Energy Piles in Underpinning Projects - Through Holes in Load Transfer Structures-Article

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The paper examines how geothermal energy micropiles can be incorporated into underpinning projects for existing buildings. Unlike new construction, underpinning requires load-transfer structures that can obstruct the collector pipes running from the piles to the building’s heating system. The FIN-C2M project assessed 13 load-transfer arrangements and found that energy micropiles are feasible in nine; they are generally unsuitable with jet-grouted columns.<br /><br />In five compatible arrangements, pipes can pass directly through the pile cap using methods similar to those used in new buildings. In four others, where jacking occurs directly above the pile, pipes must either exit through the pile’s side before the cap or be accommodated using a specially designed jack system. Steel-beam configurations may also require gaps or modified beams. These solutions need project-specific design, and some remain largely untested.<br /><br />The paper also describes hybrid energy micropiles, which combine structural support with deeper geothermal boreholes beneath the building. Their feasibility depends on site geology, groundwater conditions, building energy demand, and appropriate spacing. Finnish guidance cited in the paper recommends energy piles at least 15 m long and generally 4–5 m apart; hybrid piles are typically spaced at least 15 m apart.<br /><br />Installation and durability require attention. Collector pipes must be protected from damage, and steel piles may need corrosion protection. Concrete can improve heat transfer, while water filling makes pipes easier to replace. The authors conclude that energy micropiles can provide a technically and economically viable renewable-energy option for underpinning, but each project requires individual assessment of structural details, installation methods, thermal performance, and costs.

Keywords

geothermal energy

micropiles

underpinning

load-transfer structures

collector pipes

pile cap

energy piles

hybrid energy micropiles

heat transfer

corrosion protection