Abstract: According to the mechanical characteristics of a single pile, the full-size pile is proportionally minified. A series of experiments is conducted on the model piles under various vertical uplift static loads, horizontal static loads and vertical compressive static loads, with considering various pile lengths and surrounding sands. Relationship among parameters such as deflection, displacement, axial force and burial depth, grain gradation of surrounding sand is clarified. The influence of loading direction on the bearing capacity of single pile in calcareous sand is explored. Pile-sand interaction mechanism in calcareous sand is analyzed. It is shown that, the displacement and deformation of a single pile vary significantly with the loading direction, burial depth and grain gradation of the surrounding sand. To increase the burial depth is more favorable for uplift pile than for compression pile. The effect of increasing burial depth is more pronounced in the early loading stage, and gradually diminishes as the load increases. When a stepwise load is applied to the top of the model pile, the bearing form alters from side friction bearing to tip resistance bearing. Particle breakage and redistribution can result in a degradation in εmax of uplift pile within the late loading stage. The bearing capacity of a single pile is larger in a wider-grading calcareous sand and the stability of the pile is better in the singleness-size sand. A decrease in side friction of the model pile would occur due to the shear-induced particle breakage in the vicinity of the pile; but at the moment the particles at pile tip crush, an instantaneous reduction in side friction would occur. The research results can provide a guidance for pile optimization, design and construction in calcareous sand.

Key words: calcareous sand, model pile, static loading test, bearing capacity, deformation