Effect of a ventilated open structure on the stability of bored piles in permafrost regions of the Tibetan Plateau

摘要

Temperature is a key factor that affects the adfreeze strength between frozen soil and a structure. Under the influence of climate change, permafrost degradation reduces the bearing capacity of bored piles in permafrost regions. Based on the monitoring results of bored piles at a site in Beiluhe and related simulations, the effect of a ventilated open structure (VOS) on the temperature at the pile-soil interface and the bearing capacity of bored piles was discussed. The results showed that climate warming can significantly reduce the bearing capacity of bored piles. The higher thermal conductivity of concrete than frozen soil had a negligible influence on thermal stability of pile. However, the temperature at the pile-soil interface decrease drastically within a year due to the lower surface boundary temperature beneath a VOS. Numerical simulation indicated that the bearing capacity of bored piles with a VOS increases during the first 25 years and then decreased. While the bearing capacity without a VOS decreases over 50 years. A VOS can improve the stability of bored piles, delay bearing capacity degradation of bored piles for at least 50 years, and significantly reduce the design pile length.