Structural behavior of segmental tunnel linings for a large stormwater storage tunnel: Insight from full-scale loading tests

The deeply-buried tunnels serve as an effective method for the sustainable management of stormwater to mitigate the waterlogging and sewer overflow problems of modern cities in rainy seasons. This paper presents a series of full-scale structural loading tests on the segmental lining of a large deeply-buried stormwater storage tunnel considering the operation conditions, in which the cycle of water inflow and drainage was repeated. The testing results show that water inflow has notable influences on the mechanical and structural behaviors of segmental lining. The bending moment increases slightly but the axial force decreases significantly with the increasing inner hydrostatic water head. The convergence deformation develops during water inflow and recovers in the process of drainage, following a parabola pattern. However, the deformation cannot be fully recovered after complete drainage, mostly due to the residual deformation of segmental joints. The structural responses of the segmental lining remain approximately constant subjected to a limited number of loading cycles. The effects of water inflow on the distribution of internal forces and deformation deviate from the elastic solutions for homogeneous ring subjected to isotropic inner pressure. The influences of bending moment and axial force on joint behavior are unified through eccentricity. Three distinct zones associated with the interaction condition between adjacent blocks at the joint are identified for the relationship between joint deformation and eccentricity, and also for the relationship between joint rotational stiffness and eccentricity. The observations made in the current study may shed light on the design and construction of similar projects in pilot cities committed for the Sponge City policy of China.