空气动力造穴技术原理及单井掏煤量计算方法

Principle of air-cavitation technology and calculation method of single well coal digging quantity

空气动力造穴技术在瓦斯消突领域取得了良好效果,但其技术原理尚不明确,为明确空气动力造穴技术原理,为下一步优化施工提供理论依据及数学计算方法,特进行以下研究。结合实际工程,对空气动力造穴技术流程及力学过程进行了理论分析,提出了空气动力造穴技术原理假说,并提出了基于该假说的2个推论,以期通过对推论的证明佐证假说的正确性;设计并进行了快速卸载围压三轴压缩实验,采用恒定轴压、卸载围压的卸压方法,控制围压液缸排液量恒定,观察煤体应力-应变过程,同时在煤样前端加载气压,通过观察流经煤体的气体流量变化判断煤样的破坏时机;在此基础上给出了弹-塑性过程数学模型及单井掏煤量计算方法;最后结合工程背景,使用Comsol软件引用数学模型对"松散带"范围进行了数值计算,并对空气动力造穴单井最大掏煤量进行了预测。快速卸载围压三轴压缩实验结果表明煤体的力学过程可被分为弹性阶段、弹塑性阶段及塑性阶段并给出了应力-应变曲线,进一步分析认为其力学过程可用非线性弹性胡克定律进行描述;计算所得的空气动力造穴单井最大掏煤量接近于实际工程单井出煤量;以上结果表明,空气动力造穴技术原理是:以向井内注入高压气体后快速卸压为手段,提升煤层洞穴壁面处孔隙压力,通过多次重复施工,剥离"松散带"煤体并通过气举手段带出地面,从而形成洞穴;明确了煤体在快速卸载围压条件下的应力-应变过程,并给出了弹-塑性过程数学模型及单井掏煤量的计算方法,计算所得单井掏煤量接近于实际工程单井掏煤量,并且空气动力造穴注气压力与单次掏煤量成正比,证明了空气动力造穴技术原理假说推论的正确性,从而佐证了空气动力造穴技术原理假说。

The air-cavitation technology has applied and achieved a good result in the field of gas outburst elimination,but its technical principle is not clear.In order to clarify the air-cavitation technology principle and provide a theoretical basis and mathematical calculation method for the next step optimization and implementation,the following were performed in this study.Combined with the actual engineering,the air-cavitation technology process and mechanical process were theoretically analyzed,and the hypothesis of air-cavitation technology principle was proposed,and two inferences based on the hypothesis were proposed in order to prove the hypothesis by supporting the inference.The triaxial compression experiment of quick unloading confining pressure was designed and carried out.Using unloading confining pressure with a constant discharge velocity and a constant axial pressure,the coal body stress-strain process was observed,and at the same time in the coal sample the front end was loaded with a constant pressure,and the timing of destruction of the coal sample was judged by observing the change of the gas flow through the coal body.Based on this,a mathematical model of the elastic-plastic process and a single well coal digging quantity calculation method were given.Finally,the Comsol software was used in combination with the engineering background and the software used the mathematical model to numerically calculate the range of the"loose zone"and predict the maximum amount of coal that can be excavated by air-cavitation in a single well.The results of the rapid unloading confining pressure triaxial compression experiments show that the mechanical process of coal can be divided into elastic stage,elastoplastic stage and plastic stage,and the stress-strain curve is given.Further analysis believes that the mechanical process can be described with nonlinear elastic Hooke’s law.The calculated maximum air-cavitation single-well coal output volume is close to the actual engineering.Above results show that the air-cavitation technology principle is to quickly release pressure after injecting high-pressure gas into the well as a means,raise the pore pressure at the wall surface of the coal cave,through repeated operation,strip the"loose zone"coal body and take it out of the ground by gas lift,thereby form a cave.The stress-strain process of the coal body under the condition of rapid unloading confining pressure is clarified and the mathematical model of the elasto-plastic process and the calculation method of the single-well coal extraction are given.The calculated single-well coal outputs is close to the actual engineering.The amount of coal is directly proportional with injection pressure,which proves the correctness of the inference of the air-cavitation technology hypothesis,thus supports the aerodynamic cavitation technology hypothesis.