An innovative steel joint for driven geothermal energy piles-Paper

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The paper presents an innovative steel joint that enables precast concrete pile segments to function as driven geothermal energy piles. These piles can provide building foundations while exchanging heat with the ground through embedded fluid pipes, offering an alternative to cast-in-place energy piles, which require extensive drilling and on-site construction.<br /><br />Precast pile segments are manufactured under controlled factory conditions, but transport regulations generally limit their length to about 12 metres. Longer piles therefore require joints. Conventional welded connections can be slow and vulnerable to poor site conditions. The new Driven Energy Pile (DEP) joint uses steel pins to connect segments quickly and securely. Sidewall channels accommodate couplings between the heat-transfer pipes, while a riveted steel cover protects the pipes from damage during pile driving.<br /><br />The joint and pipe connections were tested for structural performance and leak resistance. In accordance with the relevant standard, connected pile specimens underwent 1,000 impact blows at a stress level of 28 N/mm², followed by bending tests. The pipe system was also hydrostatically tested at 100 psi for four hours. No leakage or damage was observed, and the pressure remained within the accepted limit.<br /><br />The results indicate that the DEP joint can transfer axial and bending loads while maintaining protected, leak-proof connections between pipe loops. It offers a practical way to connect factory-made concrete pile segments on site and expand the use of driven precast piles for geothermal heating and cooling.

Keywords

driven energy pile

precast concrete pile

geothermal energy

steel joint

pile segment

pipe connection

hydrostatic test

bending load

axial load

heat transfer pipes