Abstract: Aiming at the special requirements of the grouting material for the prevention of water inrush hazards in tunnels, the mechanical properties and anti-washout properties of the grout were improved by adding the admixture. The optimum mixing ratio of water to cement was obtained by testing the compressive strength and flexural strength of cement stone under different water to cement ratios, fiber contents and silica fume contents. The anti-washout characteristics and fluidity of the grout under the optimum mixing ratio were tested. It was found that the incorporation of fiber and silica fume with cement could significantly improve the strength of cement stone and had little effect on the fluidity of grout. At the same time, the anti-washout performance of the fiber silica fume cement grout under the low flow velocity was better than that of the pure cement grout, but the anti-washout performance of the fiber silica fume cement grout was still poor when the flow velocity became high. The results showed that the redispersible emulsion powder could significantly improve the anti-washout properties of the grout. Even at high flow velocity (0.6 m/s), the grout retention rate was still more than 60%. The results provide a reference for the prevention and treatment of water inrush hazards in tunnel and the choice of grouting.

Key words: tunnel engineering, dynamic water grouting, anti-washout property, treatment of water inrush, grout retention ratio