Numerical Simulation of Collapse Disaster Before and After Weakening of Thick and Hard Roof

Nao LV; Haibo WANG

doi:10.11872/j.issn.1005-2518.2019.02.257

Highlights

In view of the impact disaster caused by large area roof caving on mechanical equipment and workers in mining area，the related research was conducted relying on 210108 working face of Xinji No.2 Mine.According to the difference of block volume before and after roof weakening.A a three-dimensional calculation model of two kinds of caving bodies with the same height and width，coal seam，goaf and floor is established by using ANSYS/LS-DYNA finite element software.The calculation adopts Euler-Lagrange fluid-solid coupling algorithm.Rock and coal are described by Lagrange mesh and Lagrange element，air is described by ALE mesh and Euler element.The cloud map of hurricane velocity in goaf and roadway ，and the cloud map of effective stress in the bottom of coal seam in typical moment behind roof collapse are obtained by simulation under two kinds of calculation conditions.The variation rule of hurricane wind speed in roadway caused by collapse of different volume before and after roof weakening and the influence of impact load on coal seam in working face are analyzed.The results show that: For two kinds of condition，the attenuation law of hurricane velocity in goaf and roadway is basically the same，but the distribution characteristics of effective stress at the bottom of coal seam are different.From goaf to roadway entrance，hurricane speed tends to increase，and the wind speed increases sharply at roadway entrance，but the wind speed decreases with the increase of the distance between the location and the roadway entrance.With the increase of roof falling time，the wind speed in the roadway rises as a whole，but the attenuation and deceleration decay rate of the wind speed in the roadway decreases gradually，and the peak wind speed decreases logarithmically with the increase of the distance between the location and the roadway entrance.After roof weakening，the length of collapse body decreases，and hurricane wind speed decreases at different times.The maximum wind speed value ofin roadway entrance decreases from 298.62 m/s to 224.89 m/s，which decreases by 25 $%$ ，and the reduction increases gradually with the increase of the distance to roadway entrance，which is 42 $%$ at 90 m.According to the fitting formula of the relationship between peak wind speed and distance，when the maximum allowable wind speed is 6 m/s，the influence range of Hhurricane after roof weakening decreases from 247 m to 158 m，which reduces by 36 $%$ .Large area of roof collapse causes stress concentration in coal seam of working face.After roof weakening，the stress distribution in coal seam of working face is more uniform，and the peak value of maximum effective stress decreases from 10 MPa before weakening to 4.3 MPa，which decreases by 57 $%$ .Controlling the cyclic step distance of roof weakening caving below 30 m can significantly reduce the impact range of hurricane and the impact load on the stability of coal seam in working face.

Cite this article

Nao LV , Haibo WANG . Numerical Simulation of Collapse Disaster Before and After Weakening of Thick and Hard Roof[J]. Gold Science and Technology, 2019 , 27(2) : 257 -264 . DOI: 10.11872/j.issn.1005-2518.2019.02.257

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