龙门山断裂北川断裂带滑坡与构造活动关系研究

Relationship between landslides and tectonic activities in Beichuan fault zone of Longmenshan fault

北川断裂带位于龙门山中央断裂带中部,新、老滑坡较为发育,构造活动是影响区内滑坡发生的主导因素。采用文献记载、现场调研等方法,分析了构造对滑坡灾害的影响,结果表明:①构造横向挤压、不均匀抬升对地表岩体的完整性进行改造,使得不同构造部位、斜坡部位岩体存在结构差异,进而控制滑坡在空间上的发育规律,同时,细部构造结构面在空间上的产出关系构成了滑坡发生的初始边界条件;②作为构造活动的剧烈外部表现,地震动荷载直接诱发滑坡的同时造成斜坡岩体的松动;③"5·12"震后,区域构造应力方向发生近90°的偏转,进一步加剧了松动岩体的变形与破坏,震后应力偏转是影响区域斜坡稳定的最主要内动力因素。

The Beichuan fault zone is located in the middle part of the central Longmenshan fault zone,Sichuan,where the new and old landslides develop well and the tectonic activity is the dominant factor affecting landslides in the area. The influence of tectonic activity on landslide disaster is analyzed by means of documentary record,field investigation,etc. The results show that: ① The integrality of the surface rock mass was reformed by lateral compression and uneven elevation of the structure,which caused structural differences of the rock masses located at different structural positions or slopes and further controlled the spatial development law of landslide. At the same time,the spatial exposure relations of the detailed structural plane formed the initial boundary conditions for the occurrence of landslide. ② As a violent external representation of tectonic activity,seismic dynamic load induced landslide directly and loosed the rock mass at the same time. ③ After ' 5. 12' earthquake,the direction of regional tectonic stress was nearly 90 degrees deflection,aggravating the deformation and failure of loosed rock mass. The post-earthquake stress deflection was the main internal dynamic factor affecting regional slope stability。