| Deep tunnels are often used in high water level and rich water areas in construction of new railway and highway. Construction of tunnels takes drainage as a main measure to deal with the groundwater and without considering water pressure in lining design, but the large number and long-term drainage of groundwater is destructive to the original balance, caused serious environmental problems. Nowadays, the construction of tunnel should meet the requirement of surrounding environment, in other words, a principle of limited drainage on the basis of blocking water should be putting forward to maintain the water balance. How to determine the correct lining external water pressure is a key problem to tunnel design and construction under the conditions of safety and reliability without affect the environment.In this paper, the theory of groundwater seepage field analysis was adopted to study the external water pressure and its distribution laws, and the major conclusions were drawn as follows:â‘ The formulas of hydraulic pressure in lining, reinforced circle of rock-mass and surrounding rocks of the circular tunnels with reinforced circle are obtained based on polar coordinate seepage analytic principle, under assuming that there is a radial stable seepage in the lining, reinforced region and surrounding rocks.â‘¡The formulas as front were used to calculate the external water pressure of the Fangdoushan tunnel, the external hydraulic seepage pressure with nonlinearity on the lining is acquired, and it proves that the reinforced circle can decrease the external hydraulic seepage pressure on the lining.â‘¢The thermal and structural analysis function of ANSYS was used to simulate the Fangdoushan tunnel when there is a non-radial stable seepage flow with free surface in lining and surrounding rocks. Then, the saturation line of groundwater, the distribution of water-head, the change of seepage velocity in designated path, the seepage water pressure distribution, and the influence of seepage to the distribution of stress and displacement were obtained. |
