Effect of particle shape on liquefaction and Re-liquefaction strength of short fiber-reinforced sand

Fiber-reinforcement is a widely studied soil stabilization technique, yet certain aspects of its reinforcing mechanisms and fiber-soil interactions remain unexplored. This research investigates the dynamic behavior of fiber-reinforced soils, focusing on the interaction between fibers and soils with varying angularities and physical properties. Liquefaction and re-liquefaction behavior of unreinforced and fiber-reinforced Mikawa sand of different angularities were evaluated through a series of cyclic triaxial shearing tests. The results are analyzed using liquefaction strength curves and a newly proposed index, N DA - N e , which quantifies strain development during liquefaction. The findings indicate that fiber-reinforcement not only mitigates liquefaction but also suppresses strain development after liquefaction, with greater effectiveness observed in denser specimens within an analyzed range of density. Moreover, the reinforcing effect was higher in sand with angular particles due to the existence of a higher number of contact points with fibers, which creates a more stable soil-fiber matrix. Regarding fiber-sand interaction mechanisms, fibers appear to reduce the initial anisotropy of granular materials, resulting in the promotion of more symmetric strain development in compression and extension. However, re-liquefaction test showed that independently of the stress history from the first series of cyclic shearing, fibers might not be effective in preventing secondary liquefaction due to re-orientation (development of high anisotropy) of the soil matrix during cyclic shearing and weakening of contacts between fibers and sand particles.