## 5 Monitoring and Activation Law Analysis of the Fault Activation Slip
### Stress Analysis  
#### 5.2.1 Analysis of Monitoring Results of the Bolt Stress Meter  
(1) Computing formula  
In the measurement process of the bolt stress meter, the stress of the surrounding rock around the final fault can be calculated by Formula (2) [35].  
\[P=\frac{P^{\prime}}{A}=\frac{S*\left(f_{i}^{2}-{F_{0}}^{2}\right)}{A} \tag{2}\]  
In the above formula:  
\(P\)--Stress on the measured bolt stress meter (MPa);  
\(A\)--Cross-sectional area of the measured bolt stress meter (m\({}^{2}\));  
\(P^{\prime}\)--The force on the measured bolt stress meter (kN);  
\(S\)--Sensitivity coefficient of the bolt stress meter (kN/Hz\({}^{2}\));  
\(F_{0}\)--Initial frequency of the bolt stress meter;  
\(f_{i}\)--Working frequency of the bolt stress meter.  
(2) Analysis of monitoring results of the bolt stress meter  
If the frequency of the bolt stress meter reading instrument increases, the calculated results are positive under tension force. The frequency of the readout is decreased, and the  
Figure 12: Multipoint displacement meter monitoring displacement–time curve of each measurement point of fault F3.  
Figure 13: Multipoint displacement meter monitoring displacement–time curve of each measurement point of fault F4.  
1. As of 14 April 2015, the stress values of each measuring point used to monitor fault F2 are as follows: M11-2 is 9.77 MPa, M12-2 is10.20 MPa, M13-1 is 11.24 MPa, and M13-2 is 11.44 MPa. Due to the damage near measuring points M11-1 and M12-1, the readings of these two measuring points are those as of 14 July 2012. During the monitoring period, the average tensile stress of the hangingwall of fault F2 perpendicular to fault plane 2 m is 6.65 MPa, and the average tensile stress of the football of fault F2 perpendicular to fault plane 2 m is 5.46 MPa. The stress values of each measuring point for monitoring fault F3 are: M13-3 is 3.64 MPa, M13-4 is 3.72 MPa, M14-1 is 4.27 MPa, and M14-2 is 3.96 MPa. The stress of each measuring point of fault F4 is within the initial error range, and the change is small.
2. The calculation shows that, with the continuous deep mining, the additional tensile stress of the surrounding rock of the hangingwall and footwall of faults F2 and F3 is vertical to the fault plane and increases over time; the stress of fault F4 changes little. Through data analysis and the comparison of the changes in the additional tensile stress of each measuring point on the hangingwall and footwall of the fault at the same time, it is found that the additional tensile stress in the hangingwall of the fault is greater than that in the footwall of the fault at the same fault, indicating that the existence of the fault has a certain barrier effect on the stress distribution.
3. Comparing the three monitoring times with large stress variation values and the large blasting time of the stope, after the large blasting operation was carried out in the stope of sublevel 15 of the footwall of the main orebody, the stress value increases rapidly, indicating that the blasting operation has a great influence on the stress distribution in the fault and surrounding rock. It also indicates that the stress in the orebody and surrounding rock change significantly under the influence of mining, and the ground pressure activity enhances significantly.