考虑软弱基座风化效应的望霞危岩崩塌机制分析

Collapse mechanism of Wangxia dangerous rock mass considering weathering effect of underlying soft rock

三峡库区巫山县望霞危岩属上硬下软的软弱基座型边坡。软弱基座为页岩,抗风化性弱,易形成一定深度的低强度强风化带,甚至出现凹腔。软弱基座的压缩变形,是造成危岩压缩-滑塌失稳的主要原因。首先对望霞危岩工程地质条件及变形破坏特征进行分析,然后采用离散元UDEC模拟研究了软弱基座风化深度对危岩变形破坏过程及机制的影响规律。研究发现:通过考虑软弱基座的风化效应能较好地再现危岩的失稳过程。根据风化深度及危岩变形破坏演化,将危岩变形失稳过程分为稳定、累积损伤、座落及折断四个阶段。

Wangxia dangerous rock mass,at Wushan County in Three Gorges Reservoir area,consists of a soft shale foundation and hard upper rock mass.The shale is very weak in weathering resistance and easy to form strong weathered zone in a certain depth and even concave cavities.The compression deformation of the soft foundation is the main cause inducing compression-collapse of the rock mass.In this paper,the engineering geological conditions and failure characteristics of the dangerous rock mass are analyzed,and then the influences of the weathering depth of the soft foundation on the deformation and failure process and mechanism of the rock mass are studied by the discrete element method(UDEC).It is found that the failure process of the dangerous rock mass can be well simulated by considering the weathering effect of the underlying soft rock.According to the weathered depth and the failure evolution of the dangerous rock mass,the deformation process of dangerous rock mass is divided into four stages,stability,cumulative damage,downward dislocation and break off.