Grouting optimization for tunnel water-inrush disaster mitigation in jointed rock masses using discrete fracture network modeling

Groundwater flow in fractured rock masses, governed by discrete fracture networks (DFNs), critically impacts tunnel engineering safety. This study addresses water-inrush disasters by proposing a DFN-based grouting optimization method for jointed rock masses (Grades II–IV). The structural grid model is used to evaluate the degree of rock penetration in this area. Permeability coefficients and the radii of permeability ellipses are calculated at 30-degree intervals along the network, enabling comprehensive evaluation. Utilizing the least squares method, seepage ellipses are fitted to determine primary seepage coefficients. In consideration of the most unfavorable scenarios, rock mass seepage coefficients are selected for grouting design calculation. For each grade of surrounding rock mass, assessments are conducted to ascertain the water inflow of unlined tunnels, the water inflow of lined tunnels, and external water pressure on tunnel linings. Tunnel curtain grouting is required when the tunnel water inflow exceeds the design limits. Appropriate parameters for grouting ring thickness and permeability coefficients are selected to fulfill engineering specifications. In cases of excessive external water pressure in tunnel linings and significant inflow of water into the tunnel, it is recommended that grouting and lining operations are carried out after drainage and pressure relief in the tunnel. The DFN methodology enables targeted grouting that reduces water-inrush risks in high-risk zones.