超高压水射流作用下岩石损伤破碎机理

Rock Damage Mechanisms under Ultra-high Pressure Water Jet Impact

由于水射流的高紊动与岩石材料的复杂性,水射流作用下岩石破坏机理的研究一直都是难点问题。运用全解耦流固耦合理论,建立超高压水射流冲击岩石介质的数值分析模型,射流采用标准k-ε模型和控制体积法,岩石采用线弹性和有限元法,计算分析淹没条件下岩石介质在水射流冲击作用下内部的应力分布规律。其次,根据岩石介质内部应力分布特征,基于岩石微元强度遵循Weibull分布的概率理论,将Mohr-Coulomb破坏准则作为随机分布变量,建立岩石损伤变量演化方程和连续损伤统计本构模型及用量纲一破坏系数来表征岩石破坏的准则。再次,按建立的流固耦合分析模型、岩石损伤模型和破坏准则,运用分阶段法对水射流的破岩过程进行了数值分析。最后,运用扫描电镜对水射流切割岩石断口形貌进行观测试验,分析岩石在超高压射流作用下微观破坏机制,主要有穿晶断裂和剪切错动两种形式,进一步验证数值模拟分析的结果,建立起水射流破岩过程中岩石微观破坏机制和宏观断裂分析的桥梁。

Research on the damage mechanism of rock under the action of water jet has always been a difficult problem due to high turbulence of water jet and complicacy of rock material. According to fully-decoupled fluid-structure interaction （FSI） theory, the standard k-e two equations and control volume method for water jet, and the elastic orthotropic continuum and finite element method for rocks, are employed respectively to establish a numerical analyzing model of ultra-high pressure water jet impinging on rock. In terms of the stress distribution of rock interior, which is computed under submerged water jet with different velocities, and based on the theory that the rock micro-unit strength obeys Weibull probability distribution, a theoretical equation of damage variables evolution and a rock statistical constitutive model are developed, with Mohr-Coulomb damage criterion as distribution variable. A damage criterion, with non-dimensional coefficient to characterize rock damage, is also set up for analyzing rock failure mechanism with water jet. The process of jet impact on the rock is simulated, by using the FSI model, the statistical constitutive damage model and the damage criterion. Micro failure mechanism test and analysis with scanning electron microscope （SEM） for rock failure surface by jets cutting were performed, whose results show that the micro-mechanism of rock failure due to water jet impingement is a brittle fracture in the condition of tensile and shearing stress. The test results also agree well with the numerical simulation analysis, which constructs a bridge between the micro-failure mechanism and macro-breaking analysis of rock with water jets impact. The investigation affords a method for studying the mechanism of rock failure under ultra-high pressure water jet impingement.