水-力耦合作用下干燥和湿润砂质黄土渗透特性试验研究

Experimental study on seepage characteristics of dry and wet sandy loess under hydro-mechanical coupling

为探讨干燥和湿润砂质黄土在水-力耦合作用下的非饱和渗透特性,研制考虑水-力耦合效应的非饱和土渗透系数测量试验装置。针对不同初始含水率的干燥土柱和湿润土柱,采用湿润锋前进法开展一系列一维土柱渗流试验,得到水-力耦合作用下湿润锋、渗透系数与竖向变形的变化规律,并结合扫描电镜试验,揭示其微观机理。结果表明:(1)随入渗时间增大,湿润锋前进速率逐渐减小,并且干燥土柱的湿润锋速率明显小于湿润土柱;(2)轴向压力相同时,湿润土柱的渗透系数函数直线段斜率大于干燥土柱。随着轴向压力增大,两种类型土柱的渗透系数函数直线段斜率均略有减小。渗流稳定后,湿润土柱稳定渗透系数大于干燥土柱;(3)与湿润土柱相比,干燥土柱具有明显的水敏性,湿化后其变形量显著增大。该研究成果对揭示阳城隧道砂质黄土区围岩的渗透及变形机理,指导隧道安全施工具有重要的理论及实际意义。

A hydro-mechanical coupling apparatus is developed to explore the unsaturated hydraulic conductivity characteristics of dry and wet sandy loess under hydro-mechanical coupling action.Based on the test apparatus, a series of seepage tests on one-dimensional columns of sandy loess are carried out using the “the wetting front advancing method” for completely dry soil columns and wet soil columns.The variation laws of the wetting front, hydraulic conductivity, and axial deformation under the hydro-mechanical coupling are obtained, and the corresponding microscopic mechanism of sandy loess is studied with scanning electron microscope experiment.It is found that:(1) At the early stage of infiltration, the wetting front advancing velocity of the dry soil column and the wet soil column are approximately the same, while in the late period of infiltration, the wetting front advancing velocity of the dry soil column is significantly less than that of the wet soil column.(2) Given the same axial load, the slope of the linear segment of the hydraulic conductivity function curve of the wet soil column is greater than that of the dry soil column.With the axial load increases, the slopes of the linear segment of the hydraulic conductivity functions of the two types of soil columns decrease slightly.When the seepage flow is stable, the stable hydraulic conductivity of the wet soil column is greater than that of the dry soil column.(3) Compared with the wet soil column, the dry soil column has obvious water sensitivity, and after wetting its deformation increases significantly.The research results have important theoretical and practical significance for revealing the seepage and deformation mechanism of surrounding rock of the sandy loess of Yangcheng Tunnel and guiding the construction safety of the tunnel.