蓄水及降雨条件下库岸边坡变形机理研究

An Analysis on the Deformation Mechanism of Slope in the Process of Reservoir and Rainfall

库岸边坡变形与水位波动及降雨等有着密不可分的关系。水库蓄水及降雨都会引起地下水位抬升,局部坡体由不饱和状态转为饱和状态。浸水的岩土体和地下水相互作用,致使坡体力学参数弱化而稳定性降低;另外地下水位波动会施加动静水压力在坡体上,这也会导致坡体稳定性下降。为了研究在蓄水及降雨条件下边坡的变形机理及影响稳定性的主导因素,以雅砻江某电站库岸边坡为例,利用蓄水过程第一手监测资料及地质现象对其变形机理进行分析,结合传递系数法对四种工况进行计算。分析认为：蓄水过程库水位的变化与坡体变形规律有着一定的相关性,结合稳定性计算可知库水的陡升对坡体变形起主导作用。建议蓄水过程可以分阶段渐进式进行来消除这种影响;坡体在蓄水过程中,有着典型的蠕变规律：库水快速上升后,坡体滞后1-2月也开始加速变形;随着后期库水波动基本保持平稳,坡体变形也随之减速并最终趋于稳定;综合研究区地质条件及监测分析,判定滑坡变形机制为蠕滑-拉裂式。然而整个蓄水过程边坡变形都在允许范围内,不会发生失稳。

The deformation of reservoir slopes has the close relation with water fluctuation and rainfall, etc. Reservoir and rain can cause groundwater level uplifting, a partial slope can turn from unsaturated state into saturat- ed state. Soil masses soaked has interaction with groundwater. That weaken mechanical parameters of slope and reduce stability of slope. Besides, groundwater fluctuation put hydrodynamic pressure on slope to reduce stability of slope. In order to study deformation mechanism and stability dominant factor of slope under the reservoir and rain conditions, a reservoir slope of large hydro-power station on Yalong River was discussed here. Through used firsthand monitoring data and geologic phenomena in the region to analysis the deformation mechanism of slopes, transport coefficient method was combined to compute for four conditions. The analysis suggested there was significant relationship between water levels and laws of slope deformation during water filling, upturn of water played a dominant role in the slope deformation based on the calculation of its stability. There is a suggestion the reservoir is impounded gradually in stages to eliminate the influence. Slope deformation had a typical creep laws during water filling： slope had an accelerated deformation with 1 - 2 months＇lag when water raised rapidly. Slope had an decelerated deformation and tended to be stable finally, when water was little changed and stable. Based on the geological conditions and monitoring in the researched region, analysis suggests that the slope deformation mechanism is of creep sliding-tension cracking. However, in the process its deformation should be controlled within tolerances and was still in a stable state.