Study on the effect of coal seam thickness on rock burst

Aiming at the influence of coal seam thickness on rock burst, the effect of coal seam thickness on rock burst is proposed. The relationship between coal seam strain energy and its thickness is revealed by combining theoretical analysis, numerical simulation and engineering cases, and the formation mechanism of the effect of coal seam thickness on rock burst is studied. The effect of coal seam thickness on rock burst is verified by numerical simulation of the stability of surrounding rock around the coal roadway and engineering cases. The results show that under the same vertical stress, the greater the thickness of the coal seam in the coal-rock combination, the more the accumulated strain energy, and the greater the possibility of rock burst. With the increase of the rock-coal height ratio of the composite specimen, the uniaxial compressive strength increases gradually, the strain localization of the coal seam becomes more significant and the strain energy density increases continuously, while the expansion rate of the coal-rock composite specimen decreases, and the failure mode gradually changes from shear failure to tensile-shear composite failure and tensile failure. The influence of coal-rock height ratio on the strength of composite specimens is essentially the size effect of rock strength. For the composite specimens with small rock-coal height ratio, the tangential stress in the middle of the coal seam is small, and the lateral restraint of the rock layer is weak, then the uniaxial compressive strength of the composite specimens is close to that of the coal seam. For the composite specimens with large rock-coal height ratio, the lateral constraints of the upper and lower interfaces of the coal seam are superimposed in the middle of the coal seam, so that the whole is in an approximate three-dimensional stress state, and the bearing capacity of the composite specimens is significantly improved. With the increase of coal seam thickness, the failure area of roadway surrounding rock extends from the side to the roof and floor, and the failure depth of roadway side and roof and floor is increasing, and the possibility of impact instability is also increasing. The research results have significant implications for rock burst prediction and prevention.