## 4 Model Validation and Parametric Study  
To validate the proposed mesoscale computational approach, a numerical simulation of a uniaxial compressive test and a triaxial compressive test was performed. The simulation of the uniaxial compressive test is used to show the evolution of the SRM under loading, and the simulation of the triaxial compressive test is used to compare our model results with previous published experimental results.  
For the simulation of the uniaxial compressive test, a numerical model with a diameter of 0.05 m and a height of 0.1 m was established. The rock content of the generated SRM structure was set as 15%. The Young's modulus of the rock particles and soil matrix was assumed as 3000 MPa and 50 MPa, respectively. The maximum tensile strength and the maximum compressive strength of the rock particles were set as 8 MPa and 90 MPa, respectively. The internal friction angle of the rock particles and soil matrix was set as 50\({}^{\circ}\) and 25\({}^{\circ}\), respectively, and the cohesion of the soil matrix was set as 100 kPa.  
For the simulation of the uniaxial compressive test, the elements on the top and bottom of the sample were fixed in the vertical direction but could move freely in the horizontal direction. The simulations assumed a loading displacement increment of 0.005 m/step. The evolution of the soil-rock distribution, von Mises stress, and accumulated damage are shown in Figure 7. Figure 7 shows that the proposed mesoscale computational approach  
Figure 6: Flowchart of the mesoscale computational approach.  
captured the breakage of rock particles during the uniaxial compressive test. The results show that, in the SRM structure, the rock particles bear the majority of the load, and the stress concentration phenomenon is observed at the edge of the rock particles. Due to the stress concentration, large rock particles break down into several smaller rock particles, and the stress is redistributed. In addition, the damage process of the soil matrix is also defined in the simulation of the uniaxial compressive test. Once a soil element is damaged, it will deteriorate and become a weaker element with a smaller Young's modulus.  
A simulation of a triaxial compressive test was performed to validate the proposed computational approach. The experimental results of a SRM sample with rock contents of 30% were used to validate the simulation field [24]. Samples with a diameter of 0.1 m and height of 0.2 m were used in the triaxial compressive test. The triaxial compression test was conducted at three different confining pressures, namely 100 kPa, 200 kPa, and 300 kPa. In the simulation, the size of the model was adjusted to the same size as the experimental samples. Because the mechanical properties such as the Young's modulus, friction angle, and internal cohesion of rock particles and soil matrix are not mentioned in the reference, the mechanical properties used in the simulation were calibrated by trial and error. The stress-strain curves from the numerical simulation and experiment are presented in Figure 8. The simulated stress-strain curve is in good agreement with the experimental stress-strain curve under different confining loadings. In addition, compared with the  
Figure 7: Evolution of the material distribution, von Mises stress, and accumulated damage of the uniaxial compressive strength.  
experimental results, the stress-strain curve of the numerical simulation shows oscillatory behavior, which is due to the redistribution of stress caused by the breakage of the rock particles under loading.  
In summary, the numerical simulation results of the uniaxial and triaxial tests indicated that the proposed mesoscale computational approach could capture the mechanical behavior of SRMs and characterize the grain-crushing process of SRMs under loadings.