Mechanical Properties of Similar Materials Simulating Weak Surrounding Rocks with Different Ratios of Fine-to-Coarse Aggregate

The purpose of the study is to provide an optimum RFCA for similar materials simulating weak surrounding rock and to present a convenient and efficient numerical method to determine the optimum ratio of fine-to-coarse aggregate (RFCA) in geo-mechanical model tests. The selection and proportion of aggregates in similar materials significantly affect the mechanical properties of the materials, thereby influencing the results of experiments. Current studies have different opinions on the relationship between the aggregate ratio and the behaviour of similar materials. In comparison to time-consuming, repetitive proportioning tests, discrete element analysis is a convenient method, as most current analyses focus on either highly cohesive materials or non-cohesive materials, ignoring weakly cohesive materials such as similar materials simulating weak surrounding rock. In order to solve this, in this study, several specimens with different RFCAs were created to simulate weak surrounding rock. Uniaxial compression tests were conducted on these specimens, which were simulated by discrete element analysis. Some key parameters were calibrated by comparing the results from the discrete element analysis and the compression tests. Based on the calibrated parameters, the effect of RFCAs on the mechanical properties of similar materials was investigated. Mathematical relationships between the RFCAs and mechanical properties, such as elastic modulus, cohesion, and internal friction angle, were proposed. The variations in particle contact forces and crack propagation patterns in similar materials with different RFCAs were discussed from a microscopic perspective.