基于降雨强度-历时评价边坡稳定性--以安徽省3个边坡为例

Evaluation of Slope Stability Based on Rainfall Intensity-duration—Taking Three Slopes in Anhui Province,China as Examples

为了探究降雨条件对边坡稳定性的影响,确定降雨阈值曲线,利用FLAC 2D 7.0数值模拟软件对安徽省3个小型边坡进行饱和-非饱和渗流及稳定性分析,获取了边坡安全系数随降雨强度和历时的变化趋势。边坡监测位置处孔隙水压力与饱和度的变化结果显示:降雨对边坡的影响是有限的,降雨历时越长,极限降雨强度越小并趋于稳定,边坡趋于饱和,此时安全系数达到最小值,后续降雨对边坡安全系数影响很小;为确保安全,假设临界安全系数为1.15,对应降雨强度为临界降雨强度,降雨历时越长,临界降雨强度越小并趋于稳定,3个边坡临界降雨强度趋于稳定时分别为13、12和16 mm·d-1,对应的降雨历时分别为5、9和12 d,表明前期降雨对边坡稳定性影响很大。利用这3个边坡的临界降雨强度数据进行降雨阈值曲线拟合,并以435组安徽省2008~2022年历史灾害降雨数据验证该降雨阈值曲线。结果表明:95%以上的灾害数据点可以被该降雨阈值曲线预测。

Landslides are one of the most common geological hazards,with rainfall being the main trigger for their occurrence.In order to find the impact of rainfall conditions on slope stability and determine the rainfall threshold curve,the saturated-unsaturated seepage and stability analysis of three small slopes in Anhui province was carried out using FLAC 2D 7.0 numerical simulation software,and the changing trend of safety factor of slopes with rainfall intensity and duration was obtained.The results show that the influence of rainfall on slopes is limited;the rainfall intensity corresponding to the minimum safety factor of slopes during the rainfall infiltration process is the ultimate rainfall intensity,and the longer the rainfall duration,the smaller the ultimate rainfall intensity becomes and tends to stabilize;the changes in pore pressure and saturation at the monitoring location on the slope further verify that the slope tends to become saturated under ultimate rainfall intensity,resulting in the minimum safety factor.Subsequent rainfall has little effect on the safety factor of slope.To be on the safe side,a critical safety factor of 1.15 was assumed,and the corresponding rainfall intensity was defined as the critical rainfall intensity.Similar to the trend of ultimate rainfall intensity,the longer the rainfall duration,the smaller the critical rainfall intensity becomes and tends to stabilize.The critical rainfall intensities for the three small slopes tend to stabilize at 13,12,and 16 mm·d-1,respectively,with corresponding rainfall durations of 5,9,and 12 d.It is indicated that under the influence of long-term early-stage rainfall,a small amount of rainfall can cause slope instability and failure.Additionally,the critical rainfall intensity data of these three small slopes(simulated data points for geological disaster rainfall)were used to fit the rainfall threshold curve,and the accuracy of the rainfall threshold curve was validated with 435 sets of historical rainfall data for geological disasters in Anhui province from 2008 to 2022.The verification results show that over 95%of actual disaster rainfall data can be predicted by the rainfall threshold curve.