Study On The Evolution Of Seepage Field And The Waterproof And Drainage Of The Urban Mined Tunnel

Based on the connecting line project of Shenzhen eastern border crossing expressway,this paper has selected several typical tunnel sections as the objects to analyze the evolution of seepage field of the urban mined tunnel, the prediction of tunnel water inflow, the affected scope of tunnel seepage field, the relationship between water pressure and displacement of tunnel and other related issues form the construction to the operation period. The theoretical analysis, field test, numerical simulation, laboratory model test and other methods are applied. The main research results are as follows :(1) The influence of each excavation step on the surrounding rock-support system in the construction of CD method is studied through the numerical simulation of fluid-structure interaction. The stress, displacement and water pressure distribution of surrounding rock and initial support are revealed. The affected scope of tunnel excavation under the conditions of different groundwater heads and surrounding rock permeability coefficients is verified.(2) A new similar material and its raw material ratio for surrounding rock, grouting circle and initial lining, etc, have been applied in mined tunnel seepage model test. Without considering the influence of excavation disturbance on the construction of the tunnel, the water inflow under different grouting circles and initial lining permeability coefficients is obtained by the self-developed seepage model test system for mined tunnel during construction and operation period. The numerical modeling and analysis are realized by the Visual-modflow software. The influence of grouting circle and initial lining permeability coefficient on water inflow during construction period is discussed. The results reveal the evolution of tunnel seepage field.(3) Considering the complete waterproof and drainage system of the tunnel, a theoretical formula of seepage field is derived. The effect of variable factors such as the grouting radius, the permeability coefficients of grouting circle and lining is explored. The effect of dynamic and static water head of different heights on water pressure,water discharge and the tunnel seepage field is analyzed. Based on the laboratory seepage model test, the variation characteristics of water pressure during the construction and operation period is studied considering different permeability coefficients of grouting circles. In special hydrogeological conditions (pass through the fault belt, undercross the spillway and so on), the evolution of seepage field before and after grouting is analyzed through the numerical simulation.(4) For the tunnel under different water levels during the operation period, a theoretical model of water discharge and external water pressure of secondary lining is applied to evaluate the effect of adjusting the external water pressure of secondary lining by controlling the tunnel drainage. The relationship between water discharge and water pressure obtained by the finite element analysis is reviewed by the laboratory model test.The research results of this paper have significant guiding function and practical meaning on the safety of the engineering. It could be extended to the design and construction of groundwater-controlled mined urban tunnels and provide theoretical and practical basis for development of norms in the future. It also could save investment for the country. The social benefit and economic benefit are remarkable.