基于赵固二矿煤岩损伤程度范围确定及渗透率演化规律研究

Determination of the damage degree of coal rocks and study on the evolution law of permeability based on Zhaogu No.2 Coal Mine

我国东部矿区深埋薄基岩厚煤层的开采面临着许多技术难题。受工作面开挖卸荷效应的影响,覆岩将发生大变形非连续破坏,而上覆岩层的非线性破坏是导致厚冲积层中水沙涌入工作面的根本原因。为了确定煤层及覆岩的损伤程度范围以及渗透率的演化规律,采用现场实测与数值模拟手段,以超声波波速的分布规律定量表征煤壁的损伤程度范围,以覆岩塑性区的高度和体积表征覆岩的损伤程度范围,并对FLAC3D的渗流模式进行二次开发,分析工作面推进过程中覆岩及采空区渗透率的演化规律。研究结果表明:煤壁的损伤范围与超前支承压力峰值范围一致,6~7 m;覆岩塑性区的高度以及损伤程度随着工作面推进距离的增大而增大,当工作面推进至130 m时,覆岩达到充分采动,塑性区形状呈“马鞍”形分布;隔水层未破坏前岩体的渗透率与垂直应力呈负指数分布,隔水层破坏后高渗透率区域呈明显的分区现象,采空区岩体的渗透率随着冒落矸石的逐渐压实而降低。通过覆岩高渗透率范围的分布确定水沙渗流的主要区域,为赵固二矿14030工作面顶板突水溃沙的防治提供理论依据。

There are many technical problems with the mining of deep thick coal seams with thin bedrock in the mining areas in eastern China.Due to the influence of the excavation unloading effect of the working face,which is bound to cause large deformation and discontinuous failure of the overburden,the nonlinear failure of the overburden is the fundamental reason for the influx of water and sand into the working face in the thick alluvium.In order to determine the damage degree range of coal seam and overburden and the evolution law of permeability,this paper adopts the means of field measurement and numerical simulation to quantitatively characterize the damage zone of the coal wall from the distribution law of ultrasonic wave velocity and that of the overburden from the height and volume of overburden plastic zone.A seepage mode of FLAC3Dwas developed,which analyzed the evolution law of permeability of overburden and goaf during retreating the longwall panel.The results show that the damage zone of the coal wall is consistent with aera of the peak front abutment pressure,about 6~7 m.The height and damage degree of the plastic zone of the overburden increase with advancing distance of the working face.When the working face advances to 130 m,the overburden reaches full mining,and the plastic zone is distributed in a saddle shape.The permeability and vertical stress of the rock mass before the failure of the impermeable layer show a negative exponential distribution.After the failure of the impermeable layer,the high permeability area shows an obvious zoning phenomenon.The permeability of the rock mass in the goaf decreases with the gradual compaction of the caved roof.The main area of water and sand seepage is determined by the distribution of a high permeability range of overburden,which provides a theoretical basis for the prevention and control of water inrush and sand burst in the roof of 14030 working face of Zhaogu No.2 Coal Mine.