An Experimental Investigation on the Benefits of a Hybrid Pile/Footing System on Sand-Paper

Paper

Pdf Summary

The study investigates whether attaching a square bearing plate to the top of a driven steel pile can increase capacity and reduce the required pile depth. Laboratory tests used open-ended steel pipe piles driven into dry, loose Leighton Buzzard sand. Three configurations were tested: no plate, a plate twice the pile diameter (2D), and a plate three times the diameter (3D), with three trials per configuration.<br /><br />Compared with the unplated pile, the 2D plate increased capacity by about 20%, while the 3D plate increased it by about 110%. Surface heaving and cracking indicated that the plates acted like shallow footings and compacted the surrounding sand, with greater compaction for the larger plate. The researchers developed a bearing-capacity calculation method that accounts for sand compaction and dilation, and back-analysis produced friction-angle estimates consistent with published values.<br /><br />A hypothetical design example suggested that, for a 2 MN load, a 2D plate could reduce pile depth from 7.8 m to 6.5 m, while a 3D plate could reduce it to 3 m. The authors conclude that this hybrid pile/footing approach could save material, cost, and embodied carbon. However, the evidence comes from small-scale, 1-g tests in a specific dry sand, so full-scale performance and application to other soils and pile types require further investigation.

Keywords

bearing plate

driven steel pile

pile capacity

pile depth reduction

hybrid pile footing

Leighton Buzzard sand

sand compaction

bearing capacity analysis

pile bearing test

embodied carbon