Gas explosions are extremely harmful in coal mines,which can cause lots of deaths and injuries in a short time.Moreover,the blast wave will destroy the roadway and lead to damages or even collapses of the roadway system,which will trap the miners from escaping as a result.The collapse of the roadways will also block the miner’s escape channel,which brings great difficulties to the rescue.In this paper,the roadway damage mechanism under the coupling of the blast load and the ground stress was studied.A combination of theoretical analysis,experiment and numerical simulation was used to study the dynamic response and damage characteristics of the surrounding rock of roadway structures.The main findings are as follow:(1)The static and dynamic mechanical properties of coal and rock materials were studied,and the evolution laws and damage characteristics of cracks during compression were revealed.It is found that dynamic compression will appear obvious hysteresis in the springback stage of the curve comparing with static compression.The fracture morphology of limestone was radial failure,and the bituminous coal sample showed shear failure.In addition,the relationship between sample fracture scale distribution characteristics and impact load are studied.It is found that the characteristic distribution of the small-scale fragments is obviously increased with the increase of the impact load.(2)The stress evolution of the surrounding rock of the roadway under the coupling of the blast load and the high stress was revealed.It is found that stress curves of the surrounding rock of the roadway had multiple peaks under the coupling of the blast load and the high stress comparing with a shallow buried rock.There was a retention period in the stress curves of the corners of the roadway.The surrounding rock of the roadway suffered shock wave,compression wave and elastic wave in turn,which generated multiple stress peaks,negative pressure regions and stress oscillation,respectively.Besides,the retention period decreased with the increase of ground stress or even disappeared.(3)The damage mechanism of the surrounding rock under the coupling of the blast load and the ground stress is studied.The damage division method was proposed.We found that the damage zone of the surrounding rock had a trapezoidal shape as a result of the coupling of the blast load and the ground stress,which can be divided into three seperated zone: the complete damage zone,the plastic damage zone and the elastic damage zone.The surrounding rock expanded to the left and right in the horizontal direction,and exhibited upward and downward expansion deformation in the vertical direction under the coupling of the blast load and the ground stress,which eventually led to macroscopic damages in the corners of the roadway,while there was no obvious macroscopic damages in the two sides and the top floor of the roadway.(4)We found that the blast load could lead to a ground stress transient unloading.The coupling damage laws of the surrounding rock of the roadway was revealed.The transient unloading caused by the gas explosion mainly occurs in a small zone of the two sides,the bottom and the top of the roadway.The plastic damage zone of the surrounding rock of the roadway sides decreased with the increase of the lateral pressure coefficient.The research findings have academic and scientific significances for supplement of the damage mechanism of the coupling of the high ground stress,explosion load and transient unloading,and would contribute to anti-explosion design of roadway.In addition,2 related papers have been published(one indexed by SCI,the other indexed by EI). |