Model test on deformation characteristic of pile driving in sand using piv technique

A small-scale modeling test system based on particle image velocimetry (PIV) was developed for studying the movement of soil during a pile installation. During the whole process, a charge coupled device (CCD) camera was used to capture images of planar soil deformation. Using PIV, the displacement distributions during a pile installation were then obtained, considering different jacking depths, frictions and pile shoes. The observed displacements were compared with the theoretical predictions of a cavity expansion method, and the law of radical displacements were similar. Thusly, the test system is valid. Comparing with the traditional test methods, it is easy to operate and the non-intrusive technique has a low request to its environments. The test results showed that for a flat-ended pile, its influence zone was 8R around the pile shaft and 4R below the pile tip; when shaft friction was considered, the observed influence radius was 2R larger around the pile shaft but has little effect below the pile tip. Meanwhile, for a pile with a shoe angle of 45°, the displacement around the pile shaft was higher, but the vertical movement below the pile tip was much lower, compared with the flat-ended pile; when shaft friction was considered, the observed displacement was almost identical.