金沙江永善—水富段滑坡分布规律及其形成模式

Distribution law and forming mode of landslides along Yongshan-Shuifu section of Jinsha River

为了评估金沙江向家坝水库(永善—水富)蓄水后岸坡稳定性,同时为水库运营期地质灾害监测预警提供参考资料,以地质图、地形图、正射航空影像和SPOT-5商用卫星影像为基础资料,利用GIS平台,结合蓄水前现场调查和遥感解译方法建立滑坡数据库,利用统计学方法分析滑坡空间分布与岸坡结构、地层的关系,最后归纳了滑坡的四种形成模式。获得以下结果:(1)滑坡主要发育于新市镇以下侏罗系地层,新市镇以上滑坡分布受猰子坝断层控制;(2)缓倾外顺向层状岸坡(Ⅲ1)滑坡数量分布密度最大,斜向层状岸坡(Ⅴ)滑坡数量分布密度最小;(3)侏罗系自流井组(J2z)的滑坡点密度最大,二叠系乐平组(P2l)的滑坡面密度最大;(4)库区已有滑坡形成模式可归纳为四种:(1)倾坡外层状岩体岸坡(Ⅲ2)的切层滑动;(2)缓倾坡外层状岩体岸坡(Ⅲ1)的顺层滑动;(3)缓倾坡内层状岩体岸坡(Ⅳ1)的弧形滑动;(4)崩坡积、冲积松散层顺下伏基覆界面滑动。在向家坝水库蓄水期及运营期,应重点监测新市镇以下岸坡,尤其是缓倾外顺向层状岸坡(Ⅲ1)。

In order to evaluate the stability of the bank-slope of Xiangjiaba Reservoir on Jinshajiang River（the section from Yongshan to Shuifu） after impounding and simultaneously provide reference data for the monitoring and early warning of geologic hazards during the operation period of the reservoir,a landslide database is established with GIS platform in combination with both the site investigation before the impounding and the method of remote sensing interpretation on the basis of the relevant geological map,topographical map,aerial orthophotos and commercial satellite image of SPOT-5,and then the relationship between the spatial distribution of landslide and the bank-slope structure as well as the strata therein are analyzed with the statistical method; from which four forming modes of the landslide are summarized,i.e.（1） the landslides mainly develop from the Jurassic strata located at the downstream of Xinshi Town,while the landslide distributed at the upstream of the town are controlled by Yaziba fault;（2） the distributed density of the landslide number is the maximum at the gently dipping outer stratified consequent bank slope（Ⅲ1）,while the distributed density of the landslide number is the minimum at the inclined stratified bank slope（V）;（3） the density of the landslide point of Jurassic artesian well group（J2z） is the maximum,while the landslide plane density of the Permian Leping group（P2l） is the maximum;（4） the forming mode of the existed landslides in the reservoir area can be sortedintothe following four kinds：（1）the cutting-bed sliding of dipping outer stratified rock bank slope（Ⅲ2）;（2）the consequent sliding of gently dipping outer stratified consequent bank slope（III3）;（3）the circular sliding of gently dipping inner stratified consequent bank slope（IV） and（4）the underlying interface sliding along the colluvium or deluvium loose layer.During the both the impounding period and the operation period,the bank-slope located at downstream of Xinshi Town,especially,the gently dipping outer stratified consequent bank slope（Ⅲ1） must be emphatically monitored.