Experimental investigation into the effects of polymer/bentonite support fluids on tensile shaft resistance of bored piles
Experimental investigation into the effects of polymer/bentonite support fluids on tensile shaft resistance of bored piles
While synthetic polymer support fluids have emerged as alternatives to conventional bentonite support fluids in piling, their effects on the tensile shaft resistance of bored piles subjected to uplift loading are inadequately understood. In this study, two bored piles with designed length of 4.5 m and diameter of 300 mm were constructed using bentonite and polymer support fluids respectively, in a 5 m deep soil pit filled with uniformly compacted sand, at the National Buried Infrastructure Facility, NBIF. Their tensile performances were tested by loading upward axially and monitored by multiple embedded sensors including distributed fibre optics. Post-testing investigations on pile-soil interface characteristics were carried out by reconstructing digital profiles of the fully exposed concrete piles using 3D laser scanning. It was observed that with bentonite the pile developed a sand-clay filter cake layer, with an average thickness of 10.9 mm, which defined a cylindrical shear surface. In contrast, the polymer pile exhibited a rougher interface between the concrete and sand without filter cakes, with the failure surface represented by a cone of soil near the ground surface and a cylindrical shear below. It was demonstrated that, by using polymer support fluids, a stronger bond between the cast concrete and the surrounding soils was achieved, resulting in ~15% higher in ultimate tensile strength compared to that of the bentonite pile.
Wuzhou Zhai; Anna Faroqy; I. Jefferson; N. Metje; Peter Braithwaite; Kieran Hansard; Sha Q. Luo; Thomas King; Jim DeWaele; Ken Goodhue; Henry Spinks-Essam; Andrew Heathcote; Piotr Konieczny
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Session 3: Resilient geotechnical infrastructure
https://doi.org/10.53243/ICPMG2026-452