Study on the influence of reserved coal pillar shape on the stability of coal mine working face

FENG Panfei; LIU Xudong; ZHANG Wenhai; PAN Pengzhi; ZHU Hongwei; WANG Zhaofeng

doi:10.16186/j.cnki.1673-9787.2022110019

Abstract：In the process of coal mining,it is often necessary to reserve coal pillars as load-bearing columns to support the gravity of the upper rock mass.Due to the different width-height ratios of the reserved coal pillars on site,it has a great impact on the stability of the coal mine working face.Through uniaxial compression numeri-cal tests conducted under different diametral-height ratios of coal rocks and their assemblages,the mechani-cal properties and fracture process of coal rock and its mass under different diameter-height ratios were ana-lyzed to investigate the influence of reserved coal pillars and their mass on the stability of the working face.The results showed that:(1)As the ratio of diameter to height increased gradually,the peak strength of coal rock and its mass increased synchronously.The coal rock changed from brittle to ductile,and then from duc-tile to brittle,and the mass rock changed from brittle failure to ductile failure,with the ductility of the mass de-creasing gradually with the continuous increase of the ratio of diameter to height.(2)With the gradual in-crease of the diameter to height ratio,the coal rock and its mass were mainly subjected to split failure,and the expansion direction of the crack failure is constantly changing dynamically,and the basic coal rock of the mass being broken by splitting failure.(3)The difference in peak strength between mass mass and coal rock was larger with the gradual increase of diameter to height ratio.The peak axial strain of coal rock showed no significant change with the increase of diameter to height ratio.The general trend of peak axial strain of mass mass increased with the increase of diameter to height ratio to a certain extent,and the peak axial strain of mass mass was higher when D/L=0.8.