摘要
多孔介质在应力作用下具有弹性变形和黏性变形两种完全不同的变形机制.多孔介质的弹性变形是由介质的本体有效应力所致,而黏性变形则是由介质的结构有效应力所致.多孔介质的总变形为弹性变形和黏性变形的叠加.计算多孔介质总应变量的流变模型必须同时采用本体有效应力和结构有效应力(双重有效应力),而传统的流变模型仅采用Terzaghi有效应力是不妥当的,它无法正确描述多孔介质的应变行为.采用了双重有效应力之后的流变模型,通过调节介质物性参数,可以拟合介质的实际应变行为,并且把多孔介质与普通固体联系了起来.
Porous media are a special kind of material, which consists of skeleton particles and pores between. Pores are usually saturated with one or several kinds of fluids. Normally, porous media suffer both an outer stress (total stress) and an inner stress (pore pressure or fluid pressure) simultaneously. So, an effective stress is necessary in the study of deformation behavior of porous media. The effective stress is an equivalent stress, which alone yields the same strain behavior with the two stresses applying on porous media outside and inside. K.Terzaghi proposed the first effective stress of porous media for soil mechanics in 1923, which is the simple difference between the outer stress and the inner stress. The Terzaghi effective stress concept is widely used not only in soil mechanics but also in rock mechanics. However, a recent research discovered that porous media have two effective stresses: the Primary effective stress and the Structural effective stress, named as the Double Effective Stresses of porous media. Actually, the Terzaghi effective stress is only an approximation to the structural effective stress.Corresponding to the Double Effective Stresses, porous media have two kinds of deformation mechanism: the elastic deformation (the Primary deformation) and the viscous deformation (the Structural deformation), which is related to the special material structure of porous media. The primary effective stress yields elastic strain in porous media while the structural effective stress yields viscous strain. The total strain of porous media is the sum of elastic strain and viscous strain. The rheological model to calculate the total strain of porous media must adopt both the primary effective stress and the structural effective stress(the double effective stresses) for the calculations of elastic strain and viscous strain respectively. However, the conventional rheological model adopts the Terzaghi effective stress alone to calculate the two kinds of strain, which cannot fit the strain behavior of porous media properly. The new model with double effective stresses, proposed in this paper, can simulate practical strain behavior of porous media and also unite porous media and solids through property parameters.
出处
《力学学报》
EI
CSCD
北大核心
2003年第2期230-234,共5页
Chinese Journal of Theoretical and Applied Mechanics
关键词
多孔介质
有效应力
应变
黏弹性
流变模型
porous media, effective stress, strain, viscoelasticity, rheological model
