缓倾黄土滑坡稳定性分析及阈值研究——以廖集村滑坡为例

Stability analysis and thresholds for inclined loess landslide at Liaoji Village

以天水廖集村缓倾黄土滑坡为例,通过多种试验手段获取滑坡特征参数,建立非饱和入渗与稳定性分析的滑坡耦合模型,基于降雨入渗过程和斜坡失稳机制分析,着重在初始条件变化下,求得相应状态下考虑降雨过程的雨强-历时滑坡阈值.数值模拟结果表明:干燥状态下,土体下渗困难,仅对表层含水率影响明显,而湿润状态下,下渗迅速,基质吸力显著降低,在更短的时间滑坡即会失稳.故湿润状态下,降雨强度-历时滑坡阈值的判据标准低于干燥状态,降雨持时<150 h且雨强>1.2mm/h的组合区间即会发生滑坡,多为强降雨天气.干燥状态时,降雨持时>200 h,雨强为0.41～2.08mm/h为滑坡发生的优势组合区间,往往为连阴雨天气.

A study was made of an inclined loess landslide at Liaoji Village in Tianshui City. An unsaturated seepage and stability analysis numerical model was built, based on features of landslide obtained from field tests;to analyze the process of rainfall infiltration and instability mechanism, the warning criterion of typical initial state was established. As was shown in the numerical model, when in dry condition, water was difficult to infiltrate to the deep when moisture content was only in the surface. But in wet conditions, the seepage was rapid and unhindered, and the distribution of matric suction decreased obviously.As a result the slope would fail in a shorter time. The rainfall intensity-duration thresholds in corresponding initial state were proposed. The intensity-duration(I-D) threshold was lower in wet condition than that in dry condition, and duration <150 h rainfall intensity>1.2 mm/h would induce a landslide in a torrential rain. The duration >200 h and rainfall intensity ranging from 0.41-2.08 mm/h was a primary combination of I-D threshold in dry condition, being present in a continuous rain.