Comparative study on cyclic behavior of marine calcareous sand and terrigenous siliceous sand for transportation infrastructure applications

Calcareous sand has been used as an emerging unbound granular filler to replace siliceous sand in the construction of marine transportation infrastructure. However, the critical feasibility of and differences between using calcareous sand as a filler instead of siliceous sand have yet to be suitably assessed. In light of this, this paper presented a comparative study on the cyclic behavior of calcareous sand and siliceous sand through a series of high-cycle drained triaxial tests. To facilitate comparison, the same grain-size distribution and relative density were used for calcareous sand and siliceous sand to investigate any underlying cyclic behavior divergence caused by their respective distinctive particle shapes and breakage. Owing to the irregular and rough properties of calcareous sand particles, results showed that it exhibited stronger shear strength and resistance to permanent deformation than siliceous sand. However, during the early and middle stages of cyclic loading, the accumulation rate of permanent strain in calcareous sand was found to exceed that of siliceous sand due to its violent particle breakage habit, whereas a more severe dilatancy of calcareous sand induced by irregular particle shape was observed during the subsequent loading stage. Moreover, particle shape and particle breakage were found to have different competitive contributions to the increase of resilient modulus during different loading stages. In this work, the allowable cyclic strength ratio capable of better determining the suitable load level for a practical design was suggested. Furthermore, to capture the particle breakage extent under long-term cyclic loads, a refined hyperbolic equation was projected to model the relationship between relative particle breakage index and plastic work.