高山峡谷区某顺层边坡地质特征及稳定性研究

Study on Geological Characteristics and Stability of A Bedding Slope in Alpine Canyon Area

某特大桥左岸支沟侧为顺层边坡,其稳定性是大桥建设的基础。采用地质调绘、钻探、硐探、钻孔全景摄像等手段查清边坡地质特征,通过工程地质和赤平投影分析初步判定边坡破坏形式,利用FLAC、UDEC、3DEC软件模拟分析边坡岩体的变形破坏规律,采用极限平衡法计算分析边坡、危岩体及堆积体的稳定性。研究结果表明:二级斜坡、三级斜坡分为基岩裸露区和深厚堆积体区2个区段,潜在破坏模式为平面滑动破坏及楔形滑动破坏;边坡整体处于稳定状态,强降雨+地震工况下,高为15,20 m的楔形体可能沿坡面及陡崖方向发生滑动破坏,二级斜坡顶部危岩体可能发生失稳、底部堆积体处于欠稳定状态;建议基础埋置于稳定的完整岩体一定深度,强化桥基岩体和锚碇围岩的加固处理,并加强抗震和边坡防护设计。

The side of the branch ditch on the left bank of a bridge is a bedding slope,and its stability is fundamental to the bridge construction.Geological mapping,drilling,cave exploration and digital borehole panoramic image are used to identify the slope geological characteristics.Engineering geology analysis and stereographic projection analysis are conducted to preliminarily determine the failure form.FLAC,UDEC and 3DEC software are used to simulate and analyze the deformation and failure law of slope rock mass.The limit equilibrium method is employed to calculate and analyze the stability of slope,dangerous rock mass and accumulation body.The results show that the secondary and tertiary slopes are divided into two sections:exposed bedrock area and deep accumulation area.The potential failure modes of the slope are plane sliding failure and wedge sliding failure.The slope as a whole is stable.Under the conditions of heavy rainfall and earthquake,the wedges of 15 m and 20 m in height tend to slide along the slope and scarp direction,the dangerous rock mass at the top of the secondary slope may be unstable and the accumulation at the bottom is in an unstable state.It is suggested that the foundation should be buried in a certain depth of the stable complete rock mass.The reinforcement of rock mass,the seismic and slope protection design should be strengthened.