Numerical and Field Investigations of Tremors Induced by Thick-Hard Strata Fracture

Abstract

Large energy mining-induced tremors are generally caused by the rupture of thick-hard overlying strata, and the roadway is prone to rockburst danger under its dynamic load. Through numerical simulations, the laws and influencing factors of stress, deformation, fracture and energy caused by mining-induced tremors (red bed breaking) were revealed, and the results were verified by field observations. The main conclusions were obtained: (1) the tensile stress and the compressive stress were concentrated in the middle of the thick-hard rock and both sides of the goaf, which were prone to tensile and shear failure type caused by mining-induced tremors, respectively; (2) after the goaf was formed, the compressive stress around the roadway was transformed into tensile stress. When a strong mining-induced tremor occurred, the tensile stress increased further. Meanwhile, when it was close to the tensile strength of the coal around the roadway, a rockburst occurred; (3) the energy of the mining-induced tremor released by shear failure was larger than that of the tensile failure. With the increase in shear strength of the roof, the released energy also increased; (4) according to the frequency-spectrum of the mining-induced tremors located in the extremely thick-hard overlying strata above the working face in the Baodian coal mine, the dynamic load generated by the tremors was superimposed on the high static load around the roadway, which was very likely to induce the instability of the roadway. The research conclusions have certain guiding significance for rockburst prevention in coal mines with thick-hard strata roofs.

Keywords

• thick-hard overlying strata
• rockburst
• mining-induced tremors
• microseismic monitoring
• dynamic load