碎软煤层空气动力造穴力学响应特征与破坏过程模拟

    Mechanical response characteristics and destruction process simulation of aerodynamic cavitation in soft and brittle coal seams

    • 摘要: 空气动力造穴作为一种针对碎软煤层的局部消突手段,在淮南矿区进行了应用并取得了良好效果。但空气动力造穴机理尚不明确,注气压力、保压时间等关键参数也无从优化。基于空气动力造穴实际工况,首先开展了快速卸载围压三轴压缩试验,对煤体快速卸载过程所表现出的力学特征进行测试;之后进行了空气动力造穴数值模拟试验,选择注气压力、保压时间作为变量,对注气增压过程中孔隙压力变化规律及单次放喷(快速卸压)过程煤体破坏深度进行研究。结果表明:随着围压卸载速率的增加,煤体在试验中所表现出的抗压强度、抗拉强度、黏聚力等参数降低,内摩擦角增大,煤体在快速变化的应力环境下更容易被破坏;当注气增压、保压时间不足60 min时,孔隙压力与保压时间成正比;单次注气−放喷过程煤体破坏深度为65 mm左右,注气压力与煤体破坏深度成正比。空气动力造穴煤体破坏机理:向煤层洞穴内注入高压气体后快速放喷,在短时间内煤体孔隙压力大于煤层洞穴气压,使煤骨架所受有效拉应力大于煤体抗拉强度,从而剥离煤体。

       

      Abstract: As a local outburst control method for soft crushed coal seam, aerodynamic cavitation has been applied in Huainan Mining Area of China and achieved good results. However, the mechanism of aerodynamic cavitation is not clear, and the key parameters such as gas injection pressure and pressure holding time cannot be optimized. Based on the actual conditions of aerodynamic cavitation, the confining pressure triaxial compression test of rapid unloading was carried out to test the mechanical characteristics of coal mass during rapid unloading. Then, a numerical simulation test of aerodynamic cavitation was carried out, and the pore pressure and the time of holding pressure were selected as variables to study the variation rule of pore pressure and the damage depth of coal body in single gas injection and blowout (rapid pressure relief) during the process of gas injection and pressurization. The results show that with the increase of confining pressure unloading rate, the compressive strength, tensile strength, cohesion and other parameters of coal in the test decrease, the internal friction angle increases, and the coal is more easily destroyed under the rapidly changing stress environment. When the gas injection and pressure holding time is less than 60 min, the pore pressure is proportional to the pressure holding time. The damage depth of coal body in the process of single gas injection and blowout is about 65 mm, and the gas injection pressure is proportional to the damage depth of coal body. Aerodynamic cavitation coal body failure mechanism: after injecting high pressure gas into the coal seam cave, the coal pore pressure is greater than the coal seam cave pressure in a short time, so that the effective tensile stress of the coal skeleton is greater than the tensile strength of the coal body, so as to peel the coal body.

       

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