Effects of gradation and grain crushing on the liquefaction resistance of calcareous sand

The dynamic behaviors of calcareous sand were investigated under undrained conditions using cyclic triaxial tests, and the results were compared with those of commercially available Fujian (Fj) sand. The test results were used to evaluate the effects of gradation, particle crushing, and other parameters on the liquefaction resistance. The results of the undrained cyclic triaxial tests indicate that the liquefaction resistance of the well-graded calcareous sand specimens is higher than that of the poorly graded and gap-graded specimens and that the excess pore pressure ratio of calcareous sand cannot reach 1.0. Furthermore, calcareous sand has a much higher liquefaction resistance than Fj sand; this difference is due to the different particle structures and compositions of the two sand types. The particle breakage of calcareous sand was clearly observed after the experiments. To explore this further, the microscopic structure of the calcareous sand was investigated by computed tomography (CT), and inner pores were observed in the calcareous sand particles. A relationship between the liquefaction resistance and particle crushing was determined, which provides direct evidence to explain the process of desaturation observed in some cases.

Automated summary

The dynamic behaviors of calcareous sand were examined through undrained cyclic triaxial tests, showing that well-graded calcareous sand specimens have higher liquefaction resistance compared to poorly graded ones. The presence of inner pores and particle breakage in calcareous sand contribute to its superior liquefaction resistance. Additionally, computed tomography analysis revealed the relationship between liquefaction resistance and particle crushing, offering direct evidence for desaturation processes in some cases.