A Coupled Fluid-mechanical Study On Seepage Field Of Tunnels With High Hydraulic Pressue

In order to study the distribution rules of seepage field in the surrounding rock-mass of tunnels with high hydraulic pressure in Karst areas, a series of methods, such as theory analysis, numerical simulation, model test and site investigate, are introduced and applied in this paper. Many meaningful results have been obtained. Relying on Research topics named "Study on the hydraulic pressure characteristics loaded on the lining of Qiyueshan Tunnel", research work is carried out and the results are apllied in the project of Qiyueshan Tunnel. In this paper, the main work including :Firstly, it is proposed firstly that the formation of seepage fields can be divided into two stages, including steady and unsteady flow. In unsteady flow, the deformation of rock and re-distribution of seepage field Changes at the same time, and mutual impact takes place between each other. Coupled fluid-mechanical interaction has to be considered in this stage. However, the deformation of rock and re-distribution of seepage field will be steady and no change will occur in steady stage, mutual impact between each other can be neglected. Therefore, coupled fluid-mechanical interaction don't have to be taken into account.Secondly, based on the conformal mapping of complex function methods and " circular island model " for pumping wells thoery, the distribution rule of seepage field in homogeneous, isotropic medium is studied Systematically. A formula is given which is applied for the calculation of tunnel with high hydraulic pressure. Then, numerical simulation is carried out to Verify the correctness of the formula. Moreover, the formula applied for surrounding rock with adverse geological conditions is put forward.Thirdly, taking into account coupled fluid-mechanical interaction, the mathematical model for equivalent continuous medium is investigated. Then, the method to calculate the distribution of seepage field for the steady flow after coupled fluid-mechanical interaction.Fourthly, The seepage field and characteristics of structure under loads are studied through numerical simulation of both steady and unsteady flow. In the steady flow analysis, the relationship between the tunnel inflow and some parameters, including the thickness, the permeability coefficient of grouting and the discharge of tunnel, and the relationship curve between hydraulic pressure behind lining and discharge of tunnel is given. While in the unsteady flow analysis, some work is finished to research the laws of the distribution of seepage field, the deformation of stratum and characteristics of structure under loads, which is investigated through comparation of "Keeping up with the support" and "Support lagging". Fifthly, as a means, model test is carried out to research on the distribution of seepage field and deformation characteristics of structure under loads. The laws of distribution f hydraulic pressure is gained and the founction of grouting is proced. In the end, the test results are checked by numerical simulation.Finally, field test for the hydraulic pressure behind lining and tunnel inflow is executed in Qiyueshan tunnel. However, due to that the tunnel is still in construction, water pressure behind lining is still very small, it needs to be improved further.