D transient elastic-viscoelastic-viscoplastic FEM analyses for stability of underground cavern located in dual-pore-fracture rock mass

Abstract

The rheological characteristics of dual-pore-fracture media are described by using Nishihara model, but the transient elastic, viscoelastic and viscoplastic elements of the model are composed of rock blocks and joint components, so the relative solving format of plane finite element method is established and introduced into the computation code developed by the authors. Aiming at the four conditions of surrounding rock mass of a rectangular underground cavern, in which the first rock mass is a whole (single medium) and the latter three are fractured by two sets of joints with different intersection angles (dual media), the numerical simulations are carried out, and the displacements, stresses and plastic zones in the surrounding rock masses are analyzed. The results show that the effects of multiple fracture sets may reduce the shear strength of intact rock mass, and change the distributions and values of stresses in the surrounding rock mass. Compared with the case of a single medium, the displacement directions of the surrounding rock mass of dual medium vary, the displacement values developing with time increase obviously, and there are also corresponding changes for the distributions of relative stress fields. With changes of the dip angles of fracture sets, the plastic zones in the surrounding rock mass of dual medium may be larger or smaller than that in the surrounding rock mass of single medium.