In this study, a series of undrained multidirectional cyclic simple shear tests were conducted using the discrete element method. Various stress paths, including figure-8, circular, teardrop, and straight-line shapes, were considered. Realistic and irregular particles were generated by integrating the theory of random fields for spherical topology with the Fourier-shape-based method. The influence of particle shape irregularity was assessed using a synthetic parameter derived from four common descriptors: aspect ratio, roundness, convexity, and sphericity. The study revealed that the liquefaction resistance of samples subjected to a constant cyclic shear stress ratio predominantly depended on the stress trajectory and particle shape. Numerical results demonstrated that the sample undergoing the unidirectional simple shear exhibited the highest liquefaction resistance, whereas the figure-8 shape exhibited the lowest. Furthermore, greater irregularity in particle shape corresponded to increased resistance to failure. Additionally, microstructural evolutions of granular samples were quantified throughout the simulation using the contact-normal-based fabric tensor. This allowed for a comprehensive exploration of the interplay between internal structure and external loading, leading to a more comprehensive understanding of the macroscopic observations discussed above.
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