非均质性对岩石宏观力学特性的影响机制

Influence Mechanism of Heterogeneity on Mechanical Properties of Rock Materials

岩石材料具有材料强度分布不均匀性和材料空间组构随机性的双重特性,从本质上看两种特性都属于岩石材料的非均质性,都对岩石力学性质有深刻影响。在以往的研究中,通常使用有限元法和Weibull分布函数模拟岩石材料强度的非均质特点,用变异系数定义非均质度的大小,得到非均质度与岩石强度力学特性之间的关系,缺少了对材料组构随机性的探索。使用DDA方法和正态分布函数建立非均质脆性岩石单轴压缩数值实验模型,研究了非均质度和材料组构对岩石强度的影响。研究结果表明:随着岩石非均质度的增大,岩石的极限承载力减小;岩石中两接触单元的弹性模量差异越大,应变差异越大,接触面成为易发生破坏的力学薄弱环节。在相同非均质度的岩石样本中,不同组构的样本力学薄弱环节分布不同,导致岩石破裂路径和力学特性也不相同。

Rock materials are featured with nonuniform material strength distribution and random material space fabric,both,in essence,belong to the heterogeneity of rock materials,having a profound impact on the mechanical properties of rock.In previous studies,the heterogeneity of rock material strength was usually simulated using finite element method and Weibull distribution function,and the relationship between heterogeneity and rock strength mechanical properties was obtained by defining the degree of heterogeneity with the coefficient of variation,which lacks consideration of the randomness of material fabric.In this research,a numerical model for the uniaxial compression test on heterogeneous brittle rock was established using the DDA(Discontinuous Deformation Analysis)method and the normal distribution function.The effects of heterogeneity and material fabric on rock strength were examined.Results demonstrated that with the growth of rock heterogeneity,the ultimate bearing capacity of rock attenuated.The greater the difference of elastic modulus between two contact elements in rock,the greater the strain difference,and the weaker the mechanical properties of the contact surface.In rock samples of the same degree of heterogeneity,the distribution of the weak points differs with fabrics,resulting in different rock fracture paths and mechanical properties.