Effect of the Number of Loading Cycles on the Behavior of a Stabilized Fiber-Reinforced Soft Soil: Energy Evaluation

Abstract

When a material is subjected to cyclic loading, there are changes in the material’s geomechanical behavior that need to be known and characterized for a safe design. To this end, a series of unconfined compressive strength (UCS) tests was performed, with and without the application of cyclic loading, to study the effect of the number of loading cycles on the behavior of a soft soil stabilized with different binder contents, unreinforced and reinforced with polypropylene fibers. The results were analyzed in terms of the evolution of elastic and plastic deformation energy, and it was observed that plastic energy prevailed in the first cycles, but decreased with the increase in the number of loading cycles. The accumulated plastic deformation occurring during the cyclic loading induced a strain-hardening effect that was responsible for the increase in the undrained resilient modulus and in the postcyclic unconfined compressive strength, regardless of the binder content and fiber reinforcement. The addition of polypropylene fibers led to a reduction in the elastic deformation energy, which was more noticeable in the first cycles, leading to an increase in the accumulated plastic axial strains and to a reduction in the undrained resilient modulus during the cyclic loading. These facts are explained by the high compressibility of the fibers and by the weakening of the stabilized matrix as a result of the physical presence of the fibers which may prevent the development of some cementitious bonds. However, the addition of fibers led to an increase in the energy absorption capacity, explained by the fact that the deformations occurring during the cyclic loading allow an earlier mobilization of the fibers as the UCS test proceeds.