Investigation of thermal effects on the saturated shear behaviour of a clayey sand-structure interface

The mechanical behaviour of soil-structure interfaces at various temperatures plays a key role in predicting the performance of energy piles, such as their ultimate bearing capacity and settlement under heating and cooling. The experimental data was limited in the literature, and previous studies used clay and clean sand. In this study, a modified direct shear apparatus that can control temperature was developed. To control interface temperature, a refrigerated/heated circulating bath is connected to channels in the lower shear box and then heated/cooled water is circulated. The interface can be heated/cooled through heat exchange with circulating water. Three series of tests were conducted at various temperatures of 8, 20 and 42 °C and effective normal stress levels of 50, 150 and 300 kPa. The soil specimen was recompacted clayey sand with a 95% degree of compaction. The results indicate that the shear strength of saturated soil-structure interfaces decreases with increasing temperature. This is likely because temperature elevation results in a reduction of interface roughness and a partial increment of void ratio in the shear zone.