## 5 Field Monitoring and Analysis
### Deformation Analysis of the Surrounding Rock along the Empty Excavation Alley  
The cross-point method [22] is used to monitor the amount of surrounding rock in the 130,205 ventilation return lane. The equipment used is a mining intrinsically safe laser distance meter, which automatically transmits measurement data to the surface via the internet. The measurement frequency ranges from 10 to 50 times per second due to environmental influences underground. The roadway section is divided into four sections for measurement, and five groups of surrounding rock deformation observation stations are set up in the 130,205 ventilation return lane. The deformation characteristics are analyzed by comparing the statistical data for each time.  
The data monitoring of return air began on 24 February 2019, and according to the design requirements, the relevant data were collected regularly, and the relationship between the distance from the observation point and the working surface distance was drawn on the observation section 100 m and 150 m from the open eye of the working surface (see Figures 9 and 10).  
Figure 9: Deformation map of the surrounding rock of the 130,205 ventilation return lane 100 m from the open cut eye.  
Combined with the location, it was found that the support drum on the side of the 5 m coal column in the goat area was larger than that at other positions in the roadway, which was the reason why the roof plate pressed the 5 m coal column and protruded backward to the goat area. The roof plate of the goat area behind the working surface is fully dropped, the overall cutting of the top beam of the bracket is good, and there is no bracket crushing phenomenon.  
Based on the deformation analysis of the surrounding rock of the roadway in area 130,205, the following characteristics of the ore pressure of the ventilation return lane are presented.  
1. First item:  
Within the range of 0 to 25 m ahead of the working surface, the roadway deformation is significant, and under the influence of the advanced support pressure, the gravity of the overlying rock layer is applied to the two vertical supports and transmitted to the bottom plate of the roadway, causing the supports and the bottom plate to bulge. According to the monitoring of the advanced support pressure of the working surface, the roadway within 50 to 70 m of the working surface is affected by the advanced support pressure, the plastic area of the roadway within 20 to 30 m of the working surface is obvious, and the mineral pressure is obvious.  
2. Second item:  
The two gangs of the roadway showed asymmetrical displacement, the surrounding rock on the solid coal side was significantly greater than that of the 5 m coal column side, and the coal body collapsed. Due to the influence of the mine pressure distribution, the solid coal side is closer to the peak of the advanced support pressure of the working surface and the stress in the coal body is larger, resulting in the deformation of the solid coal-side alley gang being larger, and the local help drum appears. While the 5 m coal column side is far from the peak of the support pressure and is in a stable internal stress field, the 5 m coal column has been grouted and anchored, and its mechanical properties are enhanced, so the deformation is small, and the strength of the mine pressure is not obvious.