ABSTRACT
The growing energy needs of urban areas and the environmental context are leading to the development of new geothermal technologies. In this context, energy geostructures, such as thermo-active (or energy) piles, were developed in the early 1980s and consist of heat exchanger tubes fixed to the reinforcement cages of foundation piles to extract/inject heat from/into the ground to meet the heating and cooling needs of buildings. Their specificity lies in their dual function: structural support and energy exchanger. Therefore, two aspects can be critical and should be considered in their design. The first is the nature of the cyclic thermal load acting along the energy pile, which can affect its mechanical response. Consequently, the cyclic thermal loading can cause a variation in the shear stresses at the soil-pile interface, thereby affecting the pile’s load-bearing capacity. The second aspect concerns the adaptation of the design under combined lateral and axial loading, i.e. the interaction between lateral (or axial) loading and the axial (or lateral) behaviour of the energy piles, coupled with volumetric thermal loading acting on the surrounding soil and along the pile. These configurations are the most favourable for the installation of heat exchange tubes, as they mechanically require reinforcement cages along the entire lenght of the pile. The objective of the COOP project, funded by the French National Research Agency (ANR), is to improve the knowledge of the behaviour of energy piles under these complex load configurations by proposing different research topics, from real experimental case studies to physical centrifuge modelling and numerical modelling, with the final aim of providing engineers with a relevant tool for the design of energy piles under combined loading.
