Qian Junfeng, Yao Yongsheng, Li Jue, Xiao Hongbin, Luo Shenping
School of Civil Engineering, Central South University of Forestry and Technology, Changsha 410004, China.
Engineering Research Center of Catastrophic Prophylaxis and Treatment of Road & Traffic Safety of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China.
Materials (Basel). 2020 Apr 3;13(7):1658. doi: 10.3390/ma13071658.
The physical composition and stress state of soil-rock mixture (SRM) materials have a crucial influence on their mechanical properties, and play a vital role in improving the performance of subgrade. To reveal the resilient behavior and mesostructure evolution of SRM materials, triaxial tests and discrete element method (DEM) numerical analysis have been carried out. In the triaxial test section, the mechanical response of SRM materials was investigated by preparing samples under different stress states and physical states and conducting triaxial tests on samples. Simultaneously, a new irregular particle modeling method was developed and applied to the discrete element modeling process to analyze the mesostructure evolution of SRM materials under cycling loading. First, a cyclic triaxial test of SRM material is performed on the SRM material, and the effects of bulk stress, octahedral shear stress and rock content on the resilient modulus of the SRM material are analyzed. It is revealed that the resilient modulus increases with increasing bulk stress and rock content, and decreases with increasing octahedral shear stress. Based on a new resilient modulus prediction model, the relationships among the rock content, stress state and resilient modulus are established. Then, based on an improved DEM modeling method, a discrete element model of the SRM is established, and the influence of rock content on coordination number and mesostructure evolution of the SRM is analyzed. The results show that in SRM materials, the increase of crushed rock changes the mesostructure of the SRM material. With the increase of rock content, the internal contact force changes from "between soil and rock" to "between rocks", and the skeleton formed in the rocks gradually develops overall stiffness. Under the condition of low stress, the anisotropy of the SRM material is mainly caused by the shape and grade distribution of crushed rock. The induced anisotropy caused by the change of stress state has little effect on its mechanical behavior, which may lead to the greater dispersion of multiple SRM test results.
土石混合体（SRM）材料的物理组成和应力状态对其力学性能有着至关重要的影响，并且在改善路基性能方面发挥着关键作用。为了揭示SRM材料的回弹特性和细观结构演化，开展了三轴试验和离散元法（DEM）数值分析。在三轴试验部分，通过在不同应力状态和物理状态下制备试样并对其进行三轴试验，研究了SRM材料的力学响应。同时，开发了一种新的不规则颗粒建模方法并应用于离散元建模过程，以分析SRM材料在循环荷载作用下的细观结构演化。首先，对SRM材料进行循环三轴试验，分析围压、八面体剪应力和岩石含量对SRM材料回弹模量的影响。结果表明，回弹模量随围压和岩石含量的增加而增大，随八面体剪应力的增加而减小。基于一个新的回弹模量预测模型，建立了岩石含量、应力状态和回弹模量之间的关系。然后，基于改进的DEM建模方法，建立了SRM的离散元模型，分析了岩石含量对SRM配位数和细观结构演化的影响。结果表明，在SRM材料中，碎石含量的增加改变了SRM材料的细观结构。随着岩石含量的增加，内部接触力从“土与岩之间”转变为“岩石之间”，岩石中形成的骨架逐渐发展出整体刚度。在低应力条件下，SRM材料的各向异性主要由碎石的形状和级配分布引起。应力状态变化引起的诱导各向异性对其力学行为影响较小，这可能导致多个SRM试验结果的离散性更大。
