A novel joint for driven concrete geothermal energy pile foundations

Abstract

Geothermal energy pile foundations are among the most common types of energy geostructures which provide both structural support and can be used as a source with ground source heat pumps for heating and cooling buildings. Energy piles can be categorized into cast-in-place and precast piles. Driven precast concrete energy piles can be installed up to the bedrock level, with higher quality, lower cost, and faster installation process, compared to cast-in-place energy piles. Precast concrete driven energy pile foundations have not been commonly utilised due to existing problems with a suitable type of joint that could connect precast segments and allow continuity of heat exchanging pipes. An innovative and novel steel driven energy pile (DEP) joint is presented in this paper which can provide structural integrity between the segments and leak-proof coupling between the heat exchanging pipes. Both sizes of DEP joints passed 1000 impact blows of 28 MPa, they remained undamaged during the bending tests with a flexural stiffness of 3500 kN.m2, and 7720 kN.m2 for the 267 mm and 350 mm joints, respectively. Additionally, the pipes used in the prototype joints and piles indicated no leakage or pressure drop in the hydraulic pressure tests subjected to 690 kPa pressure.