紫坪铺水利枢纽工程左岸坝前堆积体 变形破坏机制研究

 为准确把握紫坪铺水利枢纽工程左岸坝前堆积体在水库运行期间的稳定性动态，进行了工程地质条件和堆积体特征调研，结合堆积体的演化规律分析判断其当前处于缓速蠕变演化阶段，在水库运行条件下其变形破坏主控因素为库水作用效应和地震动力效应，并分析主控因素的作用机制，重点研究堆积体在水库运行期间的变形破坏机制。研究发现，堆积体在水库运行期间可能发生表层蠕滑变形和局部坍塌现象，且存在整体沿底部、整体沿腰部、局部沿底部和局部沿腰部4种可能的失稳模式。然后讨论边坡工程中常用的莫尔–库仑准则和广义米赛斯准则的优缺点，分析常用失稳判据的由来，并根据收敛判据提出了具体的实用判别指标。通过强度折减法确定了局部沿腰部失稳模式的滑动面位置和形状，结合极限平衡法进行上述4种失稳模式在不同工况下的稳定性分析。最后分析堆积体的变形破坏演化过程，表明在水库运行期间将首先发生灯盏坪前缘局部沿腰部失稳破坏，继而可能诱发堆积体整体失稳破坏，因此其治理重点应在于严格控制灯盏坪前缘坡体的稳定性。

RESEARCH ON DEFORMATION AND FAILURE MECHANISM OF THE TALUS SLOPE LOCATED AT LEFT RIVERBANK AHEAD OF THE DAM OF ZIPINGPU HYDRAULIC PROJECT

The stability of the talus slope，which is located at the left riverbank ahead of the dam of Zipingpu hydraulic project，is extraordinarily important during the reservoir operation. Based on field investigation，the geologic background and structure character of the talus slope have been fully analyzed and specified. It is judged that the talus slope is just in the stage of slow creep deformation currently by the evolutionary rule of the slope. The chief controlling stability factors are the reservoir water effect and the earthquake effect under the reservoir working condition. And the mechanism of the reservoir water and the earthquake action to the slope are also analyzed. The paper focuses on the deformation and failure mechanism of the talus slope. The phenomenon of superficial creep deformation and submerged failure would arise and there would be four failure patterns of the talus slope during the reservoir operation. The merits and defects of the yield criterion are discussed，which are Mohr-Coulomb yield criterion and generalized Mises yield criterion used extensively in slope engineering. And the instability criterion is comprehensively analyzed. The specific criterion indexes are put forward by the convergence criteria. And then the location and shape of the most unfavourable slide surfaces are determined by the theory of strength reduction，which are located at the front slope of Dengzhan plateau. The stability of four failure patterns of the talus slope is researched by limit equilibrium method under various work conditions. The research results indicate that the local failure of the front slope of Dengzhan plateau would happen firstly and then the global failure of the talus slope would induce under the reservoir water drawdown conditions. Main attention should be paid to the stability control of the front slope of Dengzhan plateau.