急倾斜特厚煤层群开采岩柱破断回弹诱冲机理力学分析

Mechanical analysis of rock burst induced by fracture and rebound of rock pillar in mining of steeply inclined extra-thick coal seam group

  • 摘要: 为揭示急倾斜特厚煤层群开采煤层间岩柱的破断诱冲机理,以乌东煤矿急倾斜特厚煤层群开采为工程背景,在对现场实测结果综合厘定与分析的基础上,采用理论分析方法,通过构建岩柱破断前、后2个稳态时的力学模型,对比分析结构瞬变激励下急倾斜采场煤岩的力学响应特征和煤层间岩柱的破断诱冲机理。结果表明:在急倾斜特厚煤层群开采中,煤层间岩柱的瞬时破断,会造成采场煤岩结构的瞬变,导致采场空间不同区域煤岩的受载特征与力学响应发生瞬变。其中,岩柱破断部分的顺向回转,会导致B3-6煤层上覆采空区的几何尺寸瞬时增大,充填体密实程度减小,对采空区顶板的支撑效应减弱,导致顶板载荷传递路径发生改变,作用在B3-6煤层顶板侧的载荷瞬时增大;对B1-2煤层的影响与之相反,作用在B1-2煤层底板侧的载荷会瞬时减小。与此同时,煤层中岩柱的逆向回弹—振动,会对相邻的B1-2和B3-6煤层形成冲击作用,但由于煤层中岩柱的瞬态响应是向B3-6煤层方向回弹,且受煤岩破裂、阻尼等能量耗散影响,振动过程中始终不能运动到其初始位置;所以,煤层中岩柱的回弹—振动,会在B3-6煤层的底板侧形成瞬时加载,但在B1-2煤层的顶板侧是瞬时卸载。因此,岩柱破断后不同区域的回转和回弹运动,会使B3-6煤层处于瞬时加载状态,但对B1-2煤层是瞬时卸载;且较回转运动而言,后者的影响更为显著;这也是岩柱破断后B3-6煤层容易发生冲击地压,而B1-2煤层不容易发生冲击地压的内在原因。在实际工程中,可基于调结构、控响应的防治理念,通过将B1-2与B3-6煤层错水平布置开采等,可有效降低岩柱破断后的回弹与加载效应,实现对岩柱型冲击地压的源头治理。

     

    Abstract: In order to reveal the mechanism of breaking and inducing rock pillars between coal seams in steeply inclined and extra thick coal seam group mining, the mining of steeply inclined and extra-thick coal seam group in Wudong Coal Mine is taken as the engineering background. Based on the comprehensive determination and analysis of the field measurement results, the theoretical analysis method is used to construct the static model of the two steady states before and after the rock pillar is broken. The mechanical response characteristics of the coal and rock in the steeply inclined stope under the transient excitation of the structure and the breaking mechanism of the rock pillar between the coal seams are compared. The results show that in the mining of steeply inclined and extremely thick coal seam group, the instantaneous fracture of rock pillars between coal seams causes the transient change of coal and rock structure in the stope, resulting in the transient change of load characteristics and mechanical response of coal and rock in different areas of the stope space. Among them, the forward rotation of the broken part of the rock pillar leads to the instantaneous increase of the geometric size of the overlying goaf of the B3-6 coal seam, the decrease of the compactness of the filling body, and the weakening of the supporting effect on the roof of the goaf, resulting in the change of the load transfer path of the roof and the instantaneous increase of the load on the roof side of the B3-6 coal seam. On the contrary, the load acting on the floor side of B1-2 coal seam decreases instantaneously. At the same time, the reverse rebound-vibration of the rock pillar in the coal seam forms an impact on the adjacent B1-2 and B3-6 coal seams. However, due to the transient response of the rock pillar in the coal seam is rebounding in the direction of the B3-6 coal seam, and is affected by energy dissipation such as coal and rock fracture and damping, it cannot move to its initial position during the vibration process. Therefore, the rebound-vibration of the rock pillar in the coal seam forms instantaneous loading on the floor side of the B3-6 coal seam, but instantaneous unloading on the roof side of the B1-2 coal seam. Therefore, the rotation and rebound movement of different regions after the rock pillar is broken causes the B3-6 coal seam to be in the instantaneous loading state, but it is instantaneous unloading for the B1-2 coal seam. Therefore, the rotation and rebound motion of different regions after the rock pillar is broken makes the B3-6 coal seam in the instantaneous loading state, but the B1-2 coal seam is instantaneous unloading. And compared with the rotary motion, the influence of the latter is more significant. This is also the fundamental reason why B3-6 coal seam is prone to rock burst after rock pillar fracture, while B1-2 coal seam is not prone to rock burst. In practical engineering, based on the prevention and control concept of 'adjusting structure and controlling response', the rebound and loading effects after rock pillar breaking can be effectively reduced by mining B1-2 and B3-6 coal seams in a staggered horizontal arrangement, so as to realize the source control of rock pillar rock burst.

     

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