This paper aims to investigate the damage and fracture characteristics of rocks with different structures under water jet impact. Three types rocks including heterogeneous coal, homogeneous sandstone, and transversely isotropic shale, were selected as the impact target rock. Water-jet impingement experiments with jet velocities varying from 447 m/s to 774 m/s were conducted. The rock macro-breakage characteristics were obtained by describing the breakage patterns, measuring the erosion depth and area, and counting the cracks number. A 3D reconstruction method based on the computed tomography and digital image processing technology was proposed to visualize the internal breakage characteristics and quantitatively analyze the damage field distribution. Combined with fracture morphology from scanning electron microscope, the failure mechanisms of rocks with three structures under water jet impact were revealed. The results indicate that coal, sandstone and shale will experience different breakage patterns with the increasing jet velocity: layered transverse cracks → “十”-type crack network → splitting crack, only one spindle-shape erosion pit, surface debris spalling → layered transverse cracks → “T”-type crack network. The effects of jet velocity and rock structure on the evaluation indexes (such as erosion depth and damage area, the number and angle of transverse cracks) were investigated thoroughly. In addition, the relationships between total damage degree based on breakage volume and jet velocity, and between damage variable based on breakage area and erosion depth, were compared and discussed. The failure mechanisms of three rocks impacted by water jets are as follows: (i) the reflection and interference of stress wave combined with the pressured water wedge effect cause the layered breakage and longitudinal splitting breakage of heterogeneous coal; (ii) the grinding effect of back flow mainly accounts for the formation of spindle-shape erosion pit in homogeneous sandstone; (iii) the shock stress wave effect and bedding structure lead to the spalling of large shale block and layered breakage, and the reflected wave tensile accompanied with pressured water wedge effect cause the tensile splitting breakage.

本文旨在研究不同结构岩石在水射流冲击下的损伤和断裂特征。选择非均质煤、均质砂岩和横向各向同性页岩三类岩石作为冲击目标岩石。进行了射流速度从 447 m/s 到 774 m/s 变化的水射流冲击实验。岩石宏观破碎特征是通过描述破碎模式、测量侵蚀深度和面积以及计算裂缝数量来获得的。提出了一种基于计算机断层扫描和数字图像处理技术的3D重建方法，以可视化内部破损特征并定量分析损伤场分布。结合扫描电镜断口形貌，揭示了三种结构岩石在水射流冲击下的破坏机制。结果表明，随着射流速度的增加，煤、砂岩和页岩将经历不同的破裂模式：层状横向裂缝→“十”型裂缝网络→分裂裂缝，只有一个纺锤形侵蚀坑，地表碎屑剥落→层状横向裂缝→“T”型裂纹网。深入研究了射流速度和岩石结构对冲蚀深度和损伤面积、横向裂缝数量和角度等评价指标的影响。此外，比较和讨论了基于破碎体积和射流速度的总损伤程度与基于破碎面积和侵蚀深度的损伤变量之间的关系。三种岩石受水射流冲击的破坏机制如下： (i) 应力波的反射和干涉结合压力水楔效应导致非均质煤层状破碎和纵向劈裂破碎；(ii) 回流的研磨作用主要是在均质砂岩中形成纺锤形冲蚀坑的原因；(iii) 冲击应力波效应和层理结构导致大页岩块体剥落和层状破裂，反射波张拉伴随压力水楔效应导致张裂破裂。(ii) 回流的研磨作用主要是在均质砂岩中形成纺锤形冲蚀坑的原因；(iii) 冲击应力波效应和层理结构导致大页岩块体剥落和层状破裂，反射波张拉伴随压力水楔效应导致张裂破裂。(ii) 回流的研磨作用主要是在均质砂岩中形成纺锤形冲蚀坑的原因；(iii) 冲击应力波效应和层理结构导致大页岩块体剥落和层状破裂，反射波张拉伴随压力水楔效应导致张裂破裂。