暴雨型滑坡降水入渗机理分析

Analysis of rainfall infiltration mechanism of rainstorm landslide

暴雨能诱发大量的滑坡发生,在不同地区存在不同的临界降雨值,每当雨强大于该值时,滑坡就会大面积发生,这已经被多起滑坡事件证实。一般地,入渗理论认为,当雨强大于一定值时,入渗率是常量,过强的降水会转化为地表径流,这与雨强越大滑坡越易发生、群发性越强的观察结果不一致。在斜坡体上存在大量的裂隙,它们对降水入渗有着很大的贡献,应用有限单元法分别模拟了有裂隙和无裂隙时斜坡体内瞬态渗流场的变化,并用Bishop法对不同埋深滑动面的稳定性做了计算分析。模拟结果表明:考虑裂隙时的计算结果与宏观观察结果更一致,在评价降雨入渗对斜坡稳定性的影响时,一定要充分考虑裂隙的存在,只有雨强大于一个临界值时才会有充足的降水通过裂隙渗入到斜坡深部,裂隙的影响才显著地表现出来。

Rainstorm could induce a mass of landslides occurrence. There was a different critical rainfall value in different regions, while the rainfall intension was larger than the value, a lot of landslide would occur, thus had been proved by many happened facts. In general, the theory of rainfall infiltration was the recharge rate was a constant when the rainfall intension was larger than the certain critical vaiue, the more redundant rainfalls become the flow on the earth surface, it couldn＇t infiltrate into the earth, as was not consonant with the fact that the more precipitation could induce the more landslide. There were a lot of fissures in the slope which had enormously contributed to the rainfall infiltration. It was simulated by finite element method that changes of transient seepage field in the slope with fissures and without fissure, and the slope stability was calculated in different depths potential slip surface via the Bishop method. It was shown that the calculation result, considering the fissures, was more consistent with the macroscopically observed facts. The fissures existing in the slope should be considered enough when the slope stability about rainfall infiltration was evaluated. Only the rainfall intensity was larger than the certain critical value, the enough rainfallfall could infiltrate into slope body along the fissures, the effect of fissures on stability would be obvious.