A METHOD TO PREDICT THE RELATIONSHIP BETWEEN WATER DISCHARGE AND PRESSURE DURING OPERATIONAL PERIOD OF CITY TUNNELS CONSTRUCTED USING THE MINING METHOD

To predict the relationships between water discharge and secondary lining external water pressure over the operational phase is a key issue in tunnel design. Differences in the reach of the seepage field of tunnels subject to high and low water levels requires the consideration of boundary effects when theoretically predicting the water discharge-pressure relationship. This study analyzed water discharge during tunnel operational stage and the secondary lining external water pressure of tunnels subject to high and low water levels, employing the groundwater seepage theory, the complex conformal mapping theory, and the complex two-dimensional steady flow theory combined with the refined model of surrounding rock-supporting structure and the meteorological factors. Based on the being constructed connecting line project of Shenzhen Eastern Transit expressway, the relationship between water discharge and pressure of city tunnels was investigated considering various permeability coefficients and thickness of the grouting circle. The results show that the secondary lining external water pressure reduces linearly as the tunnel water discharge increases, regardless of what the water level is. The effect of the variation in permeability on reducing water pressure due to water discharge appears to be more prominent than the variation in the thickness of the grouting circle. With the same increase or decrease proportion of permeability coefficient of the grouting circle, the reduction rate of water pressure-discharge of city tunnels with low water level is faster, whereas with the same change in the thickness of the grouting circle, the reduction rates of water pressure-discharge of city tunnels of both high and low water levels are almost the same.