Load bearing and deformation characteristics of single-layer segment lining structure for water conveyance tunnels

The in-situ tests on the single-layer lining structure for water conveyance tunnels in South China are carried out, the mechanical response of the structure under the internal pressure in the surrounding rock is revealed, and the influences of different surrounding rock conditions on the load bearing and deformation characteristics of the single-layer segment lining structure are further studied by using a three-dimensional finite element model. The results show that under the internal pressure, the single-layer segment lining structure presents a "transverse ellipse" and expands outward, and the joint opening and bolt stress increase with the increase of the internal pressure. When the single-layer lining water conveyance tunnel is in class V surrounding rock, the convergence deformation of the linings and bolt stress should be combined to judge whether the structure reaches the normal service limit state. When it is in class IV surrounding rock, the bolt stress is the controlling factor for the structure to reach the normal service limit state. With the improvement of mechanical properties of the surrounding rock, the internal pressure-sharing effects of the surrounding rock are enhanced, which can improve the internal pressure bearing capacity of the structure. The difference of the internal and external pressures of the single-layer lining water conveyance tunnel in class V surrounding rock should not exceed 0.15 MPa, and that in class IV surrounding rock should not exceed 0.25 MPa.