Systematic numerical evaluation of the influence joint geometrical and mechanical parameters on the REV of rock masses

The Representative Elementary Volume (REV) is a key concept in the analysis and simulation of jointed rock masses, playing a crucial role in selecting the dimensions of laboratory samples and the domain size of numerical models. However, a precise understanding of the influence of joint geometric and mechanical parameters on the REV remains limited. In this study, the scale dependency of the mechanical properties of jointed rock masses was systematically investigated using three-dimensional numerical modeling. The REV was defined based on the convergence of peak strength and deformation modulus within a 5% threshold. The influence of joint geometric and mechanical parameters on the REV, as well as on the mechanical response at the REV, was analyzed. The results showed that the REV is highly dependent on the loading orientation relative to joint planes, with the smallest values observed when loading is approximately parallel to the joints, and the largest values occurring when the loading direction is favorably oriented for joint sliding and failure. The introduction of a second joint set significantly increased the REV, particularly in modulus-based evaluations. Increasing joint number and spacing enlarged the REV and intensified the reductions in strength and modulus in loading directions that promote joint activation, whereas variations in mechanical properties had a limited influence. It was also found that the deformation modulus is more sensitive to scale than peak strength, requiring larger model sizes to achieve convergence. These findings highlight the importance of joint network geometry in REV estimation and provide practical guidance for selecting representative sample sizes and numerical model dimensions in tunneling, slope stability, and underground excavation projects.