## 4 Design and Stability Analysis of Surrounding Rock-Supporting Structure of Shaft
### Monitoring of Support Effect  
Measurement points were set to monitor the construction process and deformation of the surrounding rock and supporting structure of the horizontal section between shaft depths of \(-600\) and \(-700\) m. The accuracy requirement of shaft construction deformation monitoring is 1 mm, the distance between the deformation monitoring lines was set to 2 m, the two original plans and optimized support plan were monitored, and the shaft lining was  
Figure 13: Surrounding rock-supporting interaction curves.  
repaired after the original support structure was destroyed. Based on the above analysis regarding the cause of damage to the supporting structure, the height of the excavation section was reduced to 2 m during the repair process. The well wall destruction sites were eradicated and cleaned out before the initial supports with high-strength anchors, 40-50 mm thick concrete closures, and flat plutons were re-sprayed. A force of 150 kN was applied to the pre-anchoring force and the monitoring frequency was increased when the anchors were installed. The amount of rock deformation and the deformation rate were recorded, and the interaction law of the SCC and surrounding rock GRC calculated based on the strain-softening model was analyzed. Surrounding rock deformation of 100 mm is considered to apply the secondary support in a timely manner. A wooden wedge was driven between the well circle and surrounding rock to fasten the well circle. The concrete structure was poured for 6-8 h after the well circle was constructed. The concrete model was C35 grade and the jetting thickness was 700 mm.  
Figure 14 indicates that the original scheme did not meet the calculation results, and instead reached its support resistance limit value and was destroyed by day 20 after installation. The rock gradually destabilized after failure and its shape variable still showed no notable convergence trend after 300 mm. This support structure, therefore, cannot meet the rock stability control requirements. The original scheme 2 satisfies the calculation results of the ideal elastic-plastic model, but the support structure still produced failure. Furthermore, the failure time was delayed by approximately 5 days compared with the original scheme 1, the amount of rock deformation was large, and the convergence trend was still small. The support structure designed based on the strain-softening model fully considers the strain-softening characteristics of plutons, and the idea of high-resistance release pressure is introduced to rationally adopt the high-strength anchor as the initial support to release the rock stress. Both optimization schemes use well coils and sprayed concrete as secondary high-stiffness supports, and can ensure that the rock stability requirements are met. For optimization scheme 2, the rock deformation convergence rate was reduced to 1 mm/day by the 35 th day after setting the support structure. The surrounding rock deformation was then finally controlled at 140 mm and tended to be stable, thereby meeting the requirements for the surrounding rock stability.  
Figure 14: Timescale change of support structure convergence.