Investigation on the mechanical behavior of the multiple‐layered lining structure of a water conveyance tunnel with high internal water pressure

Abstract

This paper investigates the mechanical characteristics of a multiple‐layered lining shield tunnel structure utilized in the Water Resources Allocation Project of the Pearl River Delta through theoretical analysis and model testing. The multiple‐layered lining structure consists of an exterior precast reinforced concrete segment lining, a middle layer of self‐compacting concrete (SCC), and an interior steel pipe. With emphasis laid upon lining interactions and the effect of different burial depths, with 16 m considered as the minimum burial depth and 40 m as the maximum burial depth, the structure's performance has been evaluated during the operation. During the operation, under increasing water pressure, axial pressure decreases while tension increases, with inner linings effectively bearing the load and protecting outer segments. Therefore, deformations change; outer linings undergo greater outward displacements and fewer inward displacements. With acoustic emission (AE) counts of 2286 and 2057, respectively, in the minimum depth (16 m) and the maximum depth (40 m) loading conditions, AE monitoring shows persistent micro‐cracking, but the structure is still elastic and safe under the designed pressure of 0.75 MPa. However, to optimize long‐term performance, further research is necessary to address possible cracking and expansion. The multiple‐layered lining technique is a promising substitute for conventional methods and proves to be efficient, economical, and suitable for tunnels with moderate to high internal water pressure.