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When a material is subjected to cyclic loading, there are changes in the material's geomechanical behaviour that need to be characterized for a safe design. For unbounded granular materials, the shakedown theory is used to explain the soil's behaviour under cyclic loading. However, it is not clear yet if such theory is extendable to unreinforced and fibre-reinforced stabilized soils. To this end, a series of unconfined compression cycling loading tests were performed, to study the effect of the number of cycles and initial deviatoric stress level on the behaviour of an unreinforced and reinforced stabilized soil. The results were analysed in terms of shakedown theory, elastic and plastic deformation energy and damping ratio. It was observed that shakedown theory seems to represent the behaviour of the stabilized unreinforced and fibre-reinforced soils under cyclic loading, with threshold between the plastic shakedown and the plastic creep shakedown behaviour at around an absolute axial strain 1 × 10–3. The effect of increasing binder content (from 12 to 39%), comparable to reducing the initial deviatoric stress level (from 85 to 15%), promoted a reduction in plastic deformation (from 2.09 to 0.19% without fibres, and 2.21 to 0.24% with fibres) and damping ratio (from 25.17 to 10.01% without fibres, and 29.18 to 15.95% with fibres) due to the lower degradation of the solid matrix. It also promoted an increase in the difference between elastic and plastic energy (from − 1.04 to 13.92 kJ/m3 without fibres, and − 1.68 to 10.19 kJ/m3 for the first cycle). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]