The Study of Coupling Law of Stress Field / Seepage Field in Permeable Stratum Medium

According to the basic theory of rock mechanics, fluid mechanics in porous medium, geologic mechanics, calculated mechanics and fluid-solid coupling seepage, a mathematical and numerical model of seepage field and stress field coupling is developed in porous medium and a computer program is designed with the method of finite element technique. The Coupling Law of Seepage field /Stress field in Permeable Stratum Medium is studied. The depedence of stress-strain on time, space and rock physical properties parameters around borehole of permeable rock medium was obetained with the the method of numerical simulation. It can be seen from result that the pore space flow field pressure influences elastic-plastic change of stratum in two sides. One is the decrease of payload in the borehole wall and far field boundary. At the moment, the effective sustain payload of borehole wall decline to zero, while the effective sustain payload of far field boundary is the difference between crustal stress and pore fluid pressure. The other is pressure gradient effect of borehole in the pore Stratum Medium, influenced by inhomogeneous pore fluid. As a kind of volume force, pore pressure gradient directly influences and control balance and variant of Stratum Medium unit, influencing average pressure at the same time. Underpermeability borehole wall circumstances, when the pore pressure-Pp of farfield reach 15 Mpa, the borehole wall nearby has big-range plastic deformation. The largest plastic deformation DMX in the direction X and Y is 2.132. With far field pore pressure further increasing, when the Pp are 21 and 24 Mpa, the largest plastic deformation DMX in the direction X and Y are 1.301 and 1.284. The bore hole yield region will not change obviously.