Abstract:

In the aim of exploring the mechanical actions underlying the joint bearing of surrounding rock and stacked lining structure in cirlular hydraulic tunnel, this study focuses on the three-layer stacked lining used in the Pearl River Delta Water Resource Allocation Project. The lining structure comprises an outer concrete segment, a self-compacting concrete filling layer (SCC), and an inner steel tube. Using the power series solution of plane elastic complex function theory and stress function analysis, we established a mechanical model considering the interaction between surrounding rock and lining as well as stress boundary conditions. We derived and solved the stress components at any point within the surrounding rock and each layer of the lining under combined excavation load and internal hydraulic pressure. This approach elucidates the load transfer mechanisms and behaviors of the stacked lining structure. We verified the accuracy of our method by comparing boundary stress results with numerical simulations. Finally, through parameter analysis, we examined how increased internal hydraulic pressure affects radial and circumferential normal stresses in the surrounding rock and the three-layer lining. Results manifest that when the surrounding rock and the three-layer lining work together to bear loads, both the radial and circumferential normal stresses exhibit a cosine distribution, while the shear stress follows a sine distribution. As the water pressure inside the water conveyance tunnel increases, the three-layer lining and surrounding rock become increasingly compressed in the radial direction, while the circumferential normal stress tends to become tensile and increases. The research findings provide a theoretical foundation for the design and construction of multi-layer lining systems in hydraulic tunnels.

Key words: circular water conveyance tunnel, three-layer linings, high inner hydraulic pressure, analytical method, load transfer mechanism