基于颗粒离散元模型的岩石蠕变模拟试验

摘要

为了从岩石颗粒之间不连续特征的角度研究其永久变形行为，基于颗粒流理论，采用颗粒离散元方法对微观颗粒之间的接触赋予Burgers模型，进行岩石二维离散元虚拟单轴蠕变试验。采用单因素法研究分析颗粒粒径、摩擦因数、颗粒法向与切向刚度比对流变特性模拟值的影响。从单轴蠕变压缩的轴向蠕变及轴向蠕变速率曲线的离散元模拟值与其解析解对比可以看出：模拟结果与解析解具有较高的吻合性；为更加明确地表示出蠕变不同阶段，选用对数蠕变柔量来进行解析解与模拟值的比对，蠕变初始阶段，PFC压缩模型会低估蠕变柔量，而在稳定蠕变阶段，两者具有高度的一致。数值模拟与解析解结果对比验证颗粒流 Burgers 模型适合用于岩石蠕变试验研究中，可为岩石蠕变的后续深入研究提供有益的参考。%In order to investigate the permanent deformation behavior of rock considering its discontinuous feature, a two-dimension (2D) virtual uniaxial creep test of rock was developed based on the particle flow theory. According to the discrete element method, the micro parameters of Burgers model in particle flow code (PFC) was studied first. The effects of the micro-properties such as the particle radius, friction coefficient and the ratio of particle normal and shear stiffness on its creep behavior were examined using the single factor method. The simulated results of the axial strain and its rate exhibit similar trends to their corresponding analytical results. The main advantage of plotting the creep compliance is that it allows easy identifying of the distinct creep stages. The comparison shows that the simulation results underestimate the creep compliance in the initial creep stage but do a satisfactory prediction in the steady-state creep stage. The correctness of Burgers model in the study of rock creep behavior was verified by the comparison between the simulation and analytical results and it can function as a beneficial reference for further research on the rock creep in PFC.