摘要:
为揭示煤矿开采断层破碎带突水灾害发生机理,有必要深入研究断层破碎带岩体的孔隙结构和渗透特性。研制了破碎岩体渗流-应力耦合试验装置,提出了应力作用下级配破碎岩体孔隙结构测试和渗流试验方法,研究了应力和级配对破碎岩体孔径分布特征、孔隙分形特征和非线性渗流行为的影响规律,构建了基于核磁共振的承压破碎岩体渗透率预测模型。试验结果表明:(1)颗粒分形维数为2.6的连续级配和间断级配破碎岩体的孔径分布均为三峰结构,级配破碎岩体中小颗粒的缺失会导致孔隙率和最大孔径增大,降低破碎岩体的压缩性,增大应力可促使渗流孔向束缚孔转变,降低破碎岩体的压缩性。(2)渗流孔隙率对级配破碎岩体渗透率起主导作用,束缚孔隙率对渗透率的影响较小,增大应力会降低破碎岩体渗透性,大颗粒的缺失会导致级配破碎岩体渗透率减小。(3)连续级配和间断级配破碎岩体的非线性渗流特性均可用Forchheimer方程描述,应力影响下破碎岩体的渗透率和非Darcy流β因子变化趋势相反,小颗粒的缺失会导致级配破碎岩体非Darcy流β因子减小。(4)构建了基于核磁共振的级配破碎岩体渗透率预测模型,通过剔除束缚孔的影响并引入渗流孔的加权贡献,可显著提高级配破碎岩体渗透率预测效果的准确性。研究结果为发展煤矿采动突水灾害理论和防控技术提供了科学依据。
Abstract:
In order to reveal the mechanism of the occurrence of water inrush hazards in fault fracture zones in coal mining, it is necessary to study the pore structure characteristics and permeability of rock mass in fault fracture zones. A test device for fractured rock mass under coupled seepage and stress was developed. A method was proposed for determining the pore structure and hydraulic properties of fault rock mass under compression stress. The pore size distribution and nonlinear seepage behavior of fault rock mass affected by particle size distribution and stress were investigated. A permeability prediction model based on the nuclear magnetic resonance(NMR) was proposed. The experimental results show that(1) the pore size distribution of both continuously graded and gap graded rock mass with a particle fractal dimension of 2.6 shows a three-peak structure, and the absence of small particles in graded rock mass leads to the increase of porosity and maximum pore size, which decreases the compressibility of the fault rock mass sample.(2) The permeability of graded fractured rocks is dominated by the permeable porosity, and the bound porosity is less influenced by the stress. The increased stress and the absence of large particles lead to the decrease of permeability of fault rock mass sample.(3) The nonlinear seepage behaviors of both continuously graded and gap graded fault rock mass can be described by the Forchheimer equation, and the permeability and the β-factor of non-Darcy flow of fault rock mass vary in opposite trends under the influence of stress. The absence of small particles leads to a reduction in the β factor of graded fractured rock mass.(4) A NMR-based permeability prediction model for graded fault rock mass was proposed, which can significantly improve the accuracy of permeability prediction for graded fractured rock mass by removing the influence of bound pores and considering the weighted contribution of seepage pores. The results provide a scientific basis for revealing the mechanism of water inrush disaster and the prediction and prevention of water inrush disaster in coal mining.
百度学术
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