长期浸水作用下重塑黄土渗透特性变化规律分析

Analysis on changing law of permeability of remolded loess under long-term soaking

为探究长期浸水作用下黄土渗透性变化特性,针对黑方台因长期灌溉作用导致台塬整体不断产生沉陷,下部黄土处于长期浸水状态,浸水作用下黄土性质也随之变化等问题,采用室内变水头试验和电镜扫描试验对浸水与未浸水黄土进行对比,研究两种工况下黄土渗透性变化规律。结果表明:长期浸水作用使黄土渗透性降低;浸水与未浸水两种工况黄土渗透性均随干密度和初始含水率增大而减小,黄土渗透性与干密度拟合曲线符合指数函数关系,相关系数大于0.963;相同干密度与初始含水率条件时,浸水工况相较未浸水工况黄土渗透性低10%;浸水工况黄土渗透性降低主要是由于黄土颗粒间胶结物质溶解导致黄土内部结构变化引起。浸水作用下黄土渗透性研究对预测台塬地下水位变化以及滑坡防治具有积极意义。

In order to explore the changing characteristics of the permeability of loess under the effect of long-term soaking and aim at the problems from Heifangtai Tableland,i.e.the continuous whole subsidence of loess tableland caused by long-term irrigation,the underlying loess under the status of long-term soaking,the change of the loess property along with the soaking effect,etc.,both the soaked and unsoaked loesses are compared with in-door variable head permeability test and electron microscopy test,and then the changing laws of the loesses under both the conditions are studied.The result shows that the effect of long-term soaking makes the permeability of loess decreased.The permeabilities of both the soaked and unsoake loesses are decreased along with the increases of the dry density and initial water content,while the fitting curve between the permeability of loess and the dry density is consistent with the relationship of exponential function with the correlation coefficient beyond 0.963.Under the same conditions of dry density and water content,the loess permeability under soaking condition is lowered by 10%than that under the unsoaking condition.The decrease of loess permeability under soaking condition is mainly caused by the change of the internal structure of loess due to the dissolution of the cementing substances among the particles of loess.The study on the loess permeability under soaking condition has an active significance for predicting the change of groundwater level of tableland and preventing landslide.