高压水射流冲击下煤体初始失效形式分析

Analysis of initial failure mode of coal under high pressure water jet impact

高压水射流冲击下煤体初始失效机理研究有助于评价煤体损伤特征。以九龙矿2#煤层为研究对象,采用光滑粒子流体动力学(smoothed particle hydrodynamics, SPH)方法建立了水射流冲蚀煤体数值模型,结合von Mises理论分析了煤体在高压水射流冲击下内部应力分布及裂纹扩展特征,并基于Python编程图像处理技术量化表征了煤体内裂纹形成规律。研究结果表明:在射流冲击下煤体损伤演化过程分为3个典型区,即破碎区、初始裂纹形成区和裂纹扩展区。当射流接触煤体表面时,在水锤效应影响下煤体主要受剪应力作用形成破碎区;在初始裂纹形成区,煤体受到压剪应力及微小拉应力共同作用,初始裂纹萌生;随着水锤效应的消失,射流冲击引发的应力波导致煤体内部主要承受拉应力作用,形成裂纹扩展区。因此,在实际工程中可以通过实时监测射流冲击下煤体内部应力特征来判断其损伤程度。

The study on the initial failure mechanism of coal under the impact of high pressure water jet is helpful to evaluate the damage characteristics of coal. Taking 2#coal seam in Jiulong mine as the research object, the smoothed particle hydrodynamics(SPH) method was used to establish a numerical model of water jet erosion of coal, and von Mises theory was used to analyze the internal stress distribution and crack propagation characteristics of coal under high pressure water jet impact. Based on Python programming image processing technology, the crack formation law in coal was quantitatively characterized. The results show that the damage evolution process of coal mass under jet impact can be divided into crushing area, initial crack formation area and crack propagation area. When the jet contacts the coal surface, the crushing area is mainly formed by the shear stress under the influence of water hammer effect. In the initial crack formation area, the initial crack initiates under the combined action of compressive shear stress and micro tensile stress on the coal body. With the disappearance of water hammer effect, the stress wave caused by jet impact leads to the main tensile stress in the coal body, forming the crack propagation area. Therefore, in practical engineering, the damage degree can be judged by real-time monitoring the internal stress characteristics of coal under jet impact.