Crack propagation mechanism of inverted arches in large cross-section tunnels

Abstract

Floor heave-induced failure is a primary type of failure in the inverted arches of tunnels. In this study, the crack propagation behaviours in an inverted arch during floor heave were investigated using model testing and numerical simulations. In particular, the study analysed the effects of the thickness and curvature of the inverted arch on crack propagation. The analysis revealed that the centre and sidewalls of the inverted arch experience high contact pressures, while its feet experience bending shear and concentrations of stress. Tensile cracks first form at the centre of the arch, which then rupture the arch in the longitudinal and vertical directions to ultimately form a W-shaped failure mode. Furthermore, the centre and feet are the structural weak points of inverted arches. Increased arch thickness helps to reduce crack development but not linearly. Tensile crack development at the centre of the arch progressively weakens with increasing arch thickness. By contrast, crack development at the feet initially increases and then decreases with increasing arch thickness. Generally, crack growth in the inverted arch of a tunnel depends on its curvature. However, it does not progress monotonically; crack growth initially decreases, and then increases with increasing radius of curvature. The results of the study show that a rise-to-span ratio of 0.10 is optimal for crack resistance, as crack development is minimal at this ratio. In conclusion, we expect that the results of this study will inform the optimization and design of inverted arch structures.