To elucidate the influence of gas channel permeability resistance around dual-prevention boreholes in coal mines with compound disasters of coal and gas outbursts and rock bursts, triaxial permeability tests were conducted on single-graded and composite specimens with varying heights. Analyzing the relationship between permeability and specimen height, revealed the size effect of permeability. The head loss along the flow path model was introduced to characterize permeability considering the frictional head loss along the flow path (CFR). The zonal permeability characteristics within the influence area of dual-prevention boreholes were clarified. The results indicate that the primary mechanism behind the permeability size effect is the intensification of inertial effects with increasing seepage channel length. Permeability characterized by the CFR, which accounts for this inertial effect, can be used to identify dominant gas migration pathways. The study confirms that coal mass size is a key factor influencing affecting permeability capacity, providing a theoretical basis for optimizing borehole layout and enhancing gas extraction efficiency.
原煤取自某煤矿11240工作面,煤层具有高瓦斯压力与冲击地压倾向性,易自燃。顶板为薄层状泥岩,变形量较大,易发生冒顶、偏帮事故。原煤经过破碎、筛选、级配、塑形等阶段制成所需煤样。利用电动磨粉机将原煤破碎成颗粒状,再用200型标准检验筛分机将颗粒分选成0~1.25 mm的6种粒径区间。根据泰波(TALBOL A N)级配设计方法,计算所需级配试样的Talbol幂指数[22]。
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