真三轴应力下水射流冲击不同层理面倾角煤的破坏机制  

Failure mechanism of a water jet impacting coal with different bedding plane angle under true triaxial stresses

作　　者：葛兆龙[1,2] 马世榃 周哲[1,2] 张旭[1,2] 常文旭 GE Zhaolong;MA Shitan;ZHOU Zhe;ZHANG Xu;CHANG Wenxu(School of Resources and Safety Engineering,Chongqing University,Chongqing 400044,China;State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学资源与安全学院,重庆400044 [2]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044

出　　处：《振动与冲击》2024年第22期10-19,共10页Journal of Vibration and Shock

基　　金：国家自然科学基金(52274112);重庆市技术创新与应用发展专项(CSTB2023NSCQ-JQX0028)。

摘　　要：煤的层理面倾角(bedding plane angle,BPA)对射流破岩的效果影响显著。为探讨真三轴应力下不同BPA煤的射流破坏机制,开展了不同BPA煤在真三轴应力下的纯水射流冲蚀试验。结果表明,当煤的BPA较低或较高时,射流冲击分别容易形成锥形破碎坑和裂缝坑,破碎坑开口随着BPA的增大由圆形逐步向椭圆形过渡,煤的破坏模式由剪切破坏主导转变为拉伸-水楔效应主导。随着BPA增至60°,破岩体积增加了154.35%。当施加三轴应力时,煤层理面对射流破煤性能的影响被抑制,不同BPA煤的破坏模式仅呈现圆孔破碎坑,水锤压力引起的剪切破坏是煤在三轴应力下破坏的主要原因,60°BPA煤样的破坏体积减少了95.60%,相比其他倾角降低幅度达到最大。BPA对煤的轴向损伤演化具有驱动作用,随着倾角增大,轴向损伤发生波动。当施加三轴应力时,三轴应力抑制了射流破煤的损伤演化,煤的轴向损伤出现收缩。煤的破碎坑壁面的扫描电子显微镜(scanning electron microscope,SEM)结果表明:当施加三轴应力时,0°BPA煤样的破碎孔壁不再出现微裂隙与脆性剪切破坏的痕迹,并且孔隙的数量与尺寸大幅减小;60°BPA煤样的破碎孔壁不再出现水楔作用导致的大量锯齿状痕迹,三轴应力下不同BPA煤的破碎孔壁面均出现明显的延性剪切破坏特征。The angle of coal's bedding planes significantly affects the performance of jetting in rock fracturing.To investigate the mechanism of failure and damage characteristics of coal with different bedding plane angle(BPA) under true triaxial stress conditions,erosion experiments using pure water jets were conducted at various BPA and triaxial stress levels.The experimental results indicate that the angle of coal's bedding planes has a pronounced impact on the fracturing capacity of the water jet.For coal samples with lower and higher BPA,the water jet impact tends to form cone-shaped erosion pits and crack-like pits,respectively.Additionally,the opening of the erosion pits transits from circular to elliptical as the BPA increases,and the failure mode shifts from shear-dominated to water-wedge effect-dominated.With the increase of coal's BPA,the fracturing performanceis improved by 154.35%,reaching its peak when the BPA is 60°.As the BPA of coal increases,the orifice of the broken pit transits from circular to elliptical.Under the application of triaxial stresses,the destruction of coal samples with various BPA only presents circular erosion pits mode,and the shear damage caused by water hammer pressure becomes the primary reason of the failure of coal samples under triaxial stresses.The difference among the jetting damage modes of samples with different BPA is significantly reduced,and the influence of coal's bedding planes on the fracturing capacity of the water jet is significantly weakened.The fracturing volume reduction of 60° BPA samples reaches 95.60%,which is the maximum reducing rate observed.The CT scan results reveal that the tension damage caused by the water wedge effect is the primary factor affecting the failure characteristics,and it reaches the most severe impact at 60° BPA.The area of jet damage decreases with the increase of triaxial stresses.The scanning electron microscope(SEM) results indicate that triaxial stresses cause the closure of pre-existing cracks and micro-damage in coal samples with

关 键 词：径向射流钻井技术 煤层理面 三轴应力 损伤破坏 

分 类 号：TH212[机械工程—机械制造及自动化] TH213.3