Computational modeling of seepage in a fractured rock mass during tunnel excavation: a case study from Liaoning Province, China

The research team's developed GeoSMA-3D (three-dimensional geotechnical structure and model analysis) program was used to enable the visualization analysis of tunnel engineering by determining information about the key blocks and the deterministic fracture surfaces in Diaoyutai Tunnel in Liaoning Province, China. The seepage characteristics of rough fractures with varied intersecting angles were investigated under excavation disturbance, and the effective permeability of the surrounding rock blocks was estimated. Three-dimensional morphology scanning and a point cloud splicing algorithm were used to characterize the geometric properties of the rough fractures quantitatively. The numerical model of rough fractures with varied intersecting angles was investigated via COMSOL Multiphysics software. Besides this, the seepage characteristics (as flow velocity distribution and the water pressure evolution) in the rough fractures were simulated and analyzed. The simulation results assisted in understanding the evolution of seepage characteristics in rough fractures with varied intersecting angles under different stresses. In this study, for rock matrix, the anti-analysis technique was employed to import the kriging method into MATLAB based on the surface permeability of the rock blocks. Furthermore, the cuboid model developed by COMSOL (TM) and MATLAB was used to characterize the internal permeability of the rock blocks to obtain the effective permeability by using the obtained permeability spatial distribution. In this context, the total flow through the nonuniform area was estimated and the geometric mean was proposed as an appropriate measure. Moreover, the developed program provides a nondestructive method to estimate the effective permeability of large rock samples under excavation disturbance.