The mechanical behaviour of soils under non-isothermal conditions is a crucial factor in the analysis and design of energy geostructures. To investigate this behaviour, thermal direct shear tests were conducted in this study within the practical operational temperature range (8-45°C) of energy geostructures. Normal stress was applied in the range of 100 and 400 kPa. Within the scope of the study, continuous heating and cooling was adopted as thermal loading protocol and therefore, the effect of creep was not examined. Furthermore, the impact of soil type on the temperature-dependent shear strength parameters of soils was investigated. Results show that hardening behaviour was observed for normally consolidated (NC) clays while there was no change in the behaviour of sand. There was an increase in apparent cohesion for both heating and cooling episodes. Angle of friction remained unchanged for sand during tests while in NC clays lower friction angle is observed at higher temperatures. Obtained experimental results are reported and used to discuss the practical implication of the dependency of soil strength parameters on temperature in design and performance of energy geostructures.@en