降雨条件下黄土斜坡的入渗特征分析

为研究黄土斜坡的降雨入渗规律和降雨诱发黄土滑坡的机理,在宁夏西吉县一黄土斜坡建立了监测站,在斜坡上部开挖探井并安装了土壤水分计观测土壤含水率,在探井附近安装了小型气象站,观测气温、降雨量、蒸发量。通过现场观测数据分析了气象条件对土壤含水率的影响,以及雨水在黄土斜坡中的入渗规律。使用SEEP/W软件分析了完整黄土斜坡和有裂隙黄土斜坡在临界降雨条件下的孔隙水压力分布,以及斜坡孔隙水压力随深度的变化规律。结果表明,深度1 m以内的土壤含水率变化受蒸发量与降雨量的影响显著,深度越大,土壤含水率的变化曲线越平缓。强度大于19 mm/d的降雨才会引起土壤含水率的骤增,且土壤含水率变化比降雨延迟48 h左右。斜坡表面发育的裂隙是雨水进入斜坡体内部的主要通道。降雨会在有裂隙的斜坡内部形成饱和区,使土体抗剪强度降低,饱和渗流会增加斜坡下滑力,这些作用使黄土斜坡发生滑动。现场监测研究得出了研究区滑坡临界降雨量的参考值,提出斜坡裂隙是降雨诱发黄土滑坡的重要因素。

Status-in-situ observation and analysis for the loess landslide under the impact of the rainfall

In the given paper,the author is inclined to have a sound master of the rain water infiltration regularity and its mechanism on the loess landslides induced by the rainfall by taking the results of a monitoring station of Xiji County,Ningxia Hui Autonomous Region,as a case study sample.What we have taken as our study sample is an exploratory well of 4.2 m deep on a slope.At the same time,we have armed ourselves with some soil moisture probes to test and observe the soil moisture data and information at the depth of O.5 m,1 m,2 m,3 m,and 4 m on the wall of the well.Thus,in so doing,we have succeeded in establishing a small weather-forecast station near the exploration well so as to monitor and collect the information and data of the temperature,rainfall and the evaporation.And,next,we have analyzed the influence of the climate and meteorological conditions on the soil moisture and infiltration distribution of the pore moisture pressure of the slope.The results of our observation and investigation show that the variation of the soil moisture content rate in the depth of 1 m is influenced significantly by the evaporation and rainfall,wherein greater depth may lead to more gentle variation in the curve of soil moisture.What is more,the rainfall over 19 mm/d intensity tends to cause a surge in the soil water content landslide loss at the surge in the soil water rate observed 48 h later than a heavy rain.In addition,the fissures of the slope surface proves to be the main channel for the rainwater to penetrate into the slope inside.Besides,when the strong rainwater gets into the slope through the ground fissure,it would result in a range of saturated area inside the slope.Thus,it can be seen that the saturation results prove the decrease of the soil shear moisture extent,with the increase of the sliding force due to the saturated seepage,thus aggravating the loess soil's quality.In the paper,we have illustrated the reference values of the landslide critical rainfall through the field monitoring and observation data,implying that the slope fracture is one of the key factors affecting the loess landslides as a result of rainfall,and serving as a reference to the geophysical disaster warning as well as the landslide prevention and control.