Liquefaction of crushable granular media: A multiscale numerical analysis

Understanding liquefaction—the loss of shear resistance in granular materials under constantvolume shearing—is crucial for preventing landslides and geotechnical failures. This phenomenon typically occurs in water-saturated media during rapid undrained loading, such as seismic shocks. Liquefaction potential decreases with higher solid fraction and particle size polydispersity, but evolves if particle fragmentation occurs. We investigate the mechanics and microstructure of crushable, liquefiable granular materials through 2D undrained shear simulations. Results show that higher solid fractions and stronger particles delay liquefaction. Mechanical instabilities manifest as sharp drops in mean and deviatoric stresses, leading to resistance loss and fluid-like behavior. The redundancy number strongly correlates with shear resistance and contact network stability. At high solid fractions, grading upon fragmentation asymptotically approaches an ultimate state while maintaining stability. In contrast, looser samples exhibit earlier liquefaction, with fragmentation depending on particle strength. These findings highlight the critical role of particle strength in either mitigating or intensifying liquefaction.