Numerical Investigation on the effect of the internal water pressure and leakage force on the behavior of tunnel lining

There is a pressure tunnel as the type of structures, which is mainly used in the hydroelectric power industry and in order to design and construct these structures, there are many engineering challenges. One of these problems is the leakage around the tunnel and, consequently, erosion caused by excessive water pressure, and it will lead to instability and the destruction of pressure tunnels. The main objective of this paper is to investigate and evaluate the numerical effect of internal pressure and the water leakage force simultaneously in the design of pressure tunnels. To accomplish this, water tunnels have been modeled and analyzed with different levels of groundwater and different overheads, under the influence of internal pressure using PLAXIS3D software and the finite elements method. The results indicate that due to the internal water pressure and the leakage force, by increasing the water level to tunnel overhead, the overall deformation of the tunnel has decreased and the incidence of stress has increased. Also, increasing the ratio of the depth of overhead to the diameter of the tunnel increases the amount of general and shear bends, and the axial and shear forces and the bending momentum on the tunnel cover decreases.