降雨条件下双层土坡的模型实验研究

Physical Model Tests of Two-layer Soil Slopes under Rainfall

针对降雨入渗非均质土坡的稳定问题,建立双层边坡模型进行人工降雨实验,对坡体进行含水率和孔隙水压力监测,得到了非均质土坡在降雨条件下含水率和孔隙水压力更真实的变化。基于模型实验结果的分析,得出变化规律如下:①坡体渗流趋于稳定时,含水率、孔隙水压力不仅和深度有关系,而且也与土体物理性质有关。这与均质土坡的渗流状态明显不同;②坡体含水率、孔隙水压力在降雨过程中,响应时间随深度增大而增大。雨后过程中,下层土体含水率、孔隙水压力降低速度大于上层;③相同雨强条件下,坡体含水率和孔隙水压力随降雨历时而不断增大。降雨强度越大,坡体的孔隙水压力和含水率响应时间越早,但在坡体浅表层这种时间效应不明显;④对于降雨过程中能达到稳定渗流状态的土坡,前期降雨量主要影响降雨过程中含水率和孔隙水压力的变化。研究成果为降雨入渗条件下非均质非饱和土边坡的稳定分析提供了依据。

By constructing two-layer slope models and experiments under artificial rainfall, the water content and the pore water pressure in the nonhomogeneous slope are monitored continuously to obtain their rules of variation. The variations of monitored parameters of the two-layer slope are obtained as follows ： （ 1 ） The water content and pore water pressure of the heterogeneous slope are not only related with the depth but also the physical properties of soils under steady seepage, which is significantly different from that of homogeneous slope. （2） The response time of the water content and pore water pressure increases with the slope depth. After the rain the water content and the pore water pressure of lower layer decreases more rapidly than that of the upper layer. （3） Under the same rainfall in- tensity, the water content and the pore water pressure develop with the duration of rainfall. The response time is earlier if the rainfall intensity is higher, but the time effect is not significant nearby the slope surface. （4） If the slope seepage achieves a steady state during rainfall, the prophase rainfall mainly influences the water content and pore water pressure in the rainfall process. The research serves as a basis for the stability analysis of heterogeneous unsaturated soil slope in infiltration condition.