Model test study of augered piling of screw displacement auger in sand

Aiming at the impact of augered piling on ground soil, model tests on augered piling of screw displacement auger in homogeneous sand are conducted by self-designed visualization model device. The mechanism for development of borehole is discussed. The displacement behaviors and stress development of soil nearby the borehole are analyzed in macro-scale during augered piling. The mesomechanism of interaction between auger and soil is studied by evolution of sand micro-fabric parameters. The model test results show that impact of augered piling on ground soil depends on vertical stress. The higher the vertical stress is, further the radial displacement in the soil transfers. Radial displacement of soil is mainly within 2.5 times of the auger diameter, accompanying with the significant hoop shear displacement of soil nearby the borehole. The soil nearby the borehole experiences the process of loading-unloading-loading. The sand particles in the area that auger contact width is approximately 5times of the average particle diameters occur significant rotation. The point contact between sand particles and auger develops gradually surface contact with the evolution of isotropy on micro structure. The study results have some significance to disclose the mechanism of augered piling and macro-meso mechanical properties of soil nearby the borehole for the soil displacement screw pile.