巨厚煤层下分层开采邻近采空区破断岩体分形继发性演化机理

Fractal secondary evolution mechanism of fractured rock mass in adjacent goaf areas under extremely thick coal seam lower slice mining

为掌握新疆巨厚煤层开采扰动邻近采空区破断岩体分形继发性演化机理,以新疆某高瓦斯矿井巨厚煤层工作面为试验原型,利用大型二维物理相似模拟试验平台,开展巨厚煤层开采扰动邻近采空区破断岩体分形继发性演化机理试验,并结合分形理论定量表征邻近采空区破断岩体裂隙分布特征.试验结果表明:二次扰动邻近采空区破断岩体分形维数演化规律,随着下分层工作面推进,上覆采空区原有稳定结构被再次激活,岩体中铰接结构向下部破断岩体传递,使得邻近采空区岩层破断裂隙更为复杂,而后原激活区域逐渐稳定,形成新的趋于稳定的岩体结构,邻近采空区破断岩体产生继发性演化;得到邻近采空区破断岩体分形维数继发性演化机理,基于工作面推进过程中不同时期、不同区域邻近采空区破断岩体分形维数的继发性演化特征,随工作面推进,邻近采空区破断岩体周期性循环“激活—构建—稳定”;将邻近采空区破断岩体划分为3区,即:分形维数继发性演化激活区、分形维数继发性演化构建区、分形维数继发性演化稳定区,研究结果将进一步为巨厚煤层瓦斯抽采钻孔布置参数的优化提供一定的理论指导.

To master the mechanism of fractal secondary evolution of fractured rock mass in ad-jacent goaf areas disturbed by mining in Xinjiang's extremely thick coal seams,an experiment was conducted using a large-scale two-dimensional physical similarity simulation platform,taking a high-gas mine in Xinjiang with a extremely thick coal seam working face as the experi-mental prototype.The experiment aimed to explore the fractal secondary evolution mechanism of the fractured rock mass in adjacent goaf areas under mining disturbance.Combined with fractal theory,the fracture distribution characteristics of the fractured rock mass in the adjacent goaf areas were quantitatively characterized.The experimental results show that as the sublevel working face progresses,the original stable structure of the overlying goaf is reactiva-ted.The hinge structures within the rock mass are transmitted to the lower part of the frac-tured rock mass,complicating the fracture cracks in the adjacent goaf areas.Subsequently,the initially activated area gradually stabilizes,forming a new,more stable rock mass structure.This leads to the secondary evolution of the fractured rock mass in the adjacent goaf areas;Un-derstanding the fractal dimension secondary evolution mechanism of fractured rock masses in adjacent goaf areas,based on the characteristics of secondary evolution of the fractured rock mass fractal dimensions during different periods and regions as the working face progresses,shows that the fractured rock masses in adjacent goaf areas undergo a cyclical pattern of"acti-vation-construction-stabilization"with the advancement of the working face.The fractured rock mass in adjacent goaf areas is divided laterally into three zones:the activation zone of sec-ondary evolution of fractal dimension,the construction zone of secondary evolution of fractal dimension,and the stabilization zone of secondary evolution of fractal dimension.These find-ings provide theoretical guidance for optimizing the layout parameters of gas drainage boreholes in extremely thick coal seams.