8The mechanical behaviour of the soil-structure interface plays a major role in the shear 9 characteristics and bearing capacity of foundations. In thermo-active structures, due to 10 non-isothermal conditions, the interface behaviour becomes more complex. The objective 11 of this study is to investigate the effects of temperature variations on the mechanical 12 behaviour of soils and soil-structure interface. Constant normal load (CNL) and constant 13 normal stiffness (CNS) tests were performed on soil and soil-structure interface in a direct 14 shear device at temperatures of 5, 22 and 60 o C. Fontainebleau sand and kaolin clay were 15 used as proxies for sandy and clayey soils. The sandy soil was prepared in a dense state, 16 and the clayey soil was prepared in a normally consolidated state. The results showed 17 that the applied thermal variations have a negligible effect on the shear strength of the 18 sand and sand-structure interface under CNL and CNS conditions, and the soil and soil-19 structure interface behaviour could be considered thermally independent. In clay samples 20 the temperature increase, increased the cohesion and consequently the shear strength, 21 due to thermal contraction during heating. The temperature rise had less impact on the 22 shear strength in the case of the clay-structure interface than in the clay samples. The 23 adhesion of the clay-structure interface, is less than the cohesion of the clay samples. 24 Résumé 27 Le comportement mécanique de l'interface sol-structure est d'une grande importance en 28 1 raison du rôle de l'interface dans la résistance due au frottement et la capacité por-29 tante des structures. Dans les structures thermo-actives du fait de la variation de la 30 température, le comportement de l'interface devient plus complexe. L'objectif de ce tra-31 vail est d'étudier l'effet des variations de température sur le comportement mécanique 32 de l'interface sol-structure. Des essais avec des conditions de charge normale constante 33 (CNL) et de rigidité normale constante (CNS) ontété réalisées dans une boîte de cisaille-34 ment directà différentes températures, 5 o , 22 o et 60 o C sur deséprouvettes sol-sol et 35 sol-structure. Le sable de Fontainebleau et le kaolin ontété utilisés comme materiaux de 36 référence pour les sols sableux et argileux. Les résultats ont montré que les variations ther-37 miques appliquées ont un effet négligeable sur la résistance au cisaillement des interfaces 38 sable-sable et sable-structure dans les conditions CNL et CNS et que le comportement 39 du sable peutêtre considéré commeétant indépendent de la température. Dans l'argile 40é tudiée, l'augmentation de la température augmente la résistance au cisaillement en rai-41 son de la contraction thermique pendant le chauffage, ce qui augmente la cohésion du 42 sol. L'augmentation de température a eu moins d'impact sur la résistance au cisaillement 43 dans le cas de l'interface argile-structure que dans leséchantillons argile. L'adhésion de 44 l'interface argile-structure est infér...

The mechanical behaviour of the soil-structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermo-active structures, due to non-isothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and soil-structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on soil and soil-structure interface in a direct shear device at temperatures of 5, 22 and 60 °C. Kaolin clay was used as proxy for clayey soils. The results showed that, in clay samples the temperature increase, increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay-structure interface than in the clay samples. The adhesion of the clay-structure interface, is less than the cohesion of the clay samples.