库水位下降和降雨对重庆万州下坪滑坡稳定性的影响

Influence of drawdown of reservoir water level and rainfall on Xiaping landslide stability

三峡库区库岸有众多滑坡发育,受库水位升降和降雨影响,滑坡稳定性状态处于变化之中。为研究滑坡稳定性变化规律,以万州区下坪滑坡为例,采用极限平衡法与概率分析法,分析了库水位从159 m降至145 m阶段该滑坡的稳定性状态。在设置库水位降速时考虑现状值与期望值两种情况,从降雨量和降雨持续时间两个角度考虑50年一遇降雨条件。分析结果表明:(1)在增大库水位下降速率的条件下,下坪滑坡稳定性降低,破坏概率变大。(2)在相同的降雨时间内,单日降雨量越大,滑坡稳定性降低越快;在库水位降速与单次总降雨量一定时,降雨持续天数越长,滑坡稳定性最差。(3)单次总降雨量一定时,滑坡破坏概率随降雨天数增加而增大,其速率表现为由快变慢,稳定性系数随降雨天数增加而减小,其速率表现为由快变慢。(4)从定性和定量两方面分析,在1.2 m/d降速+14 d降雨条件下,下坪滑坡稳定性状态最差,处于低危险性、基本稳定状态。

There are many landslides developed on the bank of the three gorges reservoir. Affected by the variation of the reservoir water level and rainfall,the stability of the landslides is in change. The Xiaping landslide in Wanzhoudistrict is taken as an example to study the variation of the stability of the landslide.Analyzing the stability of the Xiaping landslide during the water level drops from 159 m to 145 m with the method of the limit equilibrium method and probability analysis. The present value and the expected value are taken into the consideration when set up the reservoir drawdown. And the rainfall condition of once every 50 years is related to rainfall and the duration of rainfall. The results showed that： 1. The stability of the Xiaping landslide decreases and the failure probability increases with the increase of the rate of the reservoir water level. 2. The greater the daily rainfall becomes,the faster the stability of the landslide decreases,during the same rainfall time. And when the decline rate of the reservoir water level and the single total rainfall are same,the longer the rainfall last,the worse the stability of the landslide. 3. When the total rainfall is certain,the increase rate of the failure probability goes slow and the decrease rate of the stability goes slow,with the increase of the rainfall duration. 4. Analyzing the stability of the Xiaping landslide from two aspects of qualitative and quantitative,thestate is the worst,which can be divided into the low risk and general stable state,under the conditions that the rate of the reservoir drawdown is 1. 2 m/d and the rainfall duration is 14 days.