Energy piles in underpinning projects – through holes in load transfer structures

Abstract Energy piles are fairly new solutions and have gained significant traction around the globe. Since the twenty-first century, geothermal energy collector pipes are being frequently installed, finding its most common implementation in newly constructed buildings. Much less studied is the application of energy piles in existing buildings and older constructions. The biggest challenge in the utilization of energy micropiles in underpinning projects is related to the through holes for geothermal energy collector pipes in the load transfer structures. In the FIN-C2M project (Case 2 Micropile Research Project in ISM collaboration), several technical solutions were investigated to identify the most suitable options to accommodate the utilization of energy micropiles with minimum interference of the load transfer structures. At the moment there are 13 known load transfer structure cases and energy micropiles can be used with nine of them. In general, they cannot be used with jet grouting. In five of the studied cases, the through holes for the collector pipes can be constructed as found in new buildings. In the other four cases, where pretensioning is achieved by jacking directly above the micropile, the construction of through holes requires further development, for which limited suggestions exist, however; the challenge is to bypass the jack. This paper will present all nine cases along with construction details and recommendations for the utilization of energy micropiles in existing buildings.