Research On Optimization Of Coal Pillars In Section Of Fully Mechanized Mining Face In Near Shallow Buried Thick Bedrock "Three Hard" Coal Seams

Sectional coal pillars are used as roadway protection coal pillars in fully mechanized mining face.During the process of roadway protection,they will be affected by multiple mining operations.If the coal pillar size is too small,it will not only fail to protect the roadway,but will also lead to goafs.Disasters such as gas outburst caused by gas exchange with the working face;if the size of the coal pillar is too large,it will not only cause waste of resources,but may also induce dynamic disasters such as roof accidents.Therefore,the paper combines indoor experiments,field measurements,theoretical analysis,simulation experiments and other methods to study the reasonable size of coal pillars in the section of Xuemiaotan Coal Mine.The main research results are as follows:(1)Based on the occurrence conditions of the coal seams with shallow burial,thick bedrock,and base-load ratio greater than 1,the mechanical characteristics of the 3#coal seam and the roof and floor have been tested to obtain the hardness characteristics of the three,which are judged to be near shallow burial."Three hard" coal seams.(2)Through on-site mine pressure monitoring,it is concluded that when the working face is compressed,the resistance concentration of the hydraulic support and the strength of the pressure are small(the maximum strength of the pressure is 1.14),the stress and internal deformation of the coal pillar are small;the surrounding rock is loosened The circle test shows that the maximum loose circle of the coal pillar is 0.8m;based on the SMP criterion,it is calculated that the ranges of the coal pillar goaf and the plastic zone on both sides of the roadway are 3.18m and 0.31m respectively,and the section coal pillar width is calculated to be 9.84 m.(3)Analyze the stability of coal pillars of different sizes through numerical simulation and similar simulation experiments.The results show that the width of the coal pillar is within the range of 12m?20m,the plastic zone and failure deformation of the coal pillar are similar,and the stability of the coal pillar is good,in the range of 8m?12m.The inner coal pillar can still meet the conditions of roadway protection.If it is less than 8m,the supporting effect of the coal pillar will be worse.(4)Considering the above research comprehensively,the coal pillar width of the 3#coal seam section of Xuemiaotan Coal Mine is optimized from 19.2m to 10m.The research results of coal pillar stability in the "three-hard" coal seam section in this paper can not only create good economic benefits for Xuemiaotan coal mine,but also provide theoretical basis for coal pillar retention in similar mines.