## 6 Conclusions  
Through a series of field and laboratory tests--including point load tests, triaxial tests, and loose circle tests--the fundamental physical and mechanical properties of steep  
Figure 35: Comparison diagram of tunnel inverted arch before and after renovation. surrounding rock are investigated. The study employs a custom-developed finite element method (FEM) integrated with the volume of fluid (VOF) approach to simulate both the failure of steep surrounding rock and the tunnel floor heave. This simulation facilitates an analysis of the progressive failure process and underlying mechanisms. Based on these findings, remediation measures are proposed and implemented as follows:  
(1) Relative to uniform surrounding rock, the failure zone in steeply inclined, thin-layered soft rock tunnels experiences accelerated deformation rates. This is particularly evident with high lateral pressure coefficients, where the initial failure zone expands rapidly, stabilizes within a certain range, and subsequently leads to gradual damage within the surrounding rock. (2) The surface deformation of the tunnel's sidewall correlates closely with the location of the failure zone within the surrounding rock, which can be inferred through surface displacement measurements. For instance, with a lateral pressure coefficient of 0.5, a 4 cm surface displacement corresponds to a failure zone beginning at 2 m. At 8 cm displacement, the failure zone extends to 5 m and stabilizes thereafter. During initial deformation stages, the failure circle expands rapidly; for example, at 3 cm surface deformation, the failure circle extends to 6 m, with subsequent slower changes. Comparative numerical simulations indicate that the tunnel floor heave is caused by steeply dipping thin surrounding rock. (3) The results of field tests and numerical simulations show that the key factors causing the floor heave of steeply inclined tunnels are the following: large buried range, no inverted arch structure, low angle of locking bolt, and insufficient design strength. Solving the shallow instability includes strengthening advanced support, controlling early surrounding rock deformation, lengthening the anchor rod, and adopting self-propelled anchor rod construction technology to ensure that the anchor rod can play an effective role. To improve the stiffness of the bottom structure, it is necessary to increase the inverted arch structure and adjust the angle of the bolt and improve its design strength. (4) Future research should focus on the following three areas:  
**Integration of Artificial Intelligence and Geomechanics Models:** Advancing the integration of artificial intelligence (AI) with geomechanics models is vital for developing more accurate and reliable prediction tools in tunnel engineering. Early implementation of AI-driven models for predicting large deformations in steep rock tunnel structures is essential for achieving successful applications. This integration promises to enhance prediction precision and operational effectiveness. **Large-Scale Model Tests:** Conducting large-scale model tests is necessary to understand the progressive failure mechanisms of tunnel inverts within steeply inclined thin rock masses. These tests, when combined with the mechanical models discussed in this paper, will provide valuable insights into the failure processes. This approach will elucidate the disaster mechanisms involved and improve our understanding of the conditions leading to structural failures. **Enhancing On-Site Monitoring and Classification Methods:** Ongoing on-site monitoring should be continued, and in combination with this study's findings, a refined classification and grading system for tunnel floor heave should be developed. **Author Contributions:** Conceptualization, R.F. and T.C. ; Methodology, R.F. ; Software, X.Y. ; Validation, R.F., T.C., X.Y., G.W., M.L. and S.W. ; Formal analysis, G.W. ; Writing--original draft, R.F. ; Writing--review & editing, T.C., X.Y., G.W. and M.L. ; Visualization, S.W. ; Supervision, T.C.