Experimentation of the Thermo-Mechanical Behavior of the Soil-Concrete Interface

The thermo-mechanical behavior of soils has been the topic of many studies over the last few decades and nowadays is closely related to the promotion of Energy Geostructures (EGs), aimed at reducing energy consumption from fossil fuels and the consequent emissions. During their operation, EGs are subjected to thermal variations due to the exploitation of the low-enthalpy geothermal resource, and this can have an impact on the structure response. To contribute in having a more precise framework of the complex mechanisms that affect the thermo-mechanical behavior of the EGs–soil interface, a modified testing device has been developed at the Laboratory of Geotechnical Engineering of the University of Perugia. A conventional direct shear apparatus has been equipped with a heating plate at the base of the soil samples, where a temperature probe for continuous temperature control has been integrated. In this work, the first results of an experimental campaign conducted to determine the influence of temperature on the shear behavior of soil and soil-concrete interface are shown. Temperature-controlled, direct shear interface tests were carried out at normal stress values ranging from 25 to 100 kPa. By comparing the results obtained for heated and not-heated interfaces (constant thermal load of 30 ℃ vs. room temperature of 20 ℃), a limited effect of the temperature variation on the interface shear strength was observed, with a slight increase of the interface friction angle with heating.