Frequency effect on mechanical properties of calcareous sand under cyclic traffic loading

Abstract

Calcareous sand is an essential material for building airports in the South China Sea. Frequency plays an important factor in the dynamic properties of calcareous sand. However, most of the related studies adopted cyclic triaxial tests and impractical loading paths and showed contradictory results. This paper summarizes the potential reasons for the conflicting conclusions, and analyses the mechanical behavior of three types of samples, including unstable, metastable, and stable situations under cyclic traffic loading with Hollow Cylinder Apparatus. This research proposed a new method to clarify the sample stability under cyclic stress ratios with different frequencies and found that resilient porewater pressure (pwpr) can be more appropriate than other commonly used parameters e.g. strain, porewater pressure, and dissipation energy. The pwpr also correlates with the particle morphology of calcareous sand, which with more irregular morphology leads to greater sensitivity to loading changes. The results indicate that higher frequency stabilizes the samples regardless of cyclic stress ratios. Considering the frequency effect, the paper gives related functions and simulates cumulative axial plastic strain variations and elastic modulus against cycle numbers for stable samples.