Axial loading behaviour of laboratory concrete piles subjected to permafrost degradation

Global warming causes a large area of permafrost degradation, which leads to increasingly engineering problems related to pile foundations in Tibetan Plateau, particularly in warm permafrost. The present research investigated the effects of permafrost degradation on the axial behaviour of concrete piles in warm permafrost. Quick axial compression tests were conducted on concrete piles installed in frozen soils in the cold room laboratory. Results showed that the behaviours of pile gradually degenerated with the increase of active layer thickness (z(a)) and ground temperature. The development of shaft resistance as the pile settled was compared at various cases. Adfreeze strength on the pile shaft was reduced with increased ground temperature. The adfreeze strength for concrete piles was obtained in silt and clay at temperature of -1.10 degrees C to -2.35 degrees C. Adfreeze strength was not reached near the pile tip. Piles in frozen soils could still gain the tip resistance at a displacement as much as 10% pile diameter and did not reach the plunging failure at such a displacement.