高级检索

基于含水率效应的冲击煤体三轴加卸载钻进试验力学行为及其响应机制

Experimental study on mechanical behavior and response mechanism of triaxial loading-unloading drilling in impact coal under the effect of water content

  • 摘要: 煤层冲击倾向性强、顶板富水等是导致蒙陕矿区钻屑法监测失效的主要原因,以陕西彬长矿区某富水冲击地压矿井2号煤层为研究对象,设计了三轴加卸载钻进试验(含水率为0、2.7%、5.4%和7.8%;应力水平为36~46、48~58和60~70 MPa),探究了不同含水条件和不同应力状态下冲击煤体钻进力学行为,从煤体弱化以及煤粉黏结研究视角,初步揭示了水及应力对钻屑法评价冲击危险的影响机制。研究结果表明:① 水作用下煤体各物理力学参数均发生不同程度的劣化现象,其中塑性软化系数对理论钻屑量的影响程度最大;② 当煤体含水率w≤2.7%时,水对钻屑量的影响甚微,应力水平提升使试验钻屑量趋近理论值;当煤体含水率w≥5.4%时,水对钻屑量的黏结作用增强,在高应力、高含水率条件下,试验钻屑量显著降低;③ 由于煤体内部颗粒与水发生物理、化学作用,导致钻孔周边塑性区半径增加,煤体变形能力增强;而随着应力水平提升,钻孔周边应力增大,煤体内部能量积聚,变形加剧,2者共同作用下增加了钻杆切割的钻屑量;④ 在含水率小于25%范围内,随着含水率的增加,煤粉颗粒间液桥力增大,促使其在钻孔中团聚黏附,从而导致钻屑量减少。研究结果可为蒙陕地区富水冲击地压矿井钻屑法评价冲击危险提供重要理论依据。

     

    Abstract: Stronger burst tendency of coal seams and rich water in the roof are the key factors leading to the failure of drilling cuttings method in the Inner Mongolia Shaanxi mining area. This article takes the No.2 coal seam of waer-rich rock burst coal mine in the Binchang mining area as the research object, a triaxial loading-unloading drilling test was designed (moisture content of 0、2.7%、5.4% and 7.8%; stress levels of 36-46、48-58 and 60-70 MPa), to explore the mechanical behavior of coal drilling under different water content and stress states. From the perspective of coal weakening and coal powder bonding, preliminarily reveal the influence mechanism of water and stress on the rock burst risk evaluation by the drilling cuttings method. The results show that: ① Under the influence of water, the physical and mechanical parameters of coal mass undergo varying degrees of degradation, and the plastic softening coefficient has the greatest impact on the theoretical drilling amount; ② When the moisture content of coal mass is w≤2.7%, the influence of water on the amount of drill cuttings is minimal, and an increase in stress level brings the experimental drill cuttings amount closer to the theoretical value; When the moisture content of coal mass is w≥5.4%, the bonding effect of water on the amount of drilling cuttings is enhanced, under the conditions of high stress and high water content, the drilling cuttings decreased significantly; ③ Due to the physical and chemical interaction between coal particles and water, the radius of plastic zone around the borehole increases, and the deformation capacity of coal mass is enhanced. As the stress levels rise, the stress around the drilling hole increases, the energy inside the coal body accumulates, and the deformation intensifies, the combined action of the two increases the amount of cuttings in drill pipe cutting; ④ In the range of water content less than 25%, as the water content increases, the increase of the liquid bridge force between the pulverized coal particles promotes the agglomeration and adhesion in the drilling hole, which leads to the reduction of drilling cuttings. The research results can provide an important theoretical basis for the evaluation of rock burst risk by drilling cuttings method in the rich water rock burst coal mine in Inner Mongolia and the Shaanxi mining area.

     

/

返回文章
返回