Practical Equivalent Continuum Model for Simulation of Jointed Rock Mass Using FLAC3D

The presence of gouge in rock joints significantly affects the physical and mechanical properties of the host rock mass. Wave-based exploration techniques have been widely used to investigate the effects of gouge fill on rock mass properties. Previous research on wave propagation in gouge-filled joints focused on analytical and theoretical methods. The lack of experimental methods for multiple rock joint systems, however, has limited the verification potential of the proposed models. In this study, the effects of gouge material and thickness on wave propagation in equivalent continuum jointed rocks are investigated using a quasi-static resonant column test. Gouge-filled rock specimens are simulated using stacked granite rock discs. Sand and clay gouge fills of 2 and 5 mm thicknesses are tested to investigate the effects of gouge material and thickness. Comprehensive analyses of the effects of gouge thickness are conducted using homogeneous isotropic acetal gouge fills of known thickness. The results show that gouge fill leads to changes in wave velocity, which depend on the characteristics of the gouge fill. The results also show that particulate soil gouge is susceptible to preloading effects that cause permanent changes in the soil fabric and contact geometry and that increased gouge thickness causes a more significant stiffness contribution of the gouge material properties to the overall stiffness of the equivalent continuum specimen. The normal and shear joint stiffnesses for different gouge fill conditions are calculated from the experimental results using the equivalent continuum model and suggested as input parameters for numerical analysis.

Download Full-text

Coupling Analysis of Seepage and Stress in Jointed Rock Mass of Equivalent Continuum

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.3493 ◽

2011 ◽

Vol 243-249 ◽

pp. 3493-3498

Author(s):

Tao Li Xiao ◽

Xin Ping Li ◽

Yi Fei Dai

Keyword(s):

Rock Mass ◽

Energy Criterion ◽

Jointed Rock ◽

Jointed Rock Mass ◽

Hydraulic Pressure ◽

Diversion Tunnel ◽

Continuous Mass ◽

Engineering Practices ◽

Equivalent Continuum ◽

Equivalent Continuous Mass

Under the action of stress and crack hydraulic pressure, the damage and rupture of jointed rock mass accumulate and extend simultaneously during the process of its crack occurrence and growth. The rock mass’s damage will be accumulated owing to its rupture, and the damage is closely related to the rupture. Taking into account comprehensive the stress intensity factors both of plane stress and plane strain for hydrous jointed rock mass, two new equations of crack propagation and the new crack length were built on the basis of energy criterion. Assuming the jointed rock mass as equivalent continuous mass with damage and introducing the damage constitutive equation of rock, the damage evolution of the hydrous jointed rock mass is simulated by the damage tensor and the damage strain. The model is used to simulate one tunnel. Through simulation, the waterhead contour is more smooth when the coupling is considered than is not considered, and the maximal displacement almost the same because the diversion tunnel was bulit.The simulate results can provide a reasonable recommendation to the engineering practices.

Download Full-text