陕西省安康市洪山镇地质特征及其对向家滑坡的控制作用

Hongshan's Geological Features and the Analysis of Control Action on Xiangjia Landslide,Ankang in Shaanxi Province

向家滑坡形成于南秦岭北大巴山构造带紫阳-平利滑脱逆冲推覆带。该滑坡位于局部南东倾向韧性剪切带之中。韧性剪切带以压扭性和张扭性为特征,经历了多期(次)活动,形成了二长岩脉和多期(次)石英脉的生成,韧性剪切带后期转化为脆性断层。因此,洪山镇向家滑坡的发生、发展与韧性剪切带和寒武系多期变形密切相关,高剪切应变带主要表现为岩石发生了强烈塑性变形,形成塑性流动构造;岩脉侵位,致使局部构造应力场中主应力方位σ1近于垂直,加上绢云母石英片糜岩中片理构造非常发育,绢云母和石英两类岩石力学性质差别很大的矿物均沿片理面集中分布,在雨水侵蚀过程中极易产生滑动而生成滑坡。

Xiangjia landslide is located at the Ziyang-Pingli detachment thrust belt,which belongs to South Qinling-North Dabashan tectonic zone.The landslide is imbricated into a southeast-vergent ductile shear zone which has experienced multi-time activity.The ductile shear zone has the characteristics of both twist-compression and twist-tension deformation,together with the appearance of Monzonlite dykes and quartz veins,finally turns into the brittle faults.Therefore,it is clear that the occurrence,development of Xiangjia landslide has the important relationships with regional ductile shear zone and Cambrian polyphase deformation.The characteristics take as follows： primarily,the rock has produced strong plastic deformation and formed plastic flow structure at the high shear strain zone.Moreover,the diapir emplacement makes the principal strain direction sigma 1 nearly vertical in a portion of the tectonic stress field.In addition,there are many schistosities extremely developing in the sericite-quartz phylonite;and the two minerals,mica and quartz,have the obviously distinctive mechanical properties,also distribute along the schistosity plane on a large scale.On top of this,sericite-quartz phylonite are inclined to slide in the rain erosion,given to the weather factor,and usually generate the larger landslide.