Support performance of functionally graded concrete lining

- Functionally gradient is introduced into support of circular underground space.
- Elasto-plastic analysis and model tests on two-layered circular lining are conducted.
- Functionally graded lining has higher bearing capacities than single-layered lining.

By inverse analysis, the concept of functionally gradient is introduced into thick-walled lining to improve its supporting performance. Analysis shows that an ideal functionally graded lining has a higher elastic limit than a conventional single-layered lining. The ideal functionally graded lining model requires that the Young's modulus of the material should monotonically increase with the increase radius, which cannot be achieved in a single-layered lining. A composite lining composing of multi layers that have different Young's modulus can approximately function as an ideal functionally graded lining. Such a two-layered lining was studied and was compared with a single-layered lining. The study involved elasto-plastic analysis and model testing. The elasto-plastic analysis shows that the elastic load bearing capacities of the ideal functionally graded lining and the two-layered functionally graded lining are higher than the traditional single-layered lining. The model test results confirmed the analytical conclusion.