Construction of a Vertical Grouting Curtain and Numerical Evaluation of Its Water-Blocking Effectiveness in a Water-Rich Volcanic Polymetallic Deposit

Groundwater inflow through fractured volcanic aquifers and water-conducting structures threatens deep mining of concealed polymetallic deposits. We evaluated a vertical grouting curtain at the Huangtun pyrite deposit in the Luzong volcanic basin, China. Geological investigations, grouting records, and two large-scale multi-well pumping tests informed three-dimensional FEFLOW models of the pre- and post-curtain groundwater systems. Hydraulic heads from the two tests constrained model calibration, while boundary-specific water budgets characterized residual lateral inflow. The southern, central, and western curtain sections were integrated with natural low-permeability boundaries, although an ungrouted southeastern gap remained. Calibrated hydraulic conductivities in several principal curtain zones were 0.005–1.26 m/d, whereas two central zones had higher values of 8.26 and 4.26 m/d, indicating heterogeneous hydraulic performance. Under prescribed post-curtain mining scenarios, predicted total inflow increased from 38,738.2 m3/d at −240 m to 46,449.2 m3/d at −340 m. The southeastern gap IJ was the largest individual inflow pathway, followed by the southern curtain segments HI and GH. Relative to paired no-curtain scenarios, overall water-blocking efficiencies were 60.00% and 57.26% at these levels, while the tabulated local efficiencies were 70.43% and 68.02%, respectively. At −290 m, the model predicted a drawdown cone within its 1.65 km2 domain; a separate lumped calculation estimated approximately 9.98 million m3 of elastic groundwater-storage release. The available model and observations could not establish the regional radius of influence or quantify ground deformation. The integrated curtain–geological barrier therefore substantially reduced modeled mine inflow, but the ungrouted gap and locally conductive curtain zones sustained residual recharge under deeper mining conditions. These findings identify priority sectors for reinforcement and support drainage design and groundwater monitoring.