考虑土体非饱和特性的斜坡降雨入渗模型及边坡稳定性分析

降雨入渗是诱发滑坡的关键因素,研究斜坡降雨入渗规律对于滑坡的预测与防范具有重要意义。传统的Green-Ampt模型及改进的Green-Ampt模型均假定入渗过程为均匀饱和入渗,忽略了入渗过程中湿润锋锋面上方非饱和区的存在。针对这一不足,首先,基于达西定律分析斜坡内基质吸力的分布规律;然后,结合非饱和土VG模型得到了斜坡内湿润区含水量沿深度变化的函数关系;最后,基于改进的Green-Ampt模型推导了考虑土体非饱和特性的斜坡降雨入渗模型,并将其引入到无限斜坡稳定性分析当中。研究结果表明:与数值解和现有模型相比,考虑土体非饱和特性的降雨入渗模型能更加准确地反映降雨入渗的过程,基于改进模型计算的稳定性系数较好地揭示了恒定降雨强度下斜坡稳定性的变化规律,证明了该方法的正确性和适用性。

Rainfall Infiltration Model and Slope Stability Analysis in Consideration of Unsaturated Soil Characteristics

Rainfall infiltration is a key factor which induces landslides. Researching the law of rainfall infiltration in slope is of crucial significance for the prediction and prevention of landslides. The traditional Green-Ampt model and the improved Green-Ampt model both assume that the infiltration process is uniform and saturated, ignoring the existence of unsaturated zone above the wetting front. In view of this, we analyzed the distribution law of matric suction in slope first of all based on Darcy’s law; and in subsequence, we obtained the functional relation of water content in the wet zone of slope varying with depth in association with the VG model of unsaturated soil; finally, we derived a rainfall infiltration model considering the unsaturated characteristics of soil using the improved Green-Ampt model, and applied the model into infinite slope stability analysis. Results demonstrated that, compared with numerical solution and existing models, the proposed infiltration model in consideration of the unsaturated characteristics of soil reflects more accurately the process of rainfall infiltration. In addition, the stability coefficient calculated based on the proposed model better reveals the change rule of slope stability under constant rainfall intensity, which proves the correctness and applicability of the model.