Numerical analysis of segment linings in deep buried tunnels

Abstract

Deep buried hydraulic tunnels bear both external soil and water loads as well as internal water pressure during operation. Under high internal water pressure, the stress and deformation of their pipe structure are very complex. Relying on the Changhua River Water Resources Allocation Project in Hainan Province, the mechanical characteristics of the segment structure of high-pressure shield tunnels were explored from two perspectives: bearing different construction excavation loads and different segment assembly method. The results show:(1) The larger the excavation load borne by the pipe segment, the more obvious the “transverse elliptical” deformation of the pipe segment, and the more the circumferential stress distribution of the pipe segment tends towards a “necking” shape. The stress of circumferential bolts is related to the opening amount of pipe joints, and the distribution of pipe joint opening amount varies when bearing different construction excavation loads.(2) There is significant displacement and displacement between the staggered assembly structure rings, and the presence of longitudinal bolts and friction between the rings gives it a significant longitudinal strengthening effect.(3) Longitudinal bolts can share the stress state of circumferential bolts, and the stiffness of single ring pipe segments is significantly lower than that of multi ring pipe segments. It is recommended to use shear multi ring pipe segment structures in numerical simulations.(4) There is basically no interaction effect between the rings in the seamless structure pipe segments, and there is a process of internal force transmission in the staggered structure pipe segments, which decreases from the middle ring to both ends. Under the interaction force between the pipe segments and the action of longitudinal bolts, the stiffness of the middle ring pipe segments is improved.

Keywords

high water pressure / shield tunnel / excavation load / assembly method of pipe segments / deformation and stress