三峡库区青石-抱龙段顺层灰岩库岸坡变形破坏机理

三峡库区基岩顺层滑坡大多以砂/泥岩或泥/泥灰岩互层滑坡为主,力学机制以顺层滑移剪切为主。新近发现的青石-抱龙段顺层灰岩库岸,岸坡岩性以灰岩、白云岩为主。在21个顺向斜坡中9个斜坡存在岩层弯曲现象,高程分布在145~175m,且大量层面有擦痕,局部岩层强烈弯曲形成了类似逆断层的现象。这些变形破坏现象受控于重力作用下沿层面的滑移-弯曲力学机制。通过连续-非连续数值分析方法研究表明,在这一带岸坡中约200m的主动平直滑移段下滑力驱动了约30m的被动弯曲隆起段变形,被动弯曲隆起段位移地形变缓、岩层增厚。当前青石-抱龙一带顺层灰岩库岸岩层隆起和松动较小,处于滑移-弯曲变形的早期阶段,主要以累进性变形为主。建议对该段库岸进行专业监测,并开展进一步的调查研究工作。

Deformation mechanism of bedding limestone bank slope from Qingshi to Baolong,the Three Gorges Area

Bedrock of most of the bedding landslide in the Three Gorges Area is interbedding sandstone and mudstone,or interbedding mudstone and marl. The mechanical mechanism of the landslide is mainly bedding shear slip. Geological survey from in Qingshi to Baolong reveals that the lithology of the bank slope is mainly limestone and dolomite. At the elevation between 145 ~ 175 m,9 slopes in the 21 consequent slopes have the phenomenon of strata bending,and a large number of scratches were found at the bending surface. The deformation and failure phenomena are similar to the reverse faults in local strong bending strata. These deformation and failure phenomena are controlled by the mechanism of sliding and bending under gravity. The study of continuous-discontinuous numerical analysis indicates that there is an active straight slip section of about 200 m in the bank slope in this range,and its sliding force causes the deformation of the passive flexural uplift section of about 30 m. The topography of the passive bending uplift section is gentle and the strata are thickened. At present,the bank is in the early stage of sliding-bending deformation,which is mainly progressive deformation. Therefore,it is suggested that professional monitoring and further investigation of the reservoir bank should be c carried out.