Study On The Impact Of Different Waterproof And Drainage Patterns Upon Water Pressure Load On Mountain Tunnel Lining

The groundwater problem of tunnel project come into being along with the tunnel project and always accompany the whole process of design, construction and operation. In a variety of complex or poor geological conditions, groundwater is one of the main which causes tunnel construction, normal operation and budget overruns. In order to deal with the groundwater problem economically and effectively, how to choose and combine waterproof and drainage patterns reasonable determine the success or failure of tunnel project. The requirement that tunnel adapts different geological and topographical conditions always changes, the idea of tunnel design always replaces, and the usage of waterproof and drainage patterns always affects the design of lining.This thesis studies systematic on the impact of different waterproof and drainage patterns upon the value and distribution of water pressure which loads on mountain tunnel lining. The main content as follows:(1) Aim at the determination of the water pressure upon the tunnel lining in jointed rock mass. According to the seepage theory, the equations for calculating seepage force in rock mass/lining are obtained, and the formulas of water inflow of tunnel are deducted as well. Based on axisymmetric solution, through integrating seepage force of lining, the equations for pore water pressure and the reduction factor of lining water pressure are obtained. By analysis of sensitivity the reduction factor of lining water pressuere, the main factor determining the reduction factor of lining water pressure is the relatively permeability of lining to rock mass is obtained. And controlling water inflow of tunnel is the main role of grout ring.(2) Using3D model test method to investigate the rule of hydraulic pressure distribution variations in the process of construction in different water level and permeable boundary conditions, centering on the water pressure at the whole drainage and full closure conditions. And the change of seepage is analyzed as well. The results show that the heterogeneity of fracture systems and instability of groundwater have a great impact on water pressuere load on lining.(3) Using numerical method, which based on3D model test, to analytically formulate the water pressure at outer surface of grout ring and lining back in case of mountain tunnel waterproof and drainage style, and to analyze the relationship between water pressure and other variables at lining back. And the relationship between the discharge capacity of the drainage and coefficient of water perssuer action is also obtained.(4) Using numerical method to study the effect of supportings and waterproof and drainage patterns on the groundwater potential and the distribution of water pressure of composite lining with waterproofing sheet and drainage system. The distribution of lining water pressure for different drainage style is discussed to provide the base for choosing suitable drainage system. And the relationship between waterproof and drainage patterns and water pressure load on lining is obtained.