基于数值模拟的厚煤层回采期间覆岩采动应力及能量变化研究

Stress and energy changes of overburden rock during thick coal seam mining based on numerical simulation

为揭示厚煤层回采过程中的覆岩采动应力及能量演化规律,采用FLAC^(3D)进行模拟,分析厚煤层回采期间覆岩“应力场-能量场-裂隙场”演化特征。结果表明,回采期间工作面前方出现超前支承压力,应力最大值距离煤壁5 m,应力集中系数从1.28增至1.79,工作面前方应力集中区超前影响范围约为45 m。煤层回采完毕,顶板发生垮落,采空区中部形成新的支撑点,最大集中应力为31.2 MPa,弹性能最大值降低至98.73 kJ,此时,采空区中部压实区积聚部分弹性能,为26.17 kJ。开切眼处两巷覆岩弹性能逐渐增加后保持稳定,最大值为21.57 kJ,巷道中部覆岩弹性能持续降低,而停采线处弹性能先小幅度增加后降低。顶板出现大面积拉伸破坏,从下到上依次分为拉伸破坏区、剪切破坏区和未破坏区。

In order to reveal the dynamic stress and energy evolution law of overburden during the mining process of thick coal seams,FLAC^(3D) was used to simulate and analyze the evolution characteristics of“stress field-energy field-fracture field”of overburden during thick coal seam mining.The results show that during the mining period,the advance support pressure appears in front of the working front,the maximum stress is at 5 m away from the coal wall,the stress concentration coefficient increases from 1.28 to 1.79,and the influential range of the advanced stress concentration area in the front of the working face is about 45 m.After the coal seam is mined out,the roof collapses,a new support point is formed in the middle of the goaf,the maximum concentrated stress is 31.2 MPa,and the maximum elastic energy is reduced to 98.73 kJ,and at this time,the elastic energy accumulated in the compaction zone in the middle of the goaf is 26.17 kJ.The elastic energy of the overburden rock in the two roadways at the cutting eye gradually increased and then remained stable,with a maximum value of 21.57 kJ,and the elastic energy of the overburden in the middle of the roadway continued to decrease,while the elastic energy at the stop line first increased slightly and then decreased.The roof has a large area of tensile failure,which is divided into tensile failure area,shear failure area and undamaged area from bottom to top.