“下软上硬”二元结构型反倾边坡倾倒变形演化机理研究

Study on Toppling Deformation Evolution Mechanism of Anti-Dip Slope with‘Lower Soft and Upper Hard'Dualistic Structure

针对某水电站导流洞进口边坡开挖过程中出现的顺层面张裂缝问题,采用工程地质分析、数值模拟相结合的方法,定性、定量分析裂缝产生机理及开挖边坡稳定性。研究结果表明,进口边坡本质上是一个"下软上硬"的二元结构,作为边坡基座的Pt2-12y具有极薄层的岩体结构特征,开挖卸荷后呈现了较强的弯曲式倾倒变形;边坡潜在失稳区域集中在前缘Pt2-12y岩层内,其变形破坏模式由倾倒-拉裂为主转变为滑移-拉裂;从安全系数计算结果及倾倒变形体的一般破坏特征来看,当前条件下开挖边坡整体稳定是有保障的。

Aiming at the crack problem of the diversion tunnel inlet slope on the left bank of a certain hydropower plant during the excavation process,combination of engineering geological analysis and numerical simulation were used to analyze the crack mechanism and excavated slope stability.The results indicate that the inlet slope is composed of two parts‘the upper hard part and the lower soft part'.The rock mass structure at the basement of slope is observed to be very thin layered rock mass and shows remarkable bending induced toppling and falling deformation characteristics.During the evolution process of the toppling and falling deformation,a sliding surface develops gradually within the thin layered rock mass and finally penetrates through the basement area of the slope,thus causing instability of the whole slope and triggering the failure of the upper area of the slope.The safety factor of the slope is calculated.Based on the results,the toppling deformation of the slope and its instability approaching process have long-term variation characteristics.The inlet slope is currently stable under given conditions.