*2.2. Calibration of Discrete Element Simulation Parameters of the Peat*

In order to establish a proper model for simulating the compressing process of peat substrate blocks by the DEM method, the parameter calibration of the peat was the prerequisite. The related simulation parameters mainly include the intrinsic parameters of the peat and the contact parameters between the peat and peat as well as between the peat and boundary material (impact recovery coefficient, static friction coefficient, rolling friction coefficient, etc.). The stacking angle referred to the maximum slope angle accumulated and formed on the horizontal surface when particles slowly fell from a certain height under the action of gravity. It was usually taken as the response value, which was mainly influenced by the friction mechanisms between the particles and between the boundaries. Hence, the stacking angle test was performed and reproduced by numerical simulation to determine the optimal parameters of the DEM model.
