Abstract:Based on Qinghai—Tibet Railway engineering,considering construction heat disturbance and global climate warming,aiming at the problem of pile foundation stability in high temperature permafrost regions with permafrost table descending,numerical simulation research and physical simulation tests have been carried out. The bearing capacity characteristics of land bridge are studied under the condition of permafrost table descending. Vertical bearing capacity of single pile as well as the influence rules of pile foundation with permafrost table descending are obtained. Ultimate bearing capacity of pile foundation reduces sharply with the permafrost table descending;and the side resistance of the pile foundation has the similar regulation with the permafrost table descending,which becomes smaller in the vertical bearing capacity of single pile. Simultaneity,bottom resistance takes on more and more important effect. The bad aftermath of the permafrost table descending can be illuminated by both numerical simulation research and physical simulation tests. So,the protection of frozen soil around the pile foundation needs to be strengthened,which can avoid frozen soil to degenerate,especially in the soundly sensitive high temperature permafrost regions. Reference basis is provided for the stability of land bridge along Qinghai—Tibet Railway and the design and construction of pile foundation in high temperature permafrost regions.