Effect of groundwater flow on the THM behavior of an energy pile

Bridges are one of the road structures that are most exposed to icing, a problem that is widely dealt with through salting, a technique that reduce the lifespan of the bridge. Seasonal storage of solar heat energy captured directly through the asphalt layer is a promising solution that can be achieved cost-effectively only if a necessary geostructure is used as heat-exchanger. Bridge piles and abutments are founded on piles that can be used as heat exchangers. Seasonal storage and natural thermal reload are two possible solutions for the operation of such a system, depending on local conditions. In particular, the presence of groundwater flow is thought to be a significant factor in such a design and is taken into account. The study aims at determining the geotechnical and energy design parameters through thermo-hydro-mechanical numerical simulations. A single heat-exchanger pile is taken as an example in this study. Given the presence of water flow, a three-dimensional FEM simulation needs to be carried out. The soil is described as a thermo-elastic porous medium, and various groundwater flow scenarios are studied. The capture of energy and the needs for deicing are based on the few existing structures that use other means of energy exchange with the ground. The article proposes an overview of all coupled phenomena, between thermal, hydraulic and mechanical aspects. Results show that only specific sites can be considered for using heat-exchanger piles for deicing bridges, but that the efficiency of the solution in those sites is high. Possible stability problems, in terms of foundation and structure are also considered, such as vertical displacements due to the dual use of the foundation piles.