Permafrost research in China related to express highway construction

Express highways are roads of high speed, large capacity, and transportation flexibility. The network of express highways in China has been developed over the last 30 years to accommodate the needs of a growing population and to facilitate economic development. Part of the network is in permafrost regions, where the construction and maintenance of these roads present significant engineering challenges due to permafrost degradation induced by climate warming and by construction. This paper summarizes the engineering problems encountered in the construction and maintenance of these express highways, and the mitigation techniques used to overcome them on new transportation projects in permafrost regions. Ten types of engineering problems along the Qinghai‐Tibet Highway, the oldest and longest highway in the permafrost regions of China are identified. Their main cause is related to permafrost degradation in the subgrade beneath the road subbase. Settlement of the highway embankment due to thaw consolidation of degrading permafrost is the dominant mechanical distress observed. Mitigation techniques, mainly for enhancing heat convection beneath express highways, are discussed along with their effects. Research in China related to transportation projects may provide a reference for future express highway design and construction in permafrost regions around the world.