古水水电站工程区域堆积体边坡工程地质分析

ENGINEERING GEOLOGY ANALYSIS OF COLLUVIAL SLOPE AT HYDROPOWER STATION PROJECT IN GUSHUI

西南地区水电工程中堆积体边坡的稳定性问题研究对水电工程建设极为重要。堆积体边坡研究中比较关键的问题包括:堆积体的历史成因、不同条件下的力学参数取值和稳定性分析。本文通过对古水水电站坝址区域内下覆为板岩、上覆为堆积体的工程地质条件进行了相关分析,得到了该区域上覆堆积体和下覆板岩倾倒变形的历史演化过程:在冰水的携带作用下,边坡顶部的岩土体逐步向下迁移而形成堆积体,并且表现出明显的层状效应;板状岩体在构造运动、河谷下切和风化卸荷等共同作用下,加之上覆堆积体重量的不断增加,从而发生折断并导致倾倒变形。在对冰水堆积体物理力学特性分析的基础上,结合现场的工程地质调查,得到了区域内堆积体边坡的变形破坏模式表现为顺软弱面整体滑动破坏和局部圆弧型滑动。

Abstract Stability of slopes comprising colluvium is very important to the hydropower station construction in the southeast of China especially. The key tasks are to find the answers for the questions： the reasons of accumulation formation, mechanical parameter values and slope stability under different conditions. This paper analyzes the typi- cal engineering geology condition of the dam site zone of a hydropower station at Gushui. The lower zone is slate and the upper is colluvium. The paper examines the history of the engineering geology condition at this region. It further examines the formation of the colluvium at the upper zone and obtains the topping deformation of slate at the lower zone. Due to schlep effect, the colluvium was formed. The rock - soil materials on the top of slope move down in schlep effect of outwash. The colluvium has a clear layering structure. The slate experiences a continuous increase in under the effect of tectonic movement, incised valley and weathering unloading and also the weight of upper colluvium. Breaking of the slate is happened and lead to topping deformation. Based on the analysis of physi- cal and mechanical characteristics of the colluvium, and combined with the survey of engineering geology condition,the mechanism of failure and deformation of the colluvium slope is obtained. Its contains the wholly slide failure along the weakly layer and the locally arc slide failure.