Abstract
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.
Highlights
With the development of China’s infrastructure construction, it is inevitable that more and more hydraulic, traffic and tunneling structures are built on or in the engineering geological body of the soil-rock mixture (SRM) [1]
Many early experimental investigations were conducted to focus on shear behaviors and its influencing factors of SRM, which can be categorized in two aspects: composition and structure
To accurately describe the resilient characteristics of the soil-rock mixture, the purpose of this study is to carry out laboratory tests to evaluate the resilient characteristics of SRM considering the effect of rock content, and to establish a numerical model to analyze the meso-mechanism of the crushed rocks related to the resilient behavior and anisotropy
Summary
With the development of China’s infrastructure construction, it is inevitable that more and more hydraulic, traffic and tunneling structures are built on or in the engineering geological body of the soil-rock mixture (SRM) [1]. There is a clear gap between the rock blocks and soil matrix in particle size and material. Materials 2020, 13, 1658 composition, so it shows two extreme characteristics in the mechanical properties, that is, the rock mass is highly rigid, while the soil particles are soft and hard. Due to the heterogeneous structure of SRM, its mechanical properties depend on these structural characteristics (compositions, density, strength, etc.) and degree of bonding in the matrix, resulting in a significant difference from natural rocks or soils. Other rock characteristics, such as rock content (Rc ), shape, porosity, gradation and distribution, contribute significantly to the deformation mechanism and anisotropic behavior of granular materials [3,4].
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