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基于断裂力学和重整化群理论,采用综合研究方法,从宏细观角度对开采扰动底板损伤岩层动态失稳机理进行了研究。结果表明,煤层回采后,底板岩层存在高应力束组成的主应力拱,最大主应力大小决定裂纹的起裂与扩展,裂纹的生长路径受控于最大主应力的方向。采场高支承压力引起岩层原始裂纹起裂,宏观上表现为底板岩层的预先剪切随机破坏;近场区域最大主应力场部分偏转,引起底板岩层中垂直应力显著降低、浅部水平应力急剧增加和斜向采空区方向产生高剪应力,迫使裂隙在原有扩展长度基础上进一步生长;工作面继续推进,采空区内底板岩层水平方向上压缩和竖向膨胀引起岩层拉破坏,当底板岩层损伤发展到临近损伤值时,极小范围的扰动被强烈放大,底板岩层由随机破坏转为“雪崩”式宏观断裂。
Based on fracture mechanics and renormalization group theory, a comprehensive research method was used to study the dynamic instability mechanism of disturbed rock damaged floor in macroscopic and microscopic view. The results show that after the coal mining, the main stress arch of high stress beam exists in the floor rock strata. The maximum principal stress determines the initiation and propagation of cracks. The growth path of the crack is controlled by the direction of the maximum principal stress. The high bearing pressure of stope caused the initial crack initiation in the rock stratum, which was macroscopically pre-shearing stochastic failure of the bottom strata. The partial maximal principal stress field in the near-field region was partially deflected, which caused the vertical stress in the floor rock stratum to decrease significantly and the horizontal stress in the shallow stratum to increase sharply And goaf direction to produce high shear stress, forcing the fissure to grow further on the basis of the original extension length. The working face continues to advance. The compression and vertical expansion of the floor rock strata in the goaf causes the rock strata to pull down. When the floor rock strata When the damage is approaching the damage value, the disturbance of a very small area is strongly amplified, and the rock stratum of the floor changes from “random damage” to “avalanche” macro-fracture.