## 5 Monitoring and Activation Law Analysis of the Fault Activation Slip
### Stress Analysis
#### 5.2.2 Analysis of Monitoring Results of the Borehole Stress Meter  
After the borehole stress meter is installed, the frequency value and the compressive stress in the borehole aperture direction can be read directly on the reader. According to the schematic diagram of the borehole stress meter installation in Figure 6, the stress measured by the borehole stress meter is the compressive stress in the direction of the borehole aperture; that is, the variation in the additional shear stress of the rock mass located on the hangingwall and footwall of the fault plane along the dip direction of the fault plane. The variation curves of the compressive stress with time at each measuring point are shown in Figures 17-19.  
1. As of 14 April 2015, the stress values of each measuring point used for monitoring fault F2 are as follows: Z11-2 is 16.50 MPa, Z12-2 is 17.96 MPa, Z13-1 is 19.04 MPa, and Z13-2 is 15.75 MPa. Due to the damage near the measuring point, the readings of Z11-1 and Z12-1 are those as of 14 July 2012. The stress values of each measuring point used for monitoring fault F3 are as follows: Z13-3 is 8.41 MPa, Z13-4 is 7.67 MPa, Z14-1 is 7.50 MPa, and Z14-2 is 6.95 MPa. The stress of each measuring point of fault F4 did not change greatly.
2. From the calculation results, it can be seen that, with the continuous deep mining, additional shear stress along the fault plane is generated in the surrounding rock of the hangingwall and football of fault F2 and fault F3 and increases gradually over time, while the stress of fault F4 changes little and is within the error range. Through data analysis, compared with the change in the additional shear stress of each measuring point in the hangingwall and football of the fault at the same time, it is found that the additional shear stress of the hangingwall of the fault is greater than that of the surrounding rock of the football of the fault, indicating that the existence of the fault has a certain barrier effect on the stress distribution. The change in the additional shear stress at the monitoring point on the west side of the fault is greater than that on the east side, indicating that the influence of mining on the west side of the fault is greater than that on the east side--the main reason for this is that the mining area in the west is closer to the fault.  
Figure 19: The stress–time curve of each measuring point of fault F4 monitored by the borehole stress meter.  
Figure 18: The stress–time curve of each measuring point of fault F3 monitored by the borehole stress meter.  
3. Comparing the bolt stress meter and borehole stress meter at the same monitoring position of fault F2, it can be found that the additional shear stress generated by the same monitoring position of the fault is greater than the additional tensile stress within the same time. 4. Comparing the monitoring time with an abrupt change in the stress value and the large blasting time of stop, it can be found that the stress value increases rapidly after the large blasting operation, indicating that the blasting operation has a certain influence on the additional shear stress along the dip direction of the fault plane.