Mechanism and Evolution Control of Wide Coal Pillar Bursts in Multithick Key Strata

Table 2

Statistical of representative rock burst of LW3102.

No.	Date	Energy (J)	Roof condition	Location	Damage length (m)	Damages of air-return roadway
1	2017.11.26	—	Periodic weighting	Coal pillar near goaf	25	The roof coal caved at the side of the coal pillar; the length, width, and height of the damaged area were 18 m, 1.5 m, and 0.6 m, respectively; in addition, the bolts and metal mesh failed
2	2017.12.13	—	Periodic weighting	Coal pillar near goaf	25	The roof subsidence was about 0.3–0.5 m; the floor heave was about 0.3–0.6 m; pillar walls were spalled; some hydraulic prop toppled
3	2017.12.25	—	Periodic weighting	Coal pillar near goaf	38	The roadway roof at the coal pillar side was inclined in the area 0–38 m ahead of LW3102; some wooden buttresses got damaged; tremors were felt
4	2018.1.26	—	Periodic weighting	Coal pillar near goaf	25	The roof subsidence was about 0.3–0.5 m; the floor heave was about 0.3–0.6 m, two walls spalled, and some hydraulic prop toppled in the 25 m ahead of LW3102
5	2018.3.3	6.4 × 10^6	Periodic weighting	Coal pillar near goaf	180	The floor heave was 1 m, with some hydraulic prop and wooden buttresses damaged in the 0–180 m ahead of LW3102; the ventilation of the air-return roadway was reduced from 2100 m^3/min to 1820 m^3/min due to deformation
6	2018.4.8	3 × 10^7	Periodic weighting	Coal pillar near goaf	300	The floor heave was about 1.2–1.3 m; the bolts and metal mesh were torn in the area 0–114 m ahead of LW3102; coal burst out in the area 45 m ahead LW3102