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Over the past twenty years, a substantial amount of research has been performed to expand the modeling capabilities of energy geostructures: innovative earth-contact structures that provide combined structural support and renewable energy supply. Several analytical and semi-analytical solutions have been made available for describing the thermo-mechanical behavior of cylindrical energy geostructures such as energy piles. However, no analytical solutions for capturing the thermo-mechanical behavior of plane energy geostructures such as energy walls and slabs have been developed until recently. This paper summarizes the essential features of the first analytical solution available for describing the thermo-mechanical behavior of plane energy geostructures. This analytical solution extends Winkler’s model for a beam resting on an elastic soil mass to non-isothermal conditions, allowing to quantify the effects of temperature variations, axial loads, transversal loads and bending moments applied to plane energy geostructures. Such an analytical solution can be used in the analysis of an elementary unit represented by a single beam as well as complex plane energy geostructures using the superposition principle. Based on the preceding capabilities, the proposed analytical solution may effectively serve the analysis or design of plane energy geostructures under the influence of mechanical and/or thermal loads.

The subsurface represents space and resource of ever-growing importance to meet human activity needs associated with the availability of built environments and energy. So-called energy geostructures represent a breakthrough technology in this context. By integrating the structural support role of earth-contact structures with the heating-cooling role of shallow geothermal heat exchangers, energy geostructures can sustain or enclose built environments while providing them with renewable thermal energy. Despite such promising features, the integrated roles of energy geostructures pose various challenges to understand their behavior and performance, and to address the related analysis and design. Appropriate formulation and application of scientific theory are crucial for the successful analysis and design of energy geostructures. This Bright Spark Lecture Paper presents selected theory for addressing the behavior and performance of energy geostructures, and discusses the application of this theory to analysis and design. In this context, the work focuses on energy piles and barrettes, energy tunnels, as well as energy walls and slabs. The ultimate goal of this paper is to provide competence for facilitating future research and development of energy geostructures across science and engineering.

To date, the majority of the available studies on the volume change behavior of soils under non- isothermal conditions have focused on fine-grained soils. Only a limited number of investigations have been made available about coarse-grained soils despite their abundance in practice, with contradictory features. To enrich the current knowledge about the volume change behavior of coarse-grained soils under non-isothermal conditions, this investigation presents the results of oedometric tests with temperature control performed on saturated sand. The influence of relative density on the volume change behavior of the tested material under non-isothermal conditions is investigated under a minimal level of applied vertical effective stress. The results show an expansive volume change upon heating and contractive volume change upon cooling for all relative densities. The magnitude of the contraction is more significant than that of the expansion, leading to a residual contractive volume change after one cycle of heating and cooling. The results of this study enrich the current literature about the volume change behavior of coarse-grained soils under non-isothermal conditions. Such competence may be considered for applications at the interface of geomechanics and energy wherein temperature variations occur and characterize the response of coarse-grained soils.

The application of a direct current electric field to porous materials such as soils in the form of an electrokinetic treatment induces a variety of multiphysical phenomena. Critical phenomena involved during an electrokinetic treatment of soils are electrical migration (i.e., movement of ions), electroosmosis (i.e., movement of water), electrolysis (i.e., breakdown of chemical compounds), and electrochemical reactions (i.e., oxidation/reduction and precipitation/mineralization reactions). Such phenomena lead to changes in the structure of soils. As changes in the structure of soils induce variations in their properties and behaviors (e.g., thermo-hydro-mechanical), electrokinetic treatments represent resourceful means to address broad geoengineering challenges. The purpose of this paper is to highlight the potential of electrokinetic treatments as versatile techniques capable of providing solutions for diverse geoengineering applications via a controllable change of the properties and behaviors of soils. From this perspective, this work specifically encompasses electrokinetically induced phenomena in soils and expands on opportunities in the context of geoenergy applications, among others, which can be mediated by electrokinetic treatments.