基于蒙特卡洛法的滑坡稳定性二元指标评价研究

Monte-Carlo method-based study on dual index evaluation of landslide stability

土体抗剪强度参数(c和φ)统计特性、库水位升降及降雨耦合下对滑坡可靠性的影响较大,而目前研究不足。通过蒙特卡洛模拟开展了白水河滑坡不同土性参数变异系数、相关系数组合下库水位升降及降雨的稳定性计算,得出了最不利组合下的安全系数可靠值。结果表明:滑坡失效概率随土体抗剪强度(c和φ)相关系数增大而减小。不考虑相关性容易引起对滑坡可靠性偏保守的估计,库水位上升、库水位下降和降雨三种工况下滑坡失效概率最大值分别为考虑相关时最小值的1. 7倍、31倍和29. 5倍。相同库水位变化速率下,库水位下降比上升时的失效概率显著增大。两种工况下最大失效概率分别为38. 81%和17. 94%。库水位下降叠加降雨时滑坡稳定性最差,安全系数可靠值为0. 67,c、φ变异系数均取0. 5,不考虑相关性为其参数最不利组合;中值安全系数分析滑坡稳定性时偏高,二元指标体系评价滑坡的稳定性更符合实际。

Thecoupling of statistic characteristics of soil shear strength parameters(c andφ),the rise and fall of the reservoir water level and rainfall has a great influence on landslide reliability,but the problem is not studied sufficiently in the past.Through Monte Carlo simulation,the calculation on the stability of Baishuihe Landslide during rise or drawdown of the reservoir water level and rainfall under various combinations of soil parametric variation coefficient and correlative coefficient is carried out,and then the reliable value of the safety coefficient under the most unfavorable combination is obtained.The result shows that the failure probability of the landslide decreases along with the increase of the correlative coefficients of the soil shear strength(c andφ).Without the consideration of that the correlation is prone to lead to a little bit conservative estimation of the reliability of the landslide,the maximum values of the failure probability of the landslide under the operation conditions of rise of the reservoir water level,drawdown of the reservoir water level and rainfall are 1.7 times,31 times and 29.5times of the minimum values under the consideration of the correlation respectively.Under the same changing rate of the reservoir water level,the failure probability during the drawdown of the reservoir water level significantly increases,if it is compared with that during the rise of the reservoir water level.The maximum failure probabilities for both the operation conditions are 38.81%and 17.94%respectively.Without the consideration of that the correlation is the most unfavorable combination of its parameters,the stability of the landslide is the worst during the drawdown of the reservoir water level superimposed with rainfall,for which the reliable value of the safety coefficient is 0.67,while 0.5 is taken for the variation coefficient of c andφ.As the medium value is a little bit higher for analyzing the stability of the landslide,the dual index system is more realistic to be adopted for the evaluation concerned.