Study On Stability And Rockburst Prevention Technology Of Coal Pillar Of Island Coal Face Under Backfilling

In recent years,rockburst accidents in coal mines have been frequently occurring,and major coal mines are faced with the challenge of "three-under" pressure-coal problems.Backfill mining has a high level of safety and provides significant assistance in addressing these two issues.This thesis takes the C8301 island working face of the Yunhe coal mine as the research subject,and employs theoretical analysis,numerical simulation,and engineering practice to study various aspects,such as the reasonable width of the coal pillar in the island working face during backfill mining,the optimal backfilling rate,and the rockburst prevention practices in the island working face.The systematic research focuses on the stability of the coal pillar in the island working face and the prevention and control of rockburst during the mining process,and proposes a rockburst prevention and control scheme for the island working face.Combined with on-site data,the scheme has achieved good application results.The main conclusions of the thesis are as follows:(1)In the initial stage of mining in the C8301 backfill working face,the destruction of the overlying rock layer structure in the mined-out area leads to the direct roof collapse and subsidence.Subsequently,the compaction of the backfill causes further concentration of coal pillar stress,promoting compressive deformation,and making it highly susceptible to rockburst instability.The working face is located in a coal mine with a large mining depth,which bears a significant weight of the overlying rock layers.Considering the specific situation of the working face,the reasonable width of the coal pillar should not be less than 7.73 meters.(2)By using FLAC3 D numerical simulation and varying the coal pillar width and backfilling rate,the stability of the coal pillar during the mining process is analyzed.It is found that the peak stress within the coal pillar decreases with the increase of coal pillar width and the increase of the backfilling rate.When the coal pillar width changes,the stress concentration tends to stabilize after the coal pillar width reaches 8 meters.Under the condition of a fixed 8-meter coal pillar width,as the backfilling rate increases,the reasonable backfilling rate is determined to be 90%by analyzing the stress and plastic zone distribution within the coal pillar.(3)Based on the microseismic events and CT inversion results obtained from the field measurements during the mining process,it is concluded that there is still a risk of rockburst on the side of the coal pillar in the working face.It can be observed that the stress on the track side of the working face is greater than that on the belt side.During the mining process,microseismic events are mainly dominated by low-energy events,and most of the larger microseismic events occur within 20 meters above the coal seam.The frequency of microseismic events increases with the advancement of the working face,while the total energy and maximum energy decrease continuously.(4)In the actual production process of the C8301 working face,four measures are implemented for rockburst prevention and control: large-diameter drilling,coal body pressure relief blasting,high-pressure water injection pre-splitting for risk alleviation,and roof blasting.By analyzing the on-site stress monitoring data and drill cuttings method data,this rockburst prevention and control scheme has achieved good results in the field mining practice.