压力板仪不仅可用于测试非饱和土的减湿曲线,还能测试其增湿曲线,对研究土壤与水分之间的物理关系具有重要意义。针对当前压力板仪的不足,提出了利用电子压力表组提高吸力控制的精度,利用电子天平与蒸发校正对照组实现了精确量测土样中水分质量的变化,建立了数据采集系统避免了人为读取数据造成的误差积累,大幅提高了土水特征曲线测定的精度。利用该设备对毛乌素砂进行了试验,并利用Van Genuchen、Gardner、Fredlund and Xing土水特征曲线函数模型对试验数据进行了拟合分析,发现这三种模型对毛乌素砂均有较好的拟合效果;通过几何作图法确定了毛乌素砂土水特征曲线减湿曲线陡降段与增湿曲线陡降段的分界点。
Retrogressive landslides are common geological phenomena in mountainous areas and on onshore and offshore slopes. The impact of retrogressive landslides is different from that of other landslide types due to the phenomenon of retrogression. The hazards caused by retrogressive landslides may be increased because retrogressive landslides usually affect housing, facilities, and infrastructure located far from the original slopes. Additionally, substantial geomorphic evidence shows that the abundant supply of loose sediment in the source area of a debris flow is usually provided by retrogressive landslides that are triggered by the undercutting of water. Moreover, according to historic case studies, some large landslides are the evolution result of retrogressive landslides. Hence the ability to understand and predict the evolution of retrogressive landslides is crucial for the purpose of hazard mitigation. This paper discusses the phenomenon of a retrogressive landslide by using a model experiment and suggests a reasonably simplified numerical approach for the prediction of rainfall-induced retrogressive landslides. The simplified numerical approach, which combines the finite element method for seepage analysis, the shear strength reduction finite element method, and the analysis criterion for the retrogression and accumulation effect, is presented and used to predict the characteristics of a retrogressive landslide. The results show that this numerical approach is capable of reasonably predicting the characteristics of retrogressive landslides under rainfall infiltration, particularly the magnitude of each landslide, the position of the slip surface, and the development processes of the retrogressive landslide. Therefore, this approach is expected to be a practical method for the mitigation of damage caused by rainfall-induced retrogressive landslides.
LIN HungchouYU YuzhenLI GuangxinYANG HuaPENG Jianbing
