应力路径对砂岩真三轴变形宏细观特征影响

Effects of stress path on true triaxial macro and micro deformation characteristics of sandstone

为研究应力路径对岩石真三轴变形宏细观特性的影响,利用离散单元法建立标定的颗粒流数值试件,选取加载平面为子午面、π平面和定轴面,对数值试件进行不同应力路径的加载试验,从宏细观角度分析岩石真三轴变形演化规律,并将数值模拟结果与D-P屈服准则进行对比,验证结果的正确性。研究结果表明:相同的应力增量条件下,沿对称加载面加载时,应变增量各向异性最小;沿π平面加载时,应力最快到达屈服面,产生最大的应变,所有应力路径加载过程中,定轴双向卸载产生的应变最大。利用应力空间和屈服面的相对成像、定义变形各向异性参数分析模型试样弹塑性变形特征。从细观层面对应力和应变增量路径的相关性进行定量分析,得出接触力链转化数和应变增量偏角呈负相关,沿π平面加载时,数值模型内部产生最多的微裂纹数目,内部损伤最明显,沿定轴面加载时,产生最少的微裂纹数目,内部损伤最小。

In order to study the influence of stress path on the true triaxial macroscopic and mesoscopic deformation characteristics of rocks,a calibrated granular flow numerical specimen was established using the discrete element method,and the loading planes were selected as meridian plane,π-plane and the fixed-axis plane.Numerical experiments with different stress paths were conducted on the numerical specimen to analyze the true triaxial deformation evolution of rocks from the macroscopic and mesoscopic viewpoints,and the numerical simulation results were compared with the D-P yield criterion to verify the correctness of the results.The research results showed that:for the same stress increment,the anisotropy of strain increment was the lowest when loading along the meridian plane,and the stress reached the yield plane fastest when loading along theπ-plane,resulting in the largest strain increment and the two-way unloading in fixed-axis plane produced the largest strain increment in all stress path loading processes.The elastic-plastic deformation characteristics were analyzed using the relative imaging of stress space and yield surface,defining deformation anisotropy parameters;the correlation between stress and strain increment paths was quantitatively analyzed at the mesoscopic view level,and it was concluded that the number of contact force chain transformations and strain increment de flection angle were negatively correlated,and the numerical model produced the largest number of microcracks with the most obvious internal damage when loaded along theπ-plane,and the smallest number of microcracks with the least internal damage when loaded along the fixed-axis plane.