Simulation analysis of mechanical response and failure mechanisms of maize stubble-soil composite based on discrete element method and fiber bundle model

The interaction between agricultural machinery, root systems, and soil is crucial for root-soil mechanics and farmland conservation. However, existing studies have rarely explored the fine-scale simulation of crop root failure processes. Analyzing complex root fracture processes and failure mechanisms using discrete element method (DEM) still has certain limitations. This study develops a discrete element model of the crop stubble-soil composite (SSC) based on soil characteristics in arid and cold regions and maize root distribution. Additionally, the fiber bundle model (FBM) is applied to explain the root system’s progressive failure mode and stress distribution. The results show that the SSC model accurately represents the root-soil mechanical response and failure characteristics under external loading. The failure probability of root segments and cumulative failure probability follow Gaussian probability density function and cumulative distribution function, respectively, consistent with the statistical characteristics of fiber failure described by the FBM. Root particle bond rupture shows staged failure behavior, with the basal anchorage zone being most prone to concentrated fracture failure. The root functional zone exhibits a progressive failure process, while the bottom elongation zone demonstrates better stress dispersion and slippage failure. Under external loading, soil particle stress feedback generally lags behind root failure. This study provides a refined modeling method for root-soil mechanical behavior during agricultural equipment operations, and introduces a computational method based on FBM theory to elucidate the mechanisms of root failure during the composite disturbance process, with potential applications in tillage protection and root-soil stability studies.