In order to evaluate the effect of energy piles' geothermal activation on the soil-pile interface behavior, at laboratory scale, a series of direct shear tests were performed using a device adapted for cyclic thermomechanical loading. A series of interface direct shear tests were carried out for three different thermal loading scenarios, i.e., at a constant temperature of 13°C, and for two different cooling-heating (8-18°C) cycles. The volumetric deformation after 10 thermal cycles was evaluated, and the shear test results were compared.

The energy walls or thermally active retaining walls are the dual-purpose structural component that operates in the shallow depths of the ground. For the efficient thermal design of these structures, simple analytical solutions are required to characterize their heat transfer. In this extended abstract, we compare the temperature change computed across energy walls for different calculation methods, including steady-state shape factors and numerical approaches drawing an analogy between the buried pipes used for district heating pipelines.

1. A new direct shear setup to measure the non-isothermal shear strength of the partially saturated soils and the soil-structure interface is developed. 2. The apparent interface friction angle is not significantly affected by matric suction at varying temperatures, but a slight decrease has been observed upon heating at all matric suctions. 3. Apparent adhesion increases with temperature increase/decrease, with a decreasing rate as suction increases, while the interface desaturation leads to higher apparent adhesion at all temperatures, corresponding to peak and residual values.

Dear reviewers Thank you for your constructive comments. In the revised version, “sponge material” has been replaced by “insulating foam”, “dense D” by “dense (D)”, and "Considering that...phenomenon." by "Considering that...phenomenon," following the suggestion of the reviewer. Another figure has been added to show the developed geothermal shear box.