A steel joint for driven precast concrete geothermal energy pile foundations

Abstract

This invention describes a steel joint used for connecting two precast concrete driven energy pile (DEP) segments which is known as DEP joint. Precast concrete DEPs are cast in segments with a maximum length of 12 m at a concrete factory. DEPs are typically driven into the ground until bedrock; hence, in places where the bedrock is deeper than 12 m, two or more segments must be connected using a joint to produce longer energy piles. DEPs have not been frequently used because no suitable joint existed that could maintain structural integrity and provide leak-proof coupling between the pipes at the joint interface. The present invention addresses this problem by designing a steel joint that can meet the structural and hydraulic requirements of a suitable steel joint for DEPs. Each quadratic concrete energy pile segment is prefabricated in a concrete factory, where the heat transfer pipes are embedded inside the steel cage of each segment. The steel DEP joint is installed at one or both ends of each concrete segment, and has two or four sidewall channels, depending upon its size. Heat transfer pipes are coupled between every two segments, inside the sidewall channels, while the energy piles are installed at a construction site. The sidewall channels are protected using steel shielding plates that are riveted to the joint so that the pipes and the coupling inside the sidewall channels are protected against harsh frictions during the installation of the DEPs in the ground. The steel joint facilitates the installation of longer precast concrete energy piles up to the bedrock depth, especially in sites where the bedrock is deeper than a single segment length. The main advantages of precast concrete energy piles compared to cast-in-place piles are that they enable better quality control and quality assurance, as well as being easier, faster, and cheaper to install. The invented DEP joint has passed structural integrity tests as required according to the BS EN 12794 standard, and also passed hydraulic pressure tests according to the ASTM F2164 – 21; hence, it is certified to be used in construction projects. We are now looking for potential licensees to start manufacturing the joints and using them in the energy pile industry.