Impacts of Permafrost Mean Annual Ground Temperature and Ice Content on Thermal Regime of Pile Foundation of Qinghai-Tibet Power Transmission Line

Abstract

The ±400 kV Qinghai-Tibet Power Transmission Line (QTPTL) was officially operated in December of 2011 on the Qinghai-Tibet Plateau (QTP) in China, crossing 550-km-long permafrost and 438-km-long seasonally frozen ground regions. Some of tower foundations of the QTPTL were buried in permafrost. It faces potential challenges of freeze- and thaw-related geohazards induced by freeze-thaw cycle, active layer thickening and permafrost degradation, which are mainly caused by climate warming, surface disturbance, enhanced heat transfer of concrete pile. These geohazards has become the concerns for stability and integrity of the QTPTL. In this study, some numerical tests on the thermal interaction between pile and permafrost were carried out to investigate impacts of permafrost mean annual ground temperature (MAGT) and ice content of soils surrounding pile on active layer thickening, permafrost degradation and freeze-thaw cycle considering climate warming, surface disturbance and enhanced heat transfer of concrete pile. The research results and discussions are described, which will provide the basis for normal operation and option of countermeasures against thaw settlement and frost jacking of the QTPTL, and the reference for the similar permafrost engineering in cold regions