In-situ tests and numerical analysis of composite lining structures with joint bearing

An in-situ test on composite linings is carried out to investigate the characteristics of joint bearing performance under internal pressure. Based on the three-dimensional finite element refinement model, the process of structural failure and the deformation of the structures under various surrounding rock strengths are analyzed. The results show that the combination of rubber bladder and steel reaction frame provides a good simulation of internal water pressure in large-diameter section. The optical fiber sensing technology enables continuous monitoring of tunnel structures at full cross-section. The joint bearing effects of the composite linings are obvious, and the structures show a tendency of "transverse ellipse" with outward expansion and tension under internal pressure. The concrete cracking of the inner linings is the controlling factor for the decrease of structural bearing capacity. The structures reach normal use limit state and the joint bearing performance decreases when the difference of the internal and external pressures exceeds 0.40 MPa. As the strength of surrounding rock increases, the deformation and internal force response of the structures decrease, and the effects of surrounding rock to share the internal water pressure are enhanced, so the thickness of the linings can be appropriately optimized.