库区水位下降对库岸边坡稳定性的影响

Influences of reservoirs water level drawdown on slope stability

为了研究库区水位下降过程中岸坡的稳定性,在探讨库岸边坡稳定性影响因素的基础之上,通过数值计算与稳定性分析理论,同时考虑坡度、坡体渗透系数与库区水位下降速率的不同工况条件下渗流场中孔隙水压力的变化,并对库区水位下降期间各因素变化对边坡稳定性系数的影响进行了分析.研究结果表明:库区水位下降对库岸边坡的稳定性有着较大影响,是库区边坡失稳破坏的重要因素,当水位下降时,库岸边坡稳定逐渐降低.采用FLAC对不同工况进行数值计算,当研究参数取值在符合工程实际范围内时,相同水位下降速率条件下库岸边坡坡度逐渐增加时,边坡稳定性呈现逐渐下降趋势;坡体渗透系数逐渐减小时,边坡稳定性也越来越低.而不同的水位下降速率对边坡稳定影响也不同,当水位下降高度相同时,下降速率逐渐增大则边坡的稳定性逐渐降低;坡度、水位下降速率与坡体渗透系数的变化都会导致边坡稳定系数的变化,其中库区水位下降过程中存在着稳定性系数最小值,水位下降速度越大,最小值越小;此外,库水位下降时存在一个最危险水位,此时坡体稳定性系数最小,而该水位大致位于坡体下1/3处.研究结果对三峡库区水库水位的调控和库岸边坡的稳定性具有一定的工程意义.

To investigate the influences of reservoir water level drawdown on slope stability,numerical simulation together with theoretical analysis are carried out to examine the impacts of slope angle,slope permeability and water level drawdown speed on pore water pressure change during seepage,as well as the slope stability number.It is found that the reservoir water level drawdown,as the main contributing factor,possesses significant influence on slope stability.Slope stability decreases with reservoir water level drawdown.Based on the numerical results,with the same water level drawdown speed,slope stability decreases gradually as slope angle increases from 15°to 30°.It also decreases when the slope is becoming less permeable,from 8.64 m/d to 0.086 4 m/d.In addition,with the same water level drawdown magnitude,stability worsens when the water level drawdown speed increases from 1 m/d to 2 m/d.All results above meationed indicate that there are interaction effect between slope angle water level,drawdown speed and slope permeability,with regard to the influences on slope stability.Furthermore,there exists a most dangerous water level,at about 1/3 height from the slope bottom,under which the stability number is the minimal.The results have certain engineering significance in reservoir volume management and regulationfor the Three Gorges and stability design and analysis of highway bank slopes.