Research On Dynamic Rebound Mechanism Of Roadway Roof And Its Influence On Instability And Failure Law Of Surrounding Rock

After the roadway is excavated,the coal body and roof of the roadway are subjected to a high static load,especially for deep roadways in a state of stress concentration,a large amount of strain energy is stored in the coal layer and the roof.When the coal body on both sides of the roadway is destroyed,the roof will rebound and release strain energy,which will produce a dynamic loading effect on the coal body.In order to study the dynamic rebound energy release process of the roof and its impact on the impact manifestation(coal body of the roadway)when the coal body on both sides of the roadway is destroyed,this paper uses theoretical analysis,laboratory tests,numerical simulation methods to establish the "roof-coal body" "Two-body combination model,analyze the roof dynamic rebound mechanism law and influencing factors,and establish a" roof-lane coal body-internal coal body "three-body combination model to analyze the failure of the internal coal body,the roof rebound on the coal body In the end,the influence of the rebound dynamic load of the roof on the instability and failure characteristics of the surrounding rock was studied.The main conclusions are as follows:(1)Through the theoretical analysis and numerical simulation method to study the rebound energy release process of roadway roof.When the coal body is destroyed,the energy released by the rebound of the roof is inversely proportional to the elastic modulus of the roof itself,and is proportional to the unloading of the contact surface before and after the rebound of the roof;the destruction of the coal will cause the rebound of the roof in a larger area above it.That is,when the internal coal body is destroyed,the rebound phenomenon of the roof can also affect the coal body of the roadway,and the rebound rate attenuation is small.(2)Use a flexible testing machine to perform a uniaxial compression test on the coal body,monitor the acceleration change of the testing machine head with an acceleration sensor,and use FLAC3D to verify the test results and analyze the "top-coal" two-body combination structure roof return Bullet mechanism and influencing factors.The results show that the roof unloading rebounds when the coal body is destroyed,and the roof rebounding exerts a dynamic loading effect on the specimen.When the unloading amount increases,the roof rebounding speed increases from 0.0146m/s to 0.0855m/s,so the rebound speed of the top plate is directly related to the unloading amount;the rebound of the top plate exacerbates the degree of damage of the test piece.The rebound effect is inversely proportional to the elastic modulus of the top plate and proportional to the strength of the test piece.(3)Through the laboratory test and FLAC3D software,the rebound process and energy release rule of the "roof-strong specimen-weak specimen" three-body composite structure roof were studied.The results show that the three-body structure has two rebounds of the roof,which are sequentially caused by the failure of the weak and strong specimens.The roof releases 61.8%and 65.1%of the strain energy,of which the peak value of the first rebound velocity is 0.16m/s,the second rebound speed is positively related to the strength of the strong test piece,which is 0.118m/s,0.089m/s,0.132m/s,0.216m/s,0.326m/s,0.55m/s in order When the strength of the piece is strong enough,the second rebound speed of the weak test piece roof exceeds the first time,that is,the rebound of the roof caused by the destruction of the internal coal body,which can produce a more dramatic dynamic loading effect on the coal body of the gang.(4)Use FLAC3D software to perform dynamic analysis,simplify the dynamic load equation according to the test results and apply it to the coal and roof contact surface on the side of the roadway,and study the influence of the roofs rebound dynamic load on the instability and failure law of the surrounding rock of the roadway.The results show that the dynamic load disturbance of the roadway has increased the deformation of the surrounding rock,and the increase effect is:horizontal deformation of the side(57.94%)>vertical deformation of the side(24.53%)>vertical deformation of the roof(19.06%);dynamic load When the amplitude is increased from 1m/s to 5m/s,the horizontal deformation peak of the roadway coal body increases by 153.04%,and the damage range increases by 33.33%;the dynamic load action position of the roadway side is away from the roadway side from 1.5m After moving 2m in the direction,the horizontal deformation of the roadway coal body decreased by 24.09%,and the damage range was reduced by 22.22%;therefore,the roof rebound dynamic load mainly increased the horizontal movement of the coal body.