PSI - Issue 84

Arianna Lupattelli et al. / Procedia Structural Integrity 84 (2026) 845–851

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Fig. 4. Temporal evolution over 7 days for the edge pile P1 (black lines) and the central pile P6 (grey lines), recorded at different depths. (a) axial stress; (b) settlements. 5. Conclusions This study explores a sustainable approach to enhance the safety and durability of aging viaducts, addressing environmental and mechanical degradation by proposing low-enthalpy geothermal solutions as an alternative to conventional, environmentally harmful deicing methods. A two-dimensional finite element model was developed to reproduce the coupled thermo-mechanical behavior of a foundation reinforced with energy micropiles (EMPs), which simultaneously provide structural support and exchange heat with the surrounding soil under Mediterranean climate conditions. The results show that EMP foundations can initially meet the high thermal demand for snow-melting, but this capacity is maintained only during the first two days. Afterward, thermal output decreases due to interference, particularly in central micropiles, where overcooling reduces the temperature gradient needed for effective heat exchange. This indicates that continuous snow-melting alone is insufficient for sustained operation, and intermittent operation or active heat pumps may be needed for stable performance beyond two to three days. Thermo-mechanically, snow- melting generates tensile stresses up to 250 kPa, especially in central piles, and thermal contraction increases downward settlement, though these stresses remain small compared to the capacity of steel reinforcement. Overall, retrofitting viaduct foundations with EMPs is feasible, effectively combining structural rehabilitation with pavement temperature control. System performance is highly dependent on operational mode and soil conditions: passive EMPs provide robust summer cooling, while snow-melting requires auxiliary heat pumps to ensure reliable multi-day operation. Acknowledgements Part of this work was carried out within the scope of COST Action CA21156 – “european network for FOstering Large- scale ImplementAtion of energy Geostructure” (FOLIAGE). PRIN2022 Project – “Closing knowledge gaps on energy geostructures for retrofitting of buildings and infrastructures” (GEOREFIT) CUP: E53D23002670006, and CETP 2022 – “Large - scale climate neutral Energy Geostructures in District Heating & Cooling systems/networks” (LEG-DHC) CUP: B97G22000940003 are thanked for the support provided within the numerical activities. The authors gratefully acknowledge FABRE – “Research consortium for the evaluation and monitoring of bridges, viaducts and other structures” ( www.consorziofabre.it/en). References Adl-Zarrabi, B., Mirzanamadi, R., Johnsson, J. 2016. Hydronic Pavement Heating for Sustainable Ice-free Roads. Transportation Research Procedia 14, 704-713. Batini, N., Rotta Loria, A.F., Conti, P., Testi, D., Grassi, W., Laloui, L. 2015. Energy and geotechnical behaviour of energy piles for different design solutions. Applied Thermal Engineering 86, 199-213. Bourne-Webb, P.J., Lupattelli, A., Bodas Freitas, T.M., Salciarini, D. 2022. The influence of initial shaft resistance mobilisation in the response of seasonally, thermally-activated pile foundations in granular media. Geomechanics for Energy and the Environment 32, 100299. Bowers, G.A. 2016. Ground-Source Bridge Deck Deicing and Integrated Shallow Geothermal Energy Harvesting Systems. PhD Thesis, Virginia Polytechnic Institute and State University, Blacksburg, VA. Brandl, H. 2006. Energy foundations and other thermo-active ground structures. Géotechnique 56(2), 81-122.