Model tests of single pile vertical cyclic loading in calcareous sand

Pile foundations in calcareous sand are often applied to bear vertical cyclic loads. Model tests of a single pile bearing vertical cyclic loads were performed in calcareous sand, and the accumulated settlement and bearing capacity were measured via sensors using a self-designed experimental device. The influences of the dynamic load and number of cycles on the accumulated settlement and bearing capacity of the pile were analyzed. The results revealed that the accumulated settlement of the pile increased with the number of cycles, it was categorized as either stable, progressive, or destructive. The "threshold effect" was observed once a critical number of cycles had been achieved, the particles breakage hindering the settlement tendency lead to the accumulated settlement rate of the pile gradually decreased and stabilized. During cyclic loading, the proportions of the upper load shared by the pile end and side constantly changed, the pile-side frictional resistance gradually decreased, while the average resistance of pile end slowly increased. After cyclic loading, the bearing capacity of the pile was improved slightly, but the pile-side frictional resistance was greatly reduced, two formulas were presented. The test results can be used for the design of pile foundations in calcareous sand.