水位骤变触发库岸堆积层滑坡的物理模型试验及机理分析

库区水位骤变容易引起库岸边坡堆积层滑坡，而水库库岸滑坡往往会直接造成水工建筑物的损毁、减少有效库容，因此深入研究其诱发机理和变形破坏模式具有重要意义。本试验在模型箱内进行，其净空尺寸为100cm60cm60cm（长宽高），内设不透水底板模拟基岩体，通过水闸可以实现水位的骤降。在不透水底板上填筑有厚度约为20cm的堆积层，并在堆积层内部埋设传感器，用于测量土压力和孔隙水压力的变化过程，并在试验全过程中用摄像机记录了滑坡的变形位移情况。试验结果表明：在水位上升过程中堆积层表面会形成张拉裂缝，边坡前缘涉水区域发生局部破坏，主要是由于库水入渗后，水对岩土体会造成抗剪强度弱化； 水位骤降时，堆积层会沿着基岩面发生整体下滑，滞留在土体中的孔隙水压引起的渗流力是导致该滑坡发生的主要因素； 由于水库库岸堆积层滑坡是在渗流力牵引作用下发生，故滑坡失稳模式一般为牵引式滑坡。

PHYSICAL MODELING TEST AND MECHANISM ANALYSIS FOR RESERVOIR ACCUMULATION LANDSLIDE TRIGGERED BY RAPID FLUCTUATE OF WATER LEVEL

The rapid fluctuation of water level of reservoir is liable to cause accumulation landslide, and the failure of reservoir slope often causes damage to hydraulic structures and reduces storage capacity. So that, study its mechanism and the deformation failure mode is important. The test was performed in a rectangular box with the length of 100cm, the width of 60cm and the height of 60cm. A plastic board was set up in the test box, which was used to simulate the bedrock impervious to water. A sluice was developed to implement the simulation of the rapid drawdown of water level. About 20cm thick accumulation was filled on the plastic board. The sensors were buried in the accumulation and used for measuring earth pressure and pore water pressure during rapid fluctuation of water level. The deformation of slope was recorded during the test process by digital camera. The experimental results indicate that the tensile cracks initiate on the surface of accumulation, and a local failure of slope toe have happened in the raising of water level, as the water decreases shear strength of soil; in the process of water level drawdown, the accumulation slips along rock base, and the residual pore-water pressure is a major factor in landslide. The failure mode of reservoir slope is pull-type, due to the landslide is triggered by seepage force.