Numerical Investigation of the Influence of Circular Fillings on the Failure Mechanism in Samples Containing Nonpersistent Joints Under Shear Loading Conditions

In the current research, the influence of filling on the failure mechanism of nonpersistent joints under applied shear stress has been scrutinized using particle flow code (PFC2D). Additionally, the effects of nonpersistent joints on tunnel stability in jointed samples have been investigated. First, to reproduce the concrete specimen, PF2D was calibrated. The modeled samples with dimensions of 100×100 mm were numerically solved. The notch lengths were 15, 10, and 5 mm. The circular filling was situated in the middle part of the model, and the filling diameter was 30 mm. Gypsum materials have been employed to study the filling of modeled samples. The flat joint model was used for calibration. The tensile strengths of the concrete and gypsum samples were 3.4 and 1.4 MPa, respectively. Finally, shear tests were carried out on nine models. A shear load of 0.001 mm/sec was applied until the model’s failure occurred. The results indicated that for fixed notch lengths and under normal loading conditions, shear cracks were induced in the filling layer. The tensile cracks were initiated from the original crack (joint) tips and extended within the model until coalescence with other joints and extended toward the model’s boundaries. The maximum shear displacements accompanied by the shear strengths of the models increased with decreasing joint filling for the fixed notch lengths.