三峡库区黄土坡滑坡I号崩滑体成因

Formation Mechanism of No.1 Part Slide of Huangtupo Landslide in the Three Gorges Reservoir Area

黄土坡滑坡是三峡库区4个大型滑坡之一,因其典型性和重要性,"长江三峡库区地质灾害研究优势学科创新平台"在此建立了巴东野外大型综合试验场.野外试验场隧洞群揭露滑坡结构,有助于深入认识和研究黄土坡滑坡的地质结构特征和成因机制.通过试验隧洞开挖揭露黄土坡滑坡临江I号崩滑体特征发现:(1)临江I号崩滑体滑床基岩普遍发育层间剪切软弱夹层;(2)主隧洞与Ⅲ号支洞揭露滑体特征表明,滑体物质组成为棕红色泥岩、粉砂岩碎石土,灰色泥灰岩、灰岩碎石土,各类破碎岩层,滑体内潜水丰富,渗水量较大;(3)试验隧洞揭露滑带具有多层位顺层发育特征,平面范围与前人勘察成果较一致,厚度在不同剖面处存在较大差异;(4)深部钻孔监测资料显示,在土层与基岩面及层间剪切带均有蠕滑位移.分析得出:临江I号崩滑体是在重力和构造应力作用下顺多层软弱夹层、土层与基岩面发生蠕滑变形形成的,具有多层滑动面.

Huangtupo landslide is one of the four largest landslides in the Three Gorges Reservoir area, where the Badong field laboratory is built by Three Gorges Research Center for Geo-hazards, Ministry of Education because it is typical and signifi- cant. The geological structure characteristics and formation mechanism of Huangtupo landslide can be clarified by exposing slope structure through the test tunnel excavation. Up to now, the geological structure of No. 1 part slide exposed by the test tunnel excavation yield the following results： （1） In the bedrock of the No. 1 part slide, the incompetent interlayers develop widely. （2） The excavation of the main test tunnel and the No. 3 subsidiary test tunnel reveal that the displaced materials are composed of reddish brown mudstone and siltstone gravels, gray marlite and limestone gravels, and various crack strata. The ground water of the displaced materials is rich and the amount of water seepage is large. （3） The surfaces of rupture develop along the incompetent interlayers and the contacting surface between the stratum and the soil. The distribution of the surfaces of rupture in plane is very close to that obtained in previous studies. However, there exist some differences in the depth of the rupture surfaces. （4） The displacement monitoring data of deep boreholes show that there are creep displacements at the in- competent interlayers and the contacting surface between the stratum and the soil. Therefore, it can be concluded that the No. 1 part slide crept along the incompetent interlayers and the contacting surface between the stratum and the soil under the long- term influence of tectonism and gravity, and the No. 1 part slide has several surfaces of rupture.