## 6 Engineering Applications
### Monitoring Method of Tunnel Convergence Deformation and Setting of Measuring Point  
Roadway surface displacement is the most direct basis for the evaluation of the roadway supporting effect and surrounding rock stability, and its monitoring content includes the displacement of two sides and the displacement of the top and bottom. According to the monitoring results, the improved support effect and deformation rule of surrounding rock can be judged, and the feasibility of support can be verified. The convergence deformation of surrounding rock on the roadway surface was monitored using the cross-distribution method, as shown in Figure 12.  
Figure 11: Support program diagram.  
Figure 13 shows that in the initial stage of measuring point arrangement, the coupling between the supporting system and surrounding rock is weak, supporting bodies such as the anchor net have not fully played their roles, and the deformation rate of the roadway is fast. With the increase in roadway deformation, the coupling between roadway surrounding rock and the supporting system was greatly enhanced on the 10 th to 15 th days, and the roadway deformation rate slowed down significantly. After the 15 th day, the roadway deformation rate tended to be stable.  
Figure 12: Distribution diagram of key points in roadway section.  
Figure 13: Tunnel convergence deformation monitoring. (**a**) Roof-to-floor convergence, (**b**) two sides move closer.  
Through field monitoring, the displacement value of the surrounding rock of the roadway measuring station can be obtained, and then the stability of the roadway can be evaluated using the convergence rate, as shown in Table 6. Based on the empirical value summarized from long-term engineering practice, when the relative convergence rate of the largest two sides and roof and floor of the roadway does not exceed 2%, the roadway is judged to be in a stable state, indicating that the roadway supporting parameters are feasible.  
As can be seen from Table 6, the relative convergence rates of the top and bottom plates and the two sides of the measuring points are 1.66% and 1.82%, respectively, both of which are less than 2% and within the allowable convergence rate range. Therefore, the roadway is judged to be in a stable state. It shows that the roadway supporting parameters are feasible and can provide reference for similar roadway supporting.  
After determining the parameters of anchor net spraying support and implementing the engineering application in Makeng Iron Mine, under the influence of the vibration of deep hole blasting in the quarry, the sprayed concrete layer close to the blasting point will be cracked, but no spalling phenomenon will occur. Due to the blasting disturbance, the service life of the roadway near the blasting point supported by sewing pipe-type anchor net spraying is relatively short. In order to improve this situation, the mine adopts the method of filling after the stage mining room and follows the principle of \"quick mining, quick exit, quick filling\" for the management of the quarry. By filling the hollow area in time, it effectively reduces the deformation and displacement of surrounding rocks around the hollow area, inhibits the further expansion of cracks in the shotcrete layer, and, thus, avoids the occurrence of concrete layer spalling. After the filling is completed, only the local cracked area needs to be shotcrete repaired to restore its integrity and ensure the long-term stability of the supporting structure. Practice shows that this method can significantly improve the stability of the roadway surrounding rock, providing a strong guarantee for the safe production of the mine.