FRACTAL TREELIKE FRACTURE NETWORK MODEL FOR HYDRAULICALLY AND MECHANICALLY INDUCED DYNAMIC CHANGES IN THE NON-DARCY COEFFICIENT DURING THE PROCESS OF MINE WATER INRUSH FROM COLLAPSED COLUMNS

Abstract

An accurate and reliable mathematical model for water inrush can help ensure operational safety in coal mines. In this study, a numerical model for water inrush caused by collapsed columns that couples mechanical rock deformation with flow in porous media based on a fractal treelike fracture network was developed. In particular, the proposed model considers collapsed columns and mining damage zones as fractal dual-porosity media. The model incorporates Darcy’s law, the Brinkman equation, and the Navier–Stokes equation to govern the groundwater flow. The Brinkman equation was adopted to simulate the groundwater flow in collapsed columns, for which the non-Darcy coefficient can be derived based on damage criteria for the fracture zone. To simulate the dynamics of water inrush in collapsed columns, the finite element method was used to solve the governing equations for the groundwater flow, solid mechanics, and rock damage. The proposed model was validated against two sets of field data, and the results showed that dynamic changes in the non-Darcy coefficient could be used to identify the occurrence of water inrush, which can be employed to improve mining safety.