各向异性渗透系数随应变场动态变化分析

ANALYSIS OF DYNAMIC CHANGES OF ANISOTROPIC PERMEABILITY COEFFICIENT WITH VOLUMETRIC STRAIN IN SEEPAGE COUPLING

渗透系数是应力场与渗流场相互影响、相互耦合的桥梁,只有建立渗透系数与应力场或应变场的关系式,才能体现应力场对渗流场的影响,实现真正的渗流耦合分析。基于三维比奥固结渗流耦合理论,以Kozeny-Caman方程为基础,建立各向异性渗透系数与体应变之间的关系式,利用FLAC3D中嵌入的FISH语言编制相应程序,对土体单元赋予动态的渗透系数,实现应力场对渗流场的影响,进而实现应力场、渗流场两场真正的渗流耦合分析,并以基坑工程为例进行算例验证。研究表明,渗透系数随应变场(应力场)的变化而变化,当产生负的体应变时,渗透系数减小,产生正的体应变时,渗透系数增大,而且体应变对水平向渗透系数的影响较大,为岩土工程的动态渗流耦合分析提供参考。

Permeability coefficient is a bridge of linking stress field and seepage field. Establishing relationship between permeability coefficient and stress field or seepage field can reflect the influence of stress field on seepage field and achieve real seepage coupling analysis. Based on three-dimensional seepage coupling Boit consolidation theory,the relationship between anisotropic permeability coefficient and volumetric strain is built on the basis of Kozeny-Caman equation,and relevant program is embedded with FISH program in FLAC3D software. Then soil mass unit is assigned dynamic permeability coefficients to reflect the influence of stress field on seepage field, realizing real seepage coupling analysis of stress field and seepage field. A case study of foundation pit is presented for validation. Result shows that permeability coefficient changes with strain field or stress field. The permeability coefficient decreases with negative volumetric strain but increases with positive volumetric strain. The volumetric strain has larger influence on horizontal permeability coefficient than vertical permeability coefficient. It may provide a reference for dynamic seepage coupling analysis of geotechnical engineering.