基于内动力的对径压缩岩石拉张破裂演化规律研究

Study on the Evolution of Tensile Fracture of Rock Based on the Brazilian Test Considering Internal Driving Force

岩石是一种复杂的天然非均匀脆性材料,拉压性能差距较大,拉破坏往往控制着岩石工程整体的稳定性.论文将岩石内部某一点在一定尺度范围内所受内力的差异性定义为内动力,进行了对径压缩岩石拉张破裂裂纹扩展实验.采用高速摄像机捕捉破裂瞬时拉张裂纹扩展过程并用数字散斑软件分析第一主应变演化过程.采用连续-非连续方法模拟对径压缩岩石拉张裂纹扩展过程.从实验结果可以看出:拉张破裂裂纹扩展分为三个阶段:拉张破裂变形累计阶段(宏观无裂纹)、拉张破裂裂纹稳定扩展阶段、拉张破裂裂纹动态张裂阶段.将实验、数值计算结果与解析解进行对比分析,实验与数值计算结果扩展规律基本一致,但是与弹性力学解析解不同.解析解基于均匀性假设,而外载荷及岩石本身是非均匀的.外载荷及岩石本身的非均匀性是裂纹起裂点、扩展路径与解析解不相同的主要原因.综合分析给出拉张破裂裂纹扩展规律:当外载荷作用下内动力超过原子或分子连接力则裂纹扩展,扩展方向与内动力的方向垂直.岩石拉张破裂裂纹扩展演化规律的研究可为岩石工程拉张破坏的预防和控制提供理论依据.

As a complex heterogeneous brittle material,rock typically shows lower tensile resistance than compressive resistance.As a result,tensile failure often governs the overall stability of rock engineering.In this paper,the difference of internal forces acting on a certain point within a certain scale in the rock is defined as the internal driving force.The Brazilian disc test was carried out to evaluate crack propagation in rock specimens.The transient tensile crack growth behavior was captured using a high-speed camera,and the evolution process of the first principal strain was analyzed by digital speckle analyzer software.The tensile crack growth process of diametrically-compressed rock discs was simulated using the continuous-discontinuous method.It can be seen from the experimental results that the crack propagation of tensile fracture can be divided into three stages:the cumulative stage of tensile fracture deformation(macro-crack-free),the stable stage of tensile fracture crack propagation,and the dynamic stage of tensile fracture crack propagation.The experimental and numerical results are compared with the analytical solutions.The propagation laws of experimental and numerical results are basically consistent,but are different from the analytical solution of elasticity.The analytical solution is based on the assumption of homogeneity,but the external loads are non-uniform and the rock is heterogeneous,resulting in the crack initiation points and propagation paths different from the analytical solutions.Through comprehensive analysis,the law of tensile crack growth is given:the internal driving force is used to analyze the propagation law of tensile crack.When the internal driving force exceeds the intramolecular forces,the crack propagates along the direction perpendicular to the internal driving force.This study of crack propagation and evolution of tensile fracture can provide a theoretical basis for the prevention and control of tensile failure of rock engineering.