Centrifuge Modeling Methodology for Energy Pile Pullout from Saturated Soft Clay
Ismaail Ghaaowd, John S. McCartney
Abstract
ABSTRACT This paper describes a test setup and methodology for centrifuge modeling of energy pile pullout from saturated soft clay, with the goal of understanding how pile heating improves the interface shear strength through thermal consolidation. A kaolinite clay layer was first consolidated outside the centrifuge within a cylindrical container with an inner diameter of 551 mm using a hydraulic piston to reach a thickness of 220–240 mm then permitted to equilibrate in the centrifuge under 50 g. An aluminum energy pile having a model-scale diameter of 25 mm and length of 255 m was then installed at a constant displacement rate through the clay layer and embedded into an underlying sand layer. An electrical resistance heater within the pile was used to heat the soil-pile interface to a target temperature, and thermocouples and pore water pressure transducers in the clay layer were used to track the coupled heat transfer and water flow processes. Detailed results are reported from a baseline test on an unheated pile and from a test on a pile where pullout was performed after heating the pile from 20°C to 65°C and cooling back to 20°C with no head restraint. The pullout capacity of the heated energy pile was 1.43 times greater than that of the unheated energy pile. Insights into the increase in capacity were gained from undrained shear-strength profiles in the clay layers measured using push-pull T-bar penetration tests performed after pullout.