On the efficiency of the modified smooth joint model for simulating shear behavior of rock joints: A comprehensive experimental-numerical study

The Modified Smooth Joint (MSJ) model offers a robust approach for investigating the shear behavior of rock joints within a discrete element framework where joint profiles are explicitly simulated by applying SJ contacts. Although the model is widely used, its efficiency remains underexplored due to limited experimental validation. Previous assessments have predominantly focused on idealized saw-tooth joints, often overlooking the inherent complexity of natural joints. This research evaluates the MSJ model’s capability to simulate the shear behavior of rough rock joints through an integrated experimental–numerical investigation, addressing two fundamental questions: (1) To what extent can the model replicate the shear behavior of physically identical rough joints? and (2) Which roughness profiles better represent the shear behavior of natural rock joints, considering that multiple two-dimensional profiles can be extracted from their inherently three-dimensional rough surfaces? A novel Joint Dilatancy Checking approach was introduced to mitigate unrealistic dilation at failure associated with conventional calibration methods. More than 80 roughness profiles were simulated and compared against corresponding laboratory tests to obtain statistically meaningful outcomes. The findings indicate that the model accurately predicts the peak shear strength and dilation of identical concrete joints, outperforming Barton’s empirical model in some cases, although it tends to underestimate residual shear strength. The model correctly simulates key asperities mobilized in shear and main damaged areas. Results also demonstrate that the simulation’s efficiency is highly sensitive to profile selection. Incorporating rougher profiles significantly reduced peak shear strength and dilation simulation errors from over 20% to less than 5%.