Numerical Study on Anisotropic Influence of Joint Spacing on Mechanical Behavior of Rock Mass Models under Uniaxial Compression

Abstract

Mechanical properties of rock masses are dominated by the nonlinear response of joints and their arrangement. In this paper, combined influences of joint spacing (s) and joint inclination angle (β) on mechanical behavior of rock mass models with large open joints under uniaxial compression were investigated by PFC modeling. With a large amount of local measurement circles placed along the pre-defined measurement lines (ML), stresses and joint response parameters at different scales (the measurement circles, the MLs and the whole specimen) were defined and calculated. It was found that macroscopic behaviors of the jointed specimens, such as four types of deformation behaviors, four failure modes, strength, deformability modulus and ductility index, are dominated by nonlinear response of the joint system, especially the interaction between the joints and rock bridges. The joints may experience three stages, i.e., starting to close, closed and opening again. On the joint plane, the peak stresses of the rock bridges and those of the joints may not be reached at the same time; i.e., joint strength mobilization happens with the loss of the rock bridges’ resistance. The influence of s on specimen behavior is little for β = 90°, obvious for β = 0° or 30° and significant for β = 45° or 60°, and this can be related to their different microscopic damage mechanisms.

Study on the size effect of elastic modulus of rock considering the joint spacing

“…This paper proposes a relationship between E and PJS and optimizes its parameters by considering the size change. In existing research, scholars mainly focused on the influence degree (Yang et al, 2019b) (Huang et al, 2019), the influence effect (Chen et al, 2020), and the nonlinear change (Xiong et al, 2019) of the joint parameters. However, they rarely considered the size influence, obtained a relationship for E, or discussed the influence of PJS.…”

“…Yang et al (2019b) and Huang et al (2019) investigated the influence of joint parameters on E and indicated that joint dip has the greatest effect on E, followed by joint length. Chen et al (2020) discovered that E is affected by the interaction of joints and rock bridges through the study of joint dip and spacing. Cao et al (2018) reported that joint inclination mainly impacts E. Xiong et al (2019) proposed a power function to characterize the nonlinear change of E and joint index.…”