Optimization Of Section Coal Pillar Width On Full-mechanized Mining Face In Shallow Coal Seam

The research on the reasonable width of coal pillars in the shallow coal seam fully mechanized coal mining face is of great significance to the green mining of coal.Based on the 14204 fully mechanized coal face in Zhangjiamao Coal Mine,this paper optimizes the width of coal pillar by means of laboratory test,theoretical analysis,field monitoring,numerical simulation and industrial test.The main conclusions are:(1)Analyze the influencing factors and stability indexes of pillar coal pillars,sample from the site,conduct indoor tests,and obtain the physical and mechanical indexes of the coal samples.Through the triaxial compression test,the coal samples are deformed and destroyed under different confining pressures.Characteristics,characterized by acoustic emission energy and ringing counts,reflect the evolutionary process of cracks and fractures extending from coal to instability fracture of coal samples.(2)A monitoring plan for the mining of the 14204 working face was developed and a site monitoring study of the characteristics of the coal pillar was carried out.The monitoring results show that the surrounding rock in the trough is stable,the width of the plastic zone near the coal pillar near the mined-out zone is small,and there is little internal fracture,and the width of the existing coal pillar can be optimized.(3)Analyze the basic criteria for setting the width of coal pillars in shallow coal seams and the stress state of coal pillars in the mining process of fully mechanized coal mining.Reasonable assumptions are made based on the on-site mining conditions at both sides of coal pillars.Simplify,establish the calculation model of the plastic zone and elastic zone of the section pillars respectively,derive the calculation formula of the width of the pillars,and draw a conclusion that the reasonable width of the segment pillars is 17.5m.(4)Considering the effects of one-time mining and secondary mining,the vertical and horizontal stress distribution of coal pillars during coal mining in the five working conditions,and the convergence and plastic zone distribution of surrounding rock along the roadway are given.range.The results show that the reasonable width of the section coal pillars is 17.2m.Combined with the on-site mining conditions the theoretical calculation results,one hydraulic support can be removed and the width of the coal pillars can be optimized to 17.45m.Industrial trials verified the rationality of the optimized section pillar width,and the monitoring results showed that the width of the reserved pillar was reasonable.