岩门村滑坡高分辨率遥感调查与机制分析

HIGH RESOLUTION REMOTE SENSING SURVEY AND MECHANISM ANALYSIS FOR YANMEN VILLAGE LANDSLIDE

2007年7月7日,四川达县岩门村斜坡发生滑坡,造成直接经济损失约人民币1.5亿元。采用滑坡前后的高分辨率卫星影像及"数字滑坡"技术,获取滑坡地质环境及滑坡前后的道路、水塘、植被群位移及高程变化的定量信息,根据斜坡各部分变形特征,将其划分为主滑区、牵动滑区、强影响区及影响区4个部分,各自活动方式分别为快速推移+前缘砂土液化和面状流动,牵引(或后退)式滑移,受拉力发生拉张裂缝、错位和局部位移,以及受振动发生小规模的裂缝和错位。以DEM求得原地面以上的滑走及堆积方量分别为132.6×104和132.2×104m3;结合钻孔资料求得滑面以上滑坡规模为1.97×106m3。岩门村斜坡具备形成滑坡的岩性及坡体结构条件,但所临河谷狭窄,难以发育大型厚层滑坡,但有适宜的临空空间供局部浅层滑坡活动。长期强降雨是岩门村滑坡的主要触发因素。就斜坡整体而言,本次滑坡活动释放能量不充分,在连续降雨情况下局部可能再次发生浅层滑坡,但难以发生整体大规模滑移。

A landslide occurred on July 7th 2007 in Yanmen village of Daxian County, Sichuan Province, and it caused economic loss of about RMB 0.15 billion. The information of the geological environment of the Yanmen slope, the displacement of roads, pools and tree groups, and the elevation variety before and after the landslide occurrence had been captured using high resolution satellite image with digital landslide technique. Based on the deformation characteristics the slope is divided into 4 regions： main sliding region, retrogressive sliding region, intensive influence region and influence region; and their moving styles are considered as quick push＋sand soil liquefaction and flow in plane manner at the front part, retrogressive sliding, tension cracks, deformation and partial displacement caused by tension force, small cracks and deformation caused by land shake. With DEM, the volume of mass of sliding out and deposit from ground before landslide were estimated as 132.6×10^4 and 132.2×10^4 m^3 respectively; and combining with drilling data, the landslide volume from sliding surface is estimated as 1.97× 10^6 m^3. The lithology and geological structure conditions for Yanmen village slope are feasible for forming a landslide but it is difficult to form large-scale and thick ones since it faces a small and narrow valley which is suitable for developing partial and shallow landslides. Long-term and intensive rainfall was the main inducing factor for forming Yanmen village landslide. As for whole slope, the movement of landslide occurred on July 7th, 2007 had not release energy sufficiently, therefore, in conditions of continuous rainfall, landslides may occur in parts of the slope but it is hard to have the large-scale landslide of whole slope.