Abstract:

To study the extrusion effect of the press-in method on surrounding soil, the soil displacement field was determined using the semi-model pile test combined with digital image correlation (DIC) technology and horizontal soil stress was measured by mini pressure cells. Firstly, the cumulative displacement of soil was analyzed at different distances from the pile and the changing law of soil stress was recorded during the pile press-in process. Secondly, the final soil displacement was recorded and analyzed when piling was completed. Finally, the disturbance layer was recorded at the pile-soil interface using a local camera, and the thickness of the disturbance layer was measured. Cumulative displacement gradually reached a stable state, and the measure of displacement decreased with distance from the pile. The maximum value of horizontal soil displacement was at a depth of $16R$ ($R$ is the pile radius). The direction of vertical displacement varied with depth. The development of lateral soil stress was considered including the effects of horizontal and vertical displacement. A strong positive relationship was found between lateral soil stress and vertical as well as horizontal soil displacement during the pile press-in process. The results support the development of a squeezing effect caused by the pile press-in process and the mechanism between the pile and the soil.

Key words: digital image correlation technology, pile press-in, soil displacement field, pile-soil interface, disturbance layer