Influence of Alkali injection treatment on the deformation of tunnel surrounding rock rich in H2S

Alkali injection treatment is a key method for stabilizing surrounding rock containing H2S. To examine the deformation of surrounding rock with and without coal seams under different excavation methods and Alkali injection treatments, the finite difference method for single-hole Alkali injection, double-side-wall excavation, and three-bench excavation is simulated. The results indicate that, under the same excavation method, compared with no Alkali injection, the displacement of the vault increases by 23.37% to 24.33% for a 3% Alkali concentration and by 34.55% to 42.70% for a 5% concentration. The horizontal convergence of side walls increases by 18.20% to 25.53% for a 3% Alkali treatment and by 46.20% to 61.08% for a 5% Alkali treatment. When two coal seams tilt through the working face, the deformation of the lower layer is more significant than that of the upper. The greatest deformation occurs at the intersection of the lower layer and the excavation line. Under different Alkali injections, compared with the three-bench excavation method, the vault settlement of the double-side-wall excavation method decreases by 7.65% to 11.37% and the horizontal convergence of sidewalls decreases by 22.80% to 72.27%. When the surrounding rock contains coal seams and is treated with Alkali injection, it is recommended to use the double-sided excavation method.