

The sliding of expansive soil cut slope after excavation for a period of time is a common appearance during construction of expansive soil subgrade. This sliding is not directly related to the height and ratio of slope. In order to find out the evolution of its deformation and failure to implement effective engineering treatment, the FLAC is used to simulate the excavation process of Baise expansive soil cut slope of Bailong expressway in Guangxi and obtain its regularities of displacement, stress and strain. The safety factor of cut slope calculated by strength reduction method reduces with the increase of slope depth, but it is still stable after the complication of excavation. In addition, the thermodynamics module of FLAC is used to simulate the humidity field of atmospheric effect on depth of expansive soil slope, and get the regularities （damage） of the variability of the displacement, stress and strain of cut slope after wetting and drying cycles. The numerical simulation result is basically in accordance with the field observation result during construction of the cut slope. Therefore, the four-stage evolution regularity of sliding of excavated expansive soil cut slope is summarized and presented, and the technology of flexible supporting is reasonably proposed.