Analysis of Non-Darcy Seepage Field and Stress Field of Surrounding Rock Strengthened by Grouting in Deep Buried Tunnel

Non-Darcy seepage with high velocity exists in deep buried tunnel engineering, particularly under high hydraulic pressure conditions. Grouting reinforcement is an essential form of support in the new Austrian tunneling method. Thus, non-Darcy seepage and grouting reinforcement should be considered as key factors influencing the seepage field and stress field of the surrounding rock. Therefore, an analytical model including grouted surrounding rock in non-Darcy seepage was proposed. The characteristics of non-Darcy seepage were illustrated and compared with those of the Darcy seepage, and the validity of the analytical solution was verified. The influence of the non-Darcy seepage and grouting reinforcement on the surrounding rock can be summarized as follows: the range of influence of non-Darcy seepage from the tunneling radius reaches three times the grouting radius. The effective stress of grouted rock is larger with non-Darcy law, particularly the hoop effective stress; the mechanical and permeability characteristics of the surrounding rock change after grouting, thus, the hoop effective stress increases rapidly towards the tunnel. After the grouting reinforcement, the effective stress of the grouted surrounding rock increases with an increase in the elastic modulus and decreases with a decrease in the permeability coefficient; in the tunnel grouting design with strict drainage control, the permeability coefficient should be reduced first, and then the grouting scope should be appropriately increased. The above conclusions provide a theoretical basis for the grouting design of deep buried tunnels under high hydraulic pressure conditions. © 2020, Editorial Department of China Journal of Highway and Transport. All right reserved.