西安白鹿塬北缘黄土边坡稳定的可靠度分析

在西安白鹿塬北缘实测了14个黄土自然边坡断面,建立了地质模型,通过采样测试并收集已有的测试资料,获得了各时代黄土地层的物理力学参数,将Morgenstern-Price法稳定性计算公式作为极限状态方程,分别采用Monte-Carlo法和Duncan法进行了边坡稳定的可靠度分析。结果表明:采用Monte-Carlo法和Duncan法得到的14个边坡稳定系数分别为1.11～1.41和1.09～1.33,显示这些边坡处于基本稳定—稳定状态;采用上述两种方法得到的边坡可靠指标分别为0.56～1.79和0.39～1.60,得到的失效概率分别为3.4%～29.0%和5.5%～34.8%,并且共有75%的边坡失效概率大于10%,失效可能性较大。统计结果表明:白鹿塬区边坡的坡高和坡度存在负相关性。低而陡的边坡潜在最危险滑面剪出口较高,失效概率较小;坡高达到50m及以上时,边坡高而缓,剪出口较低,失效概率较大,其中河流下切深,有N2泥岩出露的极高边坡,稳定性最差。Duncan法求解的稳定系数略小于Monte-Carlo法求得的结果,而前者求解的失效概率略大于后者,两种方法计算结果较为接近。由于Duncan法理论简单,计算量小,更宜于在实际工程中应用。

Reliability analysis for stability of loess slopes along the northern edge of Bailuyuan,Xi’an

The sections of 14 loess natural slopes were measured along the northern edge of Bailuyuan,Xi’an,and then the geologic models were built.The parameters of physical mechanics of loess strata in different periods were obtained by in-suit testing and collecting data.Monte-Carlo Method and Duncan Method were used for slope reliability analysis based on the limit state equation of Morgenstern-Price Method.The results showed that the stability coefficients of 14 slopes calculated by Monte-Carlo Method and Duncan Method were 1.11-1.41 and 1.09-1.33 respectively,and the slopes were basically stable-stable;the reliable indicator of slopes calculated by the above methods were 0.56-1.79 and 0.39-1.60 and the failure probabilities of slopes were 3.4%-29.0% and 5.5%-34.8%,respectively;the failure probabilities of 75% slopes were more than 10%,and the failure Likelihoods were high.The statistical results indicated that the relationship between height and gradient of slopes was negative.The landslide shear crack of most dangerous potential slip surface in the low-steep slope was high,and the failure probability was small;when the height of slope was 50 m or more,it was high and slight,the landslide shear crack was low,the failure probability was high,and because of the deep stream trenching,there was highest slope in mudstone from strata N2,and the stability was most poor.The stability coefficients calculated by Duncan Method were a little less than that by Monte-Carlo Method,the failure probabilities calculated by the former were a little more than that by the latter,so the results calculated by the two methods were close.Because of the simple theory and small amount of calculation,Duncan Method was more appropriate for practical engineering.