磨料气体射流冲蚀磨损岩石特征分析

When the abrasive gas jet is used for auxiliary drilling and pressure relief and permeability enhancement, it can avoid hole collapse and thus improve the recovery rate. Defining the rock-breaking characteristics of the abrasive gas jet is an important theoretical basis for promoting the application of the abrasive gas jet. However, the current abrasive gas jet erosion-wear models ignore the effect of reflected abrasives. For this reason, experiments on the erosion of limestone by abrasive gas jets under different abrasive types and different target distances were carried out. The erosion characteristics of different areas of the erosion pits were analyzed by using electron microscope scanning, and the movement trajectory of abrasives during the erosion of limestone was analyzed in combination with the discrete element model to define the erosion-wear characteristics of the abrasive gas jet and the effect of reflected abrasives. It was concluded that when the abrasive gas jet erodes limestone, the shape of the erosion pit is approximately an inverted cone, and there is an annular platform at the bottom of the erosion pit, and below the annular platform is the bottom of the erosion pit in a spherical shape. The main reason for this shape of the erosion pit is the particularity of the flow field structure of the abrasive gas jet. There are annular regions at the axis and boundary of the abrasive gas jet, and no abrasives exist in the annular regions. The incident abrasives at the axis are the main factor in forming the spherical shape. After reflection, the abrasives tend to move towards the annular region. During the reflection process, the diameter of the spherical shape and the erosion pit is enlarged, and an annular platform is formed. The bottom of the spherical shape is caused by the impact stress wave of the incident abrasives leading to rock failure, the side of the spherical shape is caused by multiple plastic deformations due to the reflected abrasives, there are plastic deformations caused by the incident abrasives and fatigue failures caused by the reflected abrasives at the annular platform, and the side of the erosion pit is mainly caused by fatigue failures due to the reflected abrasives. The hardness of the abrasives has no impact on the causes of erosion-wear and the characteristics of wear failure of the coal-rock mass. However, harder abrasives have a higher roughness when eroding the surface of the coal-rock and at the same time have a higher rock-breaking efficiency.

磨料气体射流在辅助钻孔和卸压增透时,能够避免塌孔,从而提高采出率。明确磨料气体射流破岩特征是推广磨料气体射流应用的重要理论基础。但目前的磨料气体射流冲蚀磨损模型忽略了反射磨料的作用。为此,开展了不同磨料种类和不同靶距条件下,磨料气体射流冲蚀灰岩实验,采用电镜扫描冲蚀坑不同区域的冲蚀特征进行分析,结合离散元模型分析磨料在冲蚀灰岩过程中的运动轨迹,明确磨料气体射流冲蚀磨损特征以及反射磨料的作用。得出磨料气体射流冲蚀灰岩时,冲蚀坑的形态大致为倒圆锥形,在冲蚀坑底部存在环形平台,环形平台下面为类球体状的冲蚀坑底部。造成这种冲蚀坑形态的主要原因为磨料气体射流流场结构的特殊性,在磨料气体射流轴心和边界处存在环形区域,环形区域内没有磨料存在。轴心处入射磨料是形成类球体的主要因素,磨料反射后趋向环形区域运动,在反射过程中,扩大了类球体和冲蚀坑直径,并形成了环形平台。类球体底部是以入射磨料的冲击应力波导致岩石破坏,类球体侧面是反射磨料造成的多次塑性变形,环形平台处存在入射磨料导致的塑性变形和反射磨料导致的疲劳破坏,冲蚀坑侧面主要以反射磨料产生疲劳破坏为主。磨料硬度对煤岩体冲蚀磨损诱因和磨损破坏特征没有影响。但较硬磨料冲蚀煤岩表面具有更高的粗糙度,同时具有更高的破岩效率。