板梁状滑坡形成条件、成因机制与防治措施

 以发生于四川省南江县兴马中学滑坡和大河中学滑坡这2个新老滑坡为典型案例，通过详细调查和分析解剖，提出一种新的平推式滑坡类型——板梁状滑坡。板梁状滑坡平面上呈扁长矩形，纵向长度远小于横向宽，剖面上呈薄板状。其主要发生于由近水平巨厚层砂岩和薄层泥岩构成的斜坡陡崖附近，坡内存在一组平行于坡面的长大陡倾结构面。在强降雨条件下，平行于坡面的张裂缝被快速充水至某一临界高度后，强大的静水压力将外侧岩体整体平推出去，形成平推式滑坡，而后随着裂缝内水头的骤降，滑体很快会自行止动。在较系统地研究并查明形成板梁状滑坡必须具备的岩性条件、坡体结构条件、裂缝储水条件以及强降雨触发条件的基础上，针对板梁状滑坡的后续变形破坏模式，提出加强截排水，消除在裂缝内形成高水头的条件；在板梁外侧根部采取短桩或抗滑键阻止板梁进一步向外滑动；顶部采用连梁或锚索约束其倾倒变形等有针对性的工程治理措施。

FORMATION CONDITION,GENETIC MECHANISM AND TREATMENT MEASURES OF PLATE-SHAPED LANDSLIDE

Taking two new and old landslides,located at Xingma Middle School and Dahe Middle School in Nanjiang County,Sichuan Province,as topical cases,a new translational landslide named plate-shaped landslide is presented analyzed through these two cases. The characteristics of such landslides are thin rectangular plate,with the length of the longitudinal axis of the plane shorter than the lateral axis. And it is like a thin plate in section. The main geological setting of this kind of landslide is thick sandstone rock bed inter-bedded with a mudstone rock bed on the bottom,in which there is a long discontinuity developed inside the slope which parallels to the slope angle. The discontinuity will develop into a tension crack when the heavy rainfall occurs and it will be infilled with water quickly till the water table reaches to a certain critical level. The hydrostatic pressure will push the block on the free side out and such movement will stop when the water table in the crack drops with the crack being large enough. A systematic study of the lithology background,tension crack contain water as well as the rainfall triggering factor condition is carried out. Based on the study,in light of the deformation pattern of the plate-shaped landslide,some measures to treat the landslide are provided,which include operating the drainage project to make sure the water can be drained in the crack,setting a short pile or anti-sliding block outside in the toe of slope to prevent the sliding movement,and setting beams or anchorage cables between the blocks on the top of slope to control the deformation which is caused by tension cracks.