过空巷工作面超前煤柱渐进损伤破坏模式及其失稳机理OA

In order to explore the progressive damage failure mode and instability mechanism of the advanced coal pillar when the working face passes through the abandoned roadway,briquette specimens with width-to-height ratios of 0.50,0.75,1.00,1.50,and 2.00 were prepared for unilateral constrained compression tests,and acoustic emission(AE)monitoring was carried out simultaneously.The following research results were obtained.With the increase of width-to-height ratio,the compressive strength of the specimen decreases first and then increases,reaching the minimum value(9.28 MPa)at a width-to-height ratio of 1.00.The peak strain of the specimen increases linearly,while the elastic modulus decreases in a negative exponential trend.Besides,with the increase of the width-to-height ratio,the strengthening rates of the unilateral constraint on the strength and peak strain both rise linearly,the maximum values being 76.87％and 72.18％,respectively,while the strengthening rate of the elastic modulus falls linearly,the maximum value being 14.99％.The macroscopic cracks of the specimen mainly appear on the constraint surface.As the width-to-height ratio increases,the failure mode of the specimen gradually changes from single-slope shear failure to X-shaped conjugate shear failure.Under unilateral constraint,the proportion of shear fractures grows first and then declines,reaching the highest(53.43％)at a width-height ratio of 1.00.In contrast,under uniaxial conditions,it grows exponentially,and shear failure acts as the predominant failure mode.The damage constitutive model based on the strain equivalence principle and the compaction coefficient K can well reflect the damage and failure process of the advance coal pillar in a working face passing through the abandoned roadway.The research can provide reference for controlling the width-to-height ratio of coal pillars in the failure area of small kilns and for implementing backfill reinforcement measures.