# Coal and Gas Outburst Risk Prediction and Management Based on WOA-ELM
## 3 Gas Outburst Risk Prediction Index System  
According to the records in the gas outburst accident report, and from the perspective of gas outburst prevention and control work, the causes of gas outburst accidents are analyzed and, based on this, the gas outburst risk prediction index is constructed [2]. By analyzing the coal and gas outburst accident report from 2008 to 2021, the causes of the accident can be divided into unsafe conditions and unsafe behaviors. Unsafe conditions include coal characteristics, gas characteristics, and geological structure. Unsafe behaviors are analyzed from the perspective of gas outburst prevention. 1. Unsafe conditions
2. Gas pressure  
In coal seams, the occurrence mode of gas is divided into free state and adsorption state. The gas pressure of the coal body is related to the gas in these two modes of occurrence. Gas pressure characteristic is an important index for predicting coal and gas outburst, which determines the risk degree of coal and gas outburst, and its critical value is 0.74 MPa [34]. 2. Initial velocity of gas diffusion  
The initial velocity of gas diffusion is defined as the concentration of gas released from a coal seam. The initial velocity of gas diffusion is the difference between the amount of gas in the first 10 s and the last 15 s of the minute when the coal body starts to release gas. Therefore, the faster the initial velocity of gas diffusion, the greater the gas content of the coal seam and the greater the possibility of gas outburst. Accordingly, the amount of coal seam gas is positively correlated with the initial velocity of gas diffusion. Therefore, the initial velocity of gas diffusion is used as an indicator of gas outburst risk, and its critical value is 10 mL/s [34]. 3. Gas content  
The gas content is positively correlated with the risk of gas outburst, i.e., the higher the gas content in the coal seam, the greater the risk of gas outburst, with a critical value of 8 m\({}^{3}\)/t [34]. 4. Coal sturdiness factor  
The coal sturdiness factor can comprehensively reflect the coal's physical properties, such as strength, hardness, etc. The larger the value is, the better the physical properties such as strength and hardness of coal, which can resist more vital destructive force and is less likely to be damaged. The relationship between coal sturdiness factor and strength and hardness is a positive correlation, and its critical value is 0.5 [34]. 5. Porosity  
During gas outburst, the primary gas source is the pores or fractures of the coal body, and the amount of gas coming out from the coal seam is much larger than the amount of gas in the coal bed. The pore structure is divided into macroscopic and macroscopic, and both structures determine the mechanical properties of coal. The pore and geological structures are the root cause of gas outburst. 1. Unsafe behaviors  
According to the Regulations on Prevention and Control of Coal and Gas Outburst and Coal Mine Safety Regulations [35; 36], the coal and gas outburst prevention and control process can be divided into four stages, as shown in Figure 4. Ten workflows in these four stages may generate unsafe behaviors based on this analysis of 150 gas outburst accident reports from 2008 to 2021.