基于能量传导机制的覆岩裂断损伤主控因素及表征

Main controlling factors and characterization of overburden fracture damage based on energy conduction mechanism

  • 摘要: 采场上覆岩层的运移和裂断是影响工作面矿压显现的重要因素。从能量角度对覆岩损伤及破坏特征进行研究,能够更好地了解采动影响下覆岩运移与破坏的行为规律和潜在风险,为采场合理的开采参数设计提供有效的指导。以陕西神府矿区青龙寺煤矿为研究背景,通过能量耗散理论从二维平面及三维空间的角度对覆岩裂断损伤的峰后变形破坏特征进行研究。创新性地提出了煤层开挖赋予上覆岩层势能的总能量计算方法。在此基础上,采用数值模拟和理论分析相结合的方法,建立了基于能量传导机制的覆岩损伤程度表征体系。基于能量平衡和有限差分理论,推导了岩石耗散能有限差分方程式,采用FISH语言将其写入FLAC3D应变软化模型,补充了软件能量计算模块,弥补了常规采用塑性区定性表征工程岩体开挖导致的破坏程度及类型的不足。通过定义损伤度指标量化表征了指标参数尺度效应的能量耗散程度,并结合青龙寺煤矿工作面地质条件模拟分析了工作面长度和推进速度对覆岩损伤程度的影响。覆岩损伤度随工作面长度、工作面推进速度的增加分别呈“S”型增长和减小。最终确定工作面长度应小于303.26 m,推进速度应控制在10.13~18.00 m/d并匀速推进。若工作面参数超过上述范围,开采损伤将会引起上覆岩层中主要控制层的破坏,进而导致损伤比大幅度增加。最后,结合青龙寺煤矿5-20108工作面推进速度与其工作面来压步距的相关关系,发现工作面推进速度的增加使得来压步距增长,矿压显现强度增强,整体覆岩损伤程度降低,进而验证了基于能量传导模型表征体系的可行性。

     

    Abstract: The migration and fracture of overlying strata during coal seam mining is an important factor affecting the strata behaviors in working face. By studying the damage and failure characteristics of overlying strata from the perspective of energy, the behavior law and potential risk of overlying rock migration and failure under the influence of mining can be better understood, which provides effective guidance for reasonable mining parameter design of longwall face. Based on the research background of Qinglongsi coal mine in Shenfu mining area, Shaanxi province, this paper studies the post-peak deformation and failure characteristics of overlying rock fracture damage from the perspective of two-dimensional plane and three-dimensional space through the energy dissipation theory. An innovative method has been proposed for calculating the total energy of overlying rock layers with gravity potential energy imparted by coal seam excavation. On the basis, an overburden damage degree characterization system was built based on energy conduction mechanism through the integration of numerical simulation and theoretical analysis. The finite difference equation for rock dissipative energy is derived based on energy balance and finite difference theory. This equation is then incorporated into the FLAC3D strain softening model using FISH language. This effectively supplements the software energy calculation module. This approach addresses the limitations of conventional qualitative characterization of damage degree and type resulting from engineering rock excavation due to plastic zone effects. The energy dissipation degree of the scale effect of the index parameter was quantitatively characterized by defining the damage degree index. Based on the geological conditions of the Qinglongsi coal mine longwall face, a simulation analysis was conducted to investigate the influence of longwall face length and advance speed on the damage degree of overlying strata. The overburden damage degree increases and decreases in an "S" shape with the increase of longwall face length and advancing speed, respectively. Finally, it was established that the optimal longwall face length should not exceed 303.26 m, while the appropriate range for the uniform advance speed is between 10.13 m/d and 18.00 m/d. If the parameters of the longwall face exceed the above-mentioned range, the mining-induced damage could result in the failure of key controlling layers in the overlying strata, leading to a significant increase in the damage ratio. Finally, the feasibility of the characterization system based on the energy transmission model was verified through an analysis of the advance speed and the corresponding strata pressure of the 5-20108 longwall face. It was found that the increase in the advancing speed of the longwall face resulted in an increase in the step distance of the periodical Weighting, an increase in the strength of the mining pressure manifestation, and a decrease in the overall degree of overburden damage.

     

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