## 5 Other Monitoring Analysis and Measurement Verification
### Field Measurement and Inspection of Coal Drilling Cuttings  
In order to test the correctness of the calculation model of lateral abutment pressure in the longwall stop, an experimental study on coal body stress detection was carried out in the belt transport down chute of the 1301 working face in July 2016; that is, drilling was carried out in the coal pillar area 80 m on both sides and in the 1301 working face near the belt transport down chute; the stress state of this area was tested. The site drilling construction parameters were as follows: the drilling hole was 1.2-1.5 m above the floor, constructed along the dip angle of the coal seam and perpendicular to the side (the east side is 4-6\({}^{\circ}\) lower, the west side is 4-6\({}^{\circ}\) upward), the hole depth was 60 m, and the hole diameter was \(\Phi\) 80 mm. Drilling construction was carried out from south to north in sequence, with a spacing of about 50 m. A total of 17 boreholes were drilled. Except for #7 and #10 boreholes drilled in the 1301 working face, the remaining boreholes #1-6, #8, #9, and #11-#17 were drilled in the 80-m coal pillar area, as shown in Figure 16. For the convenience of description, the boreholes are divided into two groups, of which boreholes #1-#6, #8, #9, and #11-#17 in the 80-m coal pillar area are Group A, and the boreholes #7 and #10 in the 1301 working face are Group B. According to the principle of the drilling cuttings method, there is a quantitative relationship between the quantity and particle size of pulverized coal discharged from the borehole, the relevant dynamic effects (such as the coal gun, the suction drill, and the sticking drill), and the stress state of the coal body. On this basis, in the test process, the coal particle size, the number of coal guns, the strength of coal guns, and the dynamic phenomenon during the drilling process are respectively counted with a unit depth of 5 m to judge and describe the current drilling depth. After the test, the data collected on the site were sorted and analyzed, and the relevant results are shown in Figure 16. The white, yellow and red areas in the figure represent the stress concentration status in the coal body, in which the white area shows no stress concentration, and the red area is the highly concentrated area. From an analysis of Figure 17, it can be seen that the boreholes of Group A in the coal pillar area are essentially in the original rock stress state within the range of 1-20 m, and there is no obvious stress concentration, which is related to the recent boreholes in this area. The 1301 belt in this area was drilled to a depth of 20 m along the inner and outer sides of the belt transport down chute for pressure relief, resulting in the transfer of stress load within 20 m, so a relative 20-m wide \"low-pressure zone\" appeared in the chart. The stress state in the coal body changes after the hole depth of 20 m. Take 1\(\mu\) drill hole as an example to illustrate that, with the increase in hole depth, the particle size of coal powder changes from powder to small particles, and large particles appear when the hole depth reaches 46 m. The number and strength of coal guns also gradually increase, accompanied by the strong phenomenon of suction drilling. It can be determined that there is still stress  
Figure 16: Construction scheme of coal body stress detection in the 80-m coal pillar area. concentration in the 80-m coal pillar outside the 1301 belt slot. That is, the range of the lateral abutment pressure in the 1300 goal is more than 80 m, which exceeds the width of the 80-m protective coal pillar and directly affects the adjacent 1301 working face. At the same time, the data of the Group B boreholes (7#-10# boreholes) were analyzed. Group B is located in the coal body of the 1301 working face. The analysis results show that the coal body within 60 m of the 1301 working face is still within the influence range of the lateral abutment pressure of the 1300 goal.