Geotechnics Towards Sustainability

Our contribution stemmed from two topics: first, the incorporation of unsaturated soil mechanics into the geotechnical design of retaining structures and second, the development of shallow geothermal technologies that satisfy the thermal requirements of the built environment. Both projects were a product of a close collaboration with Nobatek/INEF4 (France).

Analytical and experimental analyses were performed to investigate the interaction between unsaturated soils and retaining structures. In particular, the work highlighted the effects induced by negative pore water pressure on the lateral earth thrust. In the context of geotechnical design optimization, the obtained results encourage the adoption of unsaturated soil mechanics and contribute to fill the gap between research and practice.

Additionally, we worked on developing the use of underground infrastructures as shallow geothermal systems. By including heat exchangers secured to the geostructures and exchanging heat with the surrounding materials, underground railways, train stations, multi-floored basements, and tunnels can serve as thermo-active elements. Aspects linked to the thermal performance were also investigated. Our primary contribution was the proposition of a thermal performance design methodology that enables engineers to quantify the thermal potential of underground energy infrastructures. Our work also analysed the environmental performance of energy pile foundations through the implementation of a Life Cycle Assessment model. Such model highlights the efficiency of this technology when compared to conventional systems: noteworthy environmental savings were found for both heating and cooling.

Within the TERRE project, in 2017 we hosted the “International Doctoral School on Unsaturated Soil Mechanics” at EPFL with over 60 international participants including world renowned experts in the field.

The published scientific outputs are available Open Access in international scientific journals, as listed below. Our involvement in the TERRE project helps advance geotechnical engineering towards a low-carbon future.

Main outcomes

• PhD thesis: Speranza, G., (2020). Geotechnical and environmental performance of retaining structures in unsaturated soils.
• PhD thesis: Zannin, J. (2020). Thermomechanical behavior of underground energy infrastructures.

List of publications

• Zannin, J., Ferrari, A., Pousse, M., & Laloui, L. (2020). Hydrothermal interactions in energy walls. Underground Space.
• Zannin, J., Ferrari, A., Larrey-Lassalle, P., & Laloui, L. (under review), Early-stage thermal performance design of thermo-active walls implemented in underground energy infrastructures. Geomechanics for Energy and the Environment.
• Sutman, M., Speranza, G., Ferrari, A., Larrey-Lassalle, P., & Laloui, L. (2020). Long-term performance and life cycle assessment of energy piles in three different climatic conditions. Renewable Energy.
• Speranza, G., Ferrari, A., Larrey-Lassalle, P., (under review), Life cycle environmental assessment model of retaining structures in unsaturated soils. Geomechanics for Energy and the Environment.
• Speranza, G., Ferrari, A., Maxime, P., & Laloui, L. (2019, June). An experimental investigation on the water retention behaviour of a silty soil for the computation of the lateral earth thrust on a retaining wall. In 7th International Symposium on Deformation Characteristics of Geomaterials (IS-Glasgow 2019)
• Speranza, G., Ferrari, A., & Laloui, L. (accepted for publication). A physical model for the interaction between retaining structures and unsaturated soils. 4^th European Conference on Unsaturated Soils (E-UNSAT2020).
• Zannin, J., Ferrari, A., Pousse, M., & Laloui, L. (2019). Thermal design and full-scale thermal response test on Energy Walls. In 7th International Symposium on Deformation Characteristics of Geomaterials (IS-Glasgow 2019), E3S Web of Conferences (Vol. 92, p. 18011). EDP Sciences.

Involved people

• Mr. Gianluca Speranza, Mr. Jacopo Zannin
• Dr. A. Ferrari, Prof. L. Laloui