Pre-excavation Grouting to Prevent Water Inflow of Jointed Rock in Underground Construction

Fracture frequency information was acquired by drilling for pre-excavation grouting for underground construction fracture water inflow. The permeability coefficient of the surrounding rock mass was measured by pump-in tests on each section. The measured data were analysed by employing statistical methods to determine their statistical rules. According to the water inflow calculation theory, in combination with the designed water inflow control criterion, the minimum value for the fracture width to be sealed was calculated, which provides a criterion for the selection of grouting materials. According to this, the spreading rule was analysed, and grouting methods and parameters were determined. The flow dimension theory was used to analyse the pressure-quantity-time curves during grouting. After grouting, the sealing efficiency was evaluated by excavation. The results show that obvious water seepage existed in the vault and side walls, which reached requirement on seepage water control criterion of no more than 0.01 m³/h. The actual water inflow was 50% lower than the predicted value, which was within the acceptable range.