Deformation has been reported about underground structures in service caused by steel corrosion and external load due to ground subsidence. This research focused on the failure mode of deteriorated underground reinforced concrete (RC) structures with hollow circular cross-section. Small-scale structural experiments reproducing the effect of ground subsidence and steel corrosion were carried out, and shear failure on the side of RC specimens was clearly observed when the lateral earth pressure of surrounding ground was unequal. The experiments also showed that the loss of reinforcement plays a rather negative role to load carrying capacity of underground RC structures. Meanwhile, the FEM analysis considering the non-linear behaviors of both soil and RC was applied to compare and verify the experimental results.
In terms of the structural calculation for tunnel structures, flexural compression and axial compression are taken into account, while the possibility of shear failure is ignored. Unlike the flexural failure, there is a compression zone that can prevent underground water from flowing into the tunnel. Once the shear failure occurs at underground RC structures, the collapse of inner space and the immediate inflow of underground water are predicted. This research demonstrates the harmful impact on soundness due to steel corrosion and the necessity of paying attention to shear failure when designing underground RC structures with hollow circular cross-section.
