应变率对岩石裂隙扩展规律的影响

为分析一种奥陶系沉积岩在单轴压缩条件下岩石的裂隙扩展规律,利用应力加载系统和VIC-3D观测系统等试验系统,并采用数字图像相关方法研究了单轴压缩下岩石表面裂隙扩展过程中应变场的变化特征。试验结果表明:在加载过程中,通过VIC-3D观测系统可得到整个加载过程中的全场应变演化规律,其中岩石表面数字散斑云图的高应变区不断增加,相应地岩石在弹塑性阶段就开始出现了轴向的微裂纹,当达到应力峰值为18.02 MPa时,主裂纹和周围出现的次生裂纹不断扩展延伸导致了试样的完全破坏;考虑到应变率对岩石力学特性的影响,结合单轴压缩下岩石试样表面裂隙周围应变场的变化特征,分析出了主裂纹Ⅰ和次生裂纹Ⅱ,Ⅲ,Ⅳ周围的应变率和裂纹扩展速率的关系,发现裂隙扩展速率和轴向应变率呈现较强的指数函数关系。研究结果揭示了这种沉积岩的裂隙扩展与延伸规律,可为防治煤矿动力灾害的发生提供参考。

Influence of strain rate on the rock fracture propagation law

In order to analyze the fracture propagation law of an Ordovician sedimentary rock under uniaxial compression,the deformation of rock surface was studied by using the loading system,VIC-3D observation system and other test systems.The experimental results show that the dynamic evolution of the whole field during the loading process can be obtained by the VIC-3D observation system.The high strain region of the digital surface of the rock surface is increasing continuously,the axial micro-cracks of the rock surface start emerging at the elastic-plastic stage.When the stress reaching 18.02 MPa,the extension of the secondary crack and the surrounding crack leads to the complete destruction of the specimen.Considering the effect of the strain rate on the mechanical properties of the rock and the characteristics of strain fields around the crack of the specimens’ surface,the relationship between the strain rate and the crack growth rate around the main crack Ⅰ,secondary cracks Ⅱ,Ⅲ and Ⅳ are analyzed,and it is found that the fracture rate and the axial strain rate exhibit a strong exponential function correlation.The results of this study reveal the law of the expansion and extension of the Ordovician carbonate sedimentary rocks,which is of great practical significance for the prevention and control of dynamic hazard in coal mine.