淹没射流冲击煤体应力模型及破煤临界条件研究

Study on stress model and critical conditions for coal breaking by submerged jet

为探究煤矿水力化卸压增透瓦斯治理作业中淹没射流破煤的临界条件,首先,基于紊动射流、接触力学及动量定理等理论,建立淹没射流冲击煤体应力模型,并对其进行离散数值求解;然后,分析淹没射流冲击煤体表面应力的分布特征,进而根据最大正应力准则确定淹没射流破煤临界条件;最终,以贵州金佳矿为例,开展淹没射流破煤现场验证试验。研究表明:射流冲击区内煤体的最大主应力为轴向压应力,冲击区外煤体的最大主应力为径向拉应力;冲击区内和冲击区外煤体表面的最大主应力均呈中心对称分布,而且随径向距离的增大而降低;淹没射流破煤的临界压力和临界喷嘴直径均随煤体强度和冲击靶距的增加而增大,而且靶距越大,煤体强度对临界条件的影响越大;淹没射流能够高效破碎现场松软煤层,而硬煤需要通过非淹没射流或伴随射流条件完成破碎。

In order to explore the critical conditions of coal breaking by submerged jet in the hydraulic pressure relief and permeability enhancement operation of coal mines,the stress model of submerged jet impinging on coal body was established by using the theories of turbulent jet,contact mechanics and momentum theorem.The distribution of surface stress on coal body under the submerged jet impinging was studied through discrete numerical solutions for the established stress model.Then,the critical conditions of coal breaking by submerged jets were determined according to the maximum normal stress criterion.Finally,the correctness of the above theory was verified through on-site tests of submerged jet coal breaking at Jinjia mine in Guizhou.The results show that the maximum principal stress of coal is axial compressive stress in the impact zone,while it is radial tensile stress outside the impact zone.Whether inside or outside the impact zone,the maximum principal stress on the coal surface,central symmetry,decreases with the radial distance.The critical pressure and nozzle diameter of submerged jet coal breaking increase with the coal strength and impact target distance.The larger the target distance is,the greater the impact of coal strength on critical conditions.A submerged jet is only suitable for crushing soft coal seams,while a non-submerged jet or accompanying jet can be used for crushing hard coal.