岩石PFC^(2D)模型细观参数确定方法研究

Study on determination micro-parameters of rock PFC^(2D) model

目前对标定方法的应用大多围绕单轴压缩试验展开,而仅通过单轴试验建立的数值模型在拉伸强度和强度包络线方面与实际试验吻合度较差。因此基于单轴压缩试验、单轴拉伸试验和三轴压缩试验,采用正交试验设计方法对平行黏结模型细观参数标定方法进行了研究。利用多因素方差分析确定了模型细观参数对宏观力学指标的影响程度,并建立了宏观力学参数与细观参数之间的关系。在此基础上提出了与岩石弹性模量、泊松比、单轴抗压强度、启裂强度、拉压强度比及摩擦角相匹配的细观参数确定方法。研究结果表明:采用标定方法建立的数值模型的宏观力学参数以及单轴压缩应力-应变曲线与室内试验结果相近,能够很好地反映岩石单轴和三轴条件下的破坏模式,证明了标定方法的可行性。二维颗粒流程序PFC^(2D)对试验极限主应力关系曲线的拟合程度较差,这可能是由于平行黏结模型将形状不规则的矿物颗粒理想化为圆形颗粒,而颗粒形状可能会影响到颗粒间的咬合作用。

The majority of contemporary numerical model calibration methods focus on the usage of uniaxial compression tests,however the results of numerical models calibrated in this manner are generally inconsistent with the results of actual physical experiments with regards to the tensile strength and strength envelope.Therefore,based on the uniaxial compression test,the uniaxial tensile test and the triaxial compression test,the orthogonal experimental design method was used to study the calibration method of the mesoscopic parameters of the parallel bonding model.The multi-factor analysis of variance was used to determine the degree of influence of the model meso-parameters on the macro-mechanical indexes,and the relationship between the macro-mechanical parameters and the meso-parameters was estab⁃lished.On this basis,a determination method of meso-parameter matching with rock elastic modulus,Poisson′s ratio,uniaxial compres⁃sive strength,crack initiation strength,tensile-compression strength ratio and friction angle was proposed.The research results show that the macroscopic mechanical parameters and the uniaxial compressive stress-strain curve of the numerical model established by the calibra⁃tion method in this paper are similar to the laboratory test results,which can well reflect the failure mode of the rock under uniaxial and triaxial conditions.The PFC^(2D) fits the experimental limit principal stress curve poorly,which may be due to the fact that the parallel bond⁃ing model idealizes the irregularly shaped mineral grains into round grains,and the grain shape may affect the inter-grain occlusion.