渗透各向异性对基坑工程性状的影响研究

Study on the Effect of Anisotropic Permeability on the Behavior of an Excavation

天然沉积的土体在结构构造上呈现出各向异性特征,因而在渗透上也呈现出各向异性特征。基于比奥固结理论,开发出了考虑渗流与土骨架变形耦合的三维基坑有限元程序,分别分析竖向渗透系数不变时和水平向渗透系数不变时渗透各向异性对基坑变形的影响。研究表明,无论是水平向渗透系数不变还是竖向渗透系数不变时,随着渗透各向异性系数的增大,支护结构的水平位移都增大,坑外较远距离处的地表沉降都减小;但对于坑底隆起变形,则是当水平向或者竖向渗透系数不变时,另一个方向的渗透系数越大,坑底的隆起变形量越大。因此,在进行基坑工程建设时,应考虑渗透各向异性的影响。

Natural sedimentary soil shows the characteristics of anisotropy in fabric structure,thus also shows the characteristics of anisotropy in permeability. Based on Biot＇s consolidation theory,a three-dimensional finite element program for excavation was developed considering the coupling of seepage and deformation of soil skeleton. The effect of anisotropic permeability on the behavior of excavation was analyzed when the vertical or horizontal permeability coefficient of soil is constant respectively. Studies show that the horizontal displacement of supporting structure increases and ground settlement at a certain distance from retaining structure decreases with the increase of permeability anisotropy coefficient. However,when the horizontal or vertical permeability coefficient is constant,heave deformation of pit base is larger with the increase of permeability coefficient on another direction. Therefore,anisotropic permeability of soil should be considered when an excavation is constructed.