Investigating the effect of external forces on the displacement accuracy of discontinuous deformation analysis (DDA) method

Blocks of different sizes are formed in a typical rock mass and affect its stability. The size difference in between the blocks consisting a rock mass is also important from the rock stability point of view. In this paper, the effects of external loading changes on the rock blocks displacements in the DDA method has been studied. The effects of external forces on the stability of the blocky rock mass not only depends on the magnitude of the applied forces but also depends on the dimensions of the blocks constituting the rock mass. In this research, an attempt has been made to examine the effects of centralized external forces on the stability of a blocky system via the definition of the External Force Index. The intensity of its effects on the displacement accuracy with respect to the time step length was analyzed and its relation with the analysis time is also investigated. It has been shown that accuracy of the displacement analysis of horizontal sliding block has an initial disturbance and is a function of the number of time steps, time interval and the EFI. In addition, the relation between the analysis time and EFI has also been studied.