Influence of number of load cycles on the resilient response of soils under repeated load triaxial tests

Over the course of its useful life, a pavement structure is subjected to a large number of load cycles, being exposed to varied and broad stress states, and thus establishing a stress history relative to each material. So, the study and understanding of the influence of the number of load cycles on the mechanical behaviour of unbound materials, especially on the resilient response of soils, is fundamental for appropriate pavement design and management. In this context, this paper studied the mechanical behaviour of three soils as pavement materials, focusing on evaluating the effects of number of load cycles on their resilient response. Comparative analyses were performed with experimental data and regression models obtained from resilient modulus and permanent deformation (single-stage and multi-stage) tests using the repeated load triaxial equipment. Moreover, the experimental program also covered the variation of compaction energy and moisture, allowing to analyse the correlation between these variables and the influence of number of load cycles. The results reveal two main trends and discussions. Firstly, in cases where similar resilient values and models were obtained from the tests, there is a suggestion to combine both tests for more efficient laboratory analyses. In other cases, a significant increase in resilient values was observed in permanent deformation tests, attributed to a hardening effect, raising discussions regarding the consideration of resilient modulus results obtained through this test in mechanistic-empirical pavement design, as they may better represent field conditions.