Floor heave patterns and mechanical characteristics of high-geostress tunnel invert

Floor heave of tunnel invert is a common structural failure pattern in high-geostress environments. It significantly affects track smoothness and thus threatens train safety. To reveal the failure behaviour of inverted arch floor heave under high geostress, physical model tests were performed. The concept of the uplift strength ratio (USR) was introduced to describe the relationship between horizontal load and floor heave load, and the impact of the USR on floor heave failure was examined. The results indicated that floor heave failure pattern of inverted arches in high-geostress tunnels manifests as a ‘W+L’-type composite failure. The failure process of inverted arch floor heave can be divided into three stages: stable resistance, cracking surge, and penetration failure. In this process, the ‘critical inflection point’ is an important factor affecting the inverted arch floor heave in high-geostress tunnels. Once the radial penetration of the inverted arch cracks occurs, the structure enters the penetration failure stage, where the arch foot cracks continue to develop radially under the external load until penetration is complete. The degree of inverted arch floor heave failure increases with a reduction in the USR. The recommended range for the USR is≥0.5. The outcomes of this study offer a theoretical foundation for the design and optimisation of inverted arches in tunnels.