降雨过程中滑体非饱和带的滞水量计算分析

Assessment for backwater amount in unsaturated zone in landslide in rainfall process

为研究滑体中的非饱和带滞水在降雨补给潜水过程中的作用,提出降雨过程中非饱和带滞水的计算方法以及以非饱和带滞水为指标的降雨阈值评价方法.通过监测降雨量、坡体潜水位及排水结构的排水流量,建立统计模型来评估降雨产生的非饱和带滞水量.利用排水隧洞影响范围内的坡体模型和均匀渗流理论正坡浸润线分析了潜水位变化所对应的土体中潜水释水量,使潜水位通过量纲变换后与降雨量和排水流量量纲一致,从而进行三者的统计模型分析.利用坡体高度饱和条件下降雨过程的监测数据建立向量自回归模型,用于计算理论降雨量,得到低水位条件下降雨过程中产生的非饱和带滞水量.根据浙江省杭金衢高速公路K103滑坡的案例,采用三次暴雨过程中的降雨、排水隧洞排水流量与潜水位监测值对降雨过程中产生的非饱和带滞水量进行了计算,分析了非饱和带滞水量对降雨补给潜水过程所起的作用,结果表明:可以将当滞水量重量达到60kN且地下水位达到0.6m时作为指标来确定降雨阈值.

To analyze the effect of backwater in unsaturated zone in the process that rain fed the groundwater in landslide, the computing method for backwater amount in rain process and evaluation method for rainfall threshold with the index of backwater were presented. The backwater amount induced by rainfall was deduced from the statistical model which was based on the monitoring data containing rainfall, groundwater level in landslide and water discharge from drainage structure. To make dimensions consistency of the monitoring data from rainfall, water discharge and groundwater level for statistical analysis, a seepage field model of drainage tunnel was established. In this model, the groundwater level variation was related to water release quantity considering the line of seepage in positive slope in uniform flow theory. In the situation of highly saturated, a vector autoregression model was established based on the data from dimensional transformation of groundwater level, monitoring data of rainfall and water discharge in the rainfall process. It could compute theoretical rainfall intensity, so that the backwater amount in the situation of low groundwater level was deduced in the rainfall process. The monitoring data of rainfall, water discharge in drainage tunnel and groundwater level from three heavy rainfall processes in K103 landslide at the Hangzhou-Jinhua-Quzhou Highway were analyzed. The generated backwater amount was calculated and its effect in rainfall infiltration into groundwater was analyzed. It concluded that the rainfall threshold was that the gravity force of backwater amount reaching 60 kN and the groundwater level reached 0.6 m.