## 7 Conclusions  
This paper conducts extensive investigation on the engineering issue of tunnel floor heave, identifying gently inclined thin-layered rock masses as the primary cause of this phenomenon. Through a combination of a theoretical analysis, numerical simulation, and field testing based on actual project conditions, this study systematically examines the influencing factors, mechanical models, and deformation mechanisms involved in tunnel floor heave. Additionally, an intelligent prediction method tailored for gently inclined thin-layered rock mass conditions is developed. The primary conclusions are as follows:  
1. Through an extensive investigation and statistical analysis, it has been observed that tunnel floor heave deformation is significantly influenced by the interplay of multiple fields, particularly the stress and seepage fields. This phenomenon is prevalent in both railway tunnels during construction and operational phases, especially when the surrounding rock consists of gently inclined, thin-layered formations. The effective ness of repair measures in such conditions remains unsatisfactory, indicating a need for further study and improvement. 2. Based on comprehensive field monitoring and numerical simulations, an analysis of the engineering characteristics of gently inclined, thin-layered rock masses was conducted. Through both single-factor and multi-factor analyses, six primary factors influencing floor heave in tunnels with such surrounding rock were identified: the lateral pressure coefficient, rock layer dip angle, hard rock layer thickness, thin layer thickness, elastic modulus of surrounding rock, and tunnel burial depth. The ranking of these factors in order of importance is as follows: tunnel burial depth > lateral pressure coefficient > thin layer thickness > surrounding rock elastic modulus > rock layer dip angle > hard rock layer thickness. A further analysis of the support system's mechanical behavior revealed that tunnel floor heave predominantly occurs in tunnels with grade III and IV surrounding rock. In contrast, tunnels with grade V surrounding rock experience subsidence at the floor due to the combined effects of high ground stress, tectonic stress, deviatoric stress, and the timing of support application. Compared to primary support structures, the combination of primary support and secondary lining can more effectively mitigate tunnel floor heave. 3. Grounded in the theory of a tunnel circumcircle and the principles of active and passive pressures in rock and soil, this study examines the structure and long-term stability of tunnel floors. This research uncovers the deformation mechanisms and ultimate bearing capacity of tunnel floors under the conditions of gently inclined, thin-layered stratification. Additionally, using the Nishihara model, a novel creep constitutive equation has been developed to elucidate the dynamic interaction between the tunnel floor structure and the surrounding rock support forces. 4. A formula for estimating tunnel floor heave was developed using a combination of on-site monitoring, statistical analysis, numerical simulation, and BP neural network techniques. After refinement, the formula achieved a coefficient of determination (R\({}^{2}\)) of 0.95, closely aligning with actual values. This formula is capable of not only estimating the extent of tunnel floor heave but also inverting the load at the tunnel base. Additionally, an intelligent prediction model for tunnel floor heave was established using the BP neural network algorithm. Following 100,000 training iterations, the loss function value reached 0.17, enabling highly accurate predictions of tunnel floor deformation. This research has been successfully applied and promoted in practical engineering, offering a robust theoretical foundation and technical support for future tunnel construction projects. 5.