## 5 Discussions  
It is believed that the main factors affecting the overall stability of the tunnel include the vertical displacement (settlement) of the road surface, the horizontal displacement of the tunnel wall, the stress distribution of the tunnel wall, the category of the surrounding rocks of the tunnel, the geological structure conditions, and the \"activation\" factors of the gouves. The residual settlement in the goaf in the study area was predicted and analyzed [33], and the deformation and displacement were forecasted. The stress distribution of the tunnel wall is caused by the large change in the deep bedrock marker deformation, the engineering geological stability of the study area was comprehensively analyzed and evaluated, and the stability of the tunnel was predicted and evaluated by considering the above factors. The recently related research on highway structures passing through coal mine goaves include the research on the coal goaf's impact on the route selection of Xuzhou Huancheng Expressway conducted by [PERSON] [2; 3] from the Southeast University, which focused on the relevant impacts of coal mine goaves on highway cutting and subgrades in southern China as well as the corresponding control measures. Most of the above-mentioned research is mainly based on qualitative analysis, and the deformation fortification level of the local structure is low. The assessment and analysis of this project adopted a combination of quantitative and qualitative evaluation methods, and the structures (medium-long highway tunnels) affected by the goaves of the coal mines are sensitive to deformation. In this study, due to the limited scope of the study area, the engineering mechanical deformation characteristics of the caving rock masses in the multi-layer goat were analyzed in the process of numerical simulation. Considering that there is little difference in the direct root lithology of the coal seam, the caving rock masses in the goat were defined as the caving engineering geological type, so as to comprehensively simulate the deformation on the tunnel floor caused by the influence of the multi-layered goat. In future studies, if there is a significant difference in the direct roof of the multi-layer goat and the engineering properties of the goat in each layer vary greatly, then the different fractured engineering geological types can be defined for numerical simulation analysis. In this study, bedrock monitoring targets and base rock observations were built for the roofs of different goaves in the same section. As of 9 March 2015, the bedrock markers' subsidence was more uniform compared with that of the reference points, and generally, the sediment was small in the southeast and large in the northwest. Despite the differences in the settlement of the goaves at different locations, the subsidence rates of the monitoring points at different depths in all groups are basically the same, and the residual settlement of the tunnel site is mainly derived from the goal of seam no. 15. The goat of seam no. 15, with features of great mining thickness, late mining, and deep burial, has a controlling effect on the settlement of the site, and the settlement of the above layers of goaves is basically \"absorbed\" by this layer. When the research scope is relatively large and the deformation characteristics of the goat of the lower layers are different in space, the layered goat monitoring system can predict the later overall deformation of the upper part according to the monitoring data of the lower part of the layer, to play an early warning role and forecast the occurrence of geological disasters. A comprehensive monitoring system was used in this study, including the subsidence deformation monitoring of multi-layer sublevel discontinuities, tunnel subsidence deformation monitoring, tunnel rock stress monitoring, and subsidence deformation monitoring of the upper mountain body, and certain improvements were made compared with other previous projects that adopted only a single ground deformation monitoring method.