多孔连续介质渗透压力对变形应力影响的数值模拟方法探讨

渗流场对应力和变形影响计算中渗流荷载普遍采用渗透体积力+浮托力方式,这是一种简化近似算法,即忽略了渗透压力作用下固体介质自身的变形。这种近似对于土、砂等细颗粒离散介质的误差是可以忽略的,但对于混凝土、裂隙岩体等多孔连续介质或等效孔隙介质则因忽略了孔隙压力对固体介质变形的影响,夸大了浮托力的作用,导致变形和有效应力失真。本文从孔隙水压作用下的应力应变关系出发,将孔隙压力的作用按初应变(或初应力)推导有限元渗透荷载公式(孔隙压力初应力/应变法)。用算例比较了不同方法对结果的影响,结果表明,渗透体积力+浮托力的算法,有效应力和变形误差过大,有些情况下会得到错误的变形结果。而孔隙压力初应力/应变法,可以正确地得到渗流场中渗透压力作用下的应力和变形。

Study on numerical simulation method used in analyzing the effect of seepage pressure in continuous medium with pores on deformation and stress

Seepage force and uplift pressure are often used to analyze seepage field''s influence on deformation and stress, which is a simplified proximal algorithm ignored solid media''s own deformation under pore pressure. For fine-granular medium like soil and sand,this self-deformation can be ignored,but for continuous medium with pores like concrete and rock with cracks, the neglect of pore pressure''s effect on solid medium and overestimate of uplift pressure will misestimate the deformation and effective stress. From the perspective of stress-strain under pore pressure, regarding the pore pressure as initial strain (initial stress), the paper derives the finite element formula for seepage load (named "initial strain/stress" method). Comparing different results getting from different calculation methods, it shows that from the calculation using seepage force and uplift pressure as seepage load, the obtained deformation and effective stress appear too large error and sometimes are even wrong, while the "initial strain/stress" method can come to correct result of deformation and stress.