降雨对库岸区边坡稳定性的影响研究

Study on the Influence of Rainfall on the Stability of Reservoir Bank Slope

库区修建高速公路有时因为地形条件等原因会无法避免把高速公路建在临湖地段,这就使得临湖路堤边坡会受到复杂水文条件的影响。水位的涨落会对边坡的稳定性产生重要的作用,很多临湖滑坡是发生在水位升降期间的,因此对此进行研究非常有必要。利用有限元软件迈达斯进行临湖区路堤边坡的模拟研究。结果表明,边坡水位的升降对边坡稳定性具有重要的作用。当水位上升时,动水压力的作用使安全系数增加;当水位稳定、土体接近饱和时,动水压力消失,边坡安全系数降低,最终由于基质吸力的消失而变得更加不稳定;当水位下降时,情况基本与上升时相反,安全系数先降低后升高,最终比水位下降前更高。只是在同样的水位升降下,边坡土体的排水时间比进水时间更长。水位上升和下降的速度也有一定的影响,变化更快导致动水压力更大,对边坡稳定性会更有利或不利;对于库岸区边坡,影响边坡稳定性因素主要是边坡的水位,坡面的降雨由于产生的动水压力较小,所以对边坡的作用是削弱了边坡的稳定性。这一点无论水位上升还是下降的情况下都是一样的。

The expressway built in the reservoir area is sometimes impossible to avoid the construction of expressway near the lake because of the terrain conditions.This is the slope of the embankment near the lake which will be affected by complex hydrological conditions.The fluctuation of water level plays an important role in the stability of the slope,and many landslides near the lake occur during the period of water level rise and fall,so it is very necessary to study on this.In this paper,the finite element software Midas is used to simulate the slope of the embankment near the lake.The results show that the rise and fall of the slope water level plays an important role in the stability of the slope.When the water level rises,the effect of hydrodynamic pressure increases the safety factor.When the water level is stable and the soil is close to saturation,the hydrodynamic pressure disappears and the safety factor of the slope decreases.Finally,the slope becomes more unstable due to the disappearance of matric suction.When the water level drops,the situation is basically opposite to that when the water level rises.The safety factor first decreases and then increases,and finally is higher than that before the water level drops.However,under the same water level rise and fall,the drainage time of the slope soil is longer than the inflow time.The speed of rising and falling water level also has a certain influence.The faster change will lead to the greater hydrodynamic pressure,which will be more favorable or unfavorable to the stability of the slope.For the slope in the reservoir bank area,the main factor affecting the stability of the slope is the slope water level.The rainfall on the slope weakens the stability of the slope due to the small hydrodynamic pressure generated by the slope.This is true whether the water level is rising or falling.