Research on full-life cycle gas treatment technology based on floor rock roadway

For mines lacking conditions for mining protective layers, pre extraction of coal seam gas from floor rock roadway strips is the mainstream gas control method. The analysis indicates that there are problems in the practical application of the floor rock roadway, such as significant differences in the selection of spatial layers, poor stability of the surrounding rock of the coal roadway caused by through layer punching, high excavation cost, and low utilization efficiency. Based on the floor rock roadway and considering the gas problem throughout the entire coal production process, a full-life cycle gas treatment technology based on floor rock roadway is proposed. It forms a five-in-one gas comprehensive treatment model of "layer optimization, through layer punching, layer grouting, mining extraction, and gangue backfill". Taking Shoushan No.1 Coal Mine as an example, by measuring the rock mechanics properties of the strata in the coal mining face, the stability of the floor rock roadway under the conditions of roadway excavation and mining face is analyzed based on the numerical method. Based on the characteristics of surrounding rock damage and the distribution of stress in the mining surrounding rock, it has been determined to arrange the bottom rock roadway at a position of 16 meters below the mining face transportation roadway and 1 meter inboard from the upper transportation roadway. The layout of hydraulic punching holes in the floor rock roadway is optimized. The group spacing is set to be 6.4 meters. The interleaving drilling is arranged by odd and even numbers for each group. By measuring the residual gas pressure of hydraulic punching holes, it is found that the effective influence range of hydraulic punching holes exceeds 4 meters. The hole gas concentration is high and the decline is slow. The strip pre-extraction effect is good. The though layer grouting technology is used to improve the properties of the upper broken coal body. The drilling observations show that the strength of the coal body after through layer grouting reinforcement is increased and the degree of fragmentation is decreased. The monitoring results of the deformation of the roadway side show that the overall stability of the surrounding rock of the roadway is good. The strength of the coal seam is increased. The monitoring results of the amount of drilling debris show that the grouting reinforcement range exceeds 5 meters, effectively reducing the risk of outburst in the roadway excavation. Through drilling through the floor rock roadway, the pressure relief gas extracted during the mining process of the working face is extracted. It is found that the effective influence range of mining is 50 meters in front of the coal working face. The gas extraction effect in the mining-affected area is good. The gas concentration in the air flow of the coal working face is reduced to below 0.45%, effectively reducing the gas concentration in the coal mining face. After the completion of mining, a method of backfill gangue in the floor rock roadway is designed to reduce the cost of gangue extraction and improve the utilization efficiency of the roadway.