Discrete element modeling and experimental validation of arch-induced density heterogeneity in compressed mushroom residue

To investigate the arching effect as the primary factor contributing to density distribution irregularities during the compaction process of shiitake mushroom residue, this study systematically investigates the existence and evolution mechanisms of arch structures by integrating carbon paper indentation experiments with Particle Flow Code in 2 Dimensions discrete element simulations. Unlike previous studies focusing solely on macrostructure or force chain morphology, this work innovatively adopts a microscopic statistical approach, revealing for the first time the intrinsic connection between the evolution of the contact force distribution and the development of the arching effect. The study reveals that the three stages of arching evolution are accompanied by systematic transformations in the contact force distribution of the granular system: transitioning from an initial long-tail (power-law) distribution to a normal distribution, and then re-approaching a compacted normal distribution during the arch reorganization stage. Additionally, the study examined the influence of macroscopic discrete element method parameters on arch formation, revealing that the sidewall friction coefficient plays a decisive role in arch development, while the loading rate primarily affects the timing of its formation.