ABSTRACT
Geothermal energy pile foundations can extract and store geothermal energy as a renewable, sustainable, and affordable solution for heating and cooling buildings, besides providing structural support. The majority of energy piles are cast-in-place concrete piles that require drilling which is expensive and time-consuming. Another competitive option is driven energy piles made from precast concrete segments, that are cast in a concrete factory in large quantities and of high quality, then transported and installed on a construction site using innovative steel joints presented in this paper. Apart from providing structural integrity, these steel joints can provide leak-proof couplings for fluid circulation pipes inside sidewall channels, which are shielded using a steel cover plate riveted to the joint. Precast-driven pile foundations can be manufactured from high-strength concrete quadratic segments with 27 cm or 35 cm width, which are assembled via steel joints. There can be one U-loop in 270-mm piles or two U-loops in 350-mm piles. Steel pins connect the joints, and easy couplings connect the pipes quickly. The steel joints presented in this paper provide the opportunity to utilize segmental precast concrete pile foundations as energy piles. Field-scale impact tests and laboratory bending tests were carried out to ensure the piles were not affected by installation and service dynamic forces due to the incorporation of new joints. It was found that the segmental driven energy piles could easily take a minimum of 1000 blows without structural or leakage failure and also demonstrated a satisfactory bending stiffness.
