高速公路滑坡稳定性评价及其治理模拟

STABILITY EVALUATION AND TREATMENT SIMULATION OF AN EXPRESSWAY LANDSLIDE

对一高速公路由于路基开挖引起的滑坡进行现场考察和工程地质勘察的基础上,详细分析了该滑坡的工程地质条件及其变形特征,认为该滑坡系路基切方致使坡体阻滑力降低,并形成滑动变形的临空面,导致坡体沿板溪群强风化硅化砂岩顶部与上伏震旦系江口组全强风化硅化砂质板岩不整合接触部位产生滑动。通过FLAC3D对滑坡稳定性的数值模拟,证明该滑坡是由于滑带强度低和开挖坡脚造成的,提出先压脚支护再继续开挖的施工方案。采用基于强度折减法和FLAC3D中的桩结构单元,对不同开挖深度及抗滑桩支护后开挖到设计路基时的安全系数进行了计算。计算结果表明,支护后开挖到设计路基的安全系数是1.33,可满足工程安全的需要。

Based on the engineering geological exploration and site investigation of a landslide site induced by roadbed excavation on an expressway, the engineering geological conditions and the deformation characteristics of the landslide are described. It is concluded that the landslide is caused by excavation of the roadbed to decrease sliding resistance and to form a sliding air-face, resulting in the slope sliding along the weak interlayer between the overlying completely and intensely weathered siliceous sandy slate of the Jiangkou Group belonging to the Sinian System and the underlying intensely weathered siliceous sandstone of the Banxi Group. The numerical modeling results of stability indicate that the landslide is caused by low shear strength of the sliding plane and toe excavation, and that the resisting force should be applied to the toe of the slope by backfilling, and that stabilization measures should then be taken before continuing excavation of the roadbed. The shear strength reduction method is employed to compute the variations of the factors of safety with the depth of excavation before and after the slope is supported by anti-slide piles. It is indicated that the factor of safety of slope after stabilization is 1.33 when it is excavated to the designing roadbed; and it can meet the safe demand of the engineering.