Disaster-causing mechanism and prevention methods of “pot cover effect”: Fid-Bau Portal

Disaster-causing mechanism and prevention methods of “pot cover effect”

Yao, Yangping / Li, Fuqiang / Lai, Yuanming

A large amount of water accumulated below the runway of Shenyang Taoxian International Airport caused frost heaving, which resulted in a wide range of cracks on the pavement. From the geological and environmental conditions of the engineering field, the possibility of capillary water migration and rainwater leakage is excluded. In the process of exploring this fraction of water, we put forward the concept of “pot cover effect.” The “pot cover effect” refers to the phenomenon that the water vapor in the overburden soil moves upward by temperature gradient and condenses into liquid water or decomposes into ice which accumulate under the overburden eventually. The existence of the phenomenon of “pot cover effect” was confirmed by laboratory experiments, and the phenomenon also recurred in the field experiments. The long-term impacts of the “pot cover effect” will inevitably lead to water accumulation in the shallow soil of the airport runway, and eventually induce pavement disasters. Contraposing to the mechanism of “pot cover effect,” we proposed the method of setting a separation layer in soil to block water vapor migration. Furthermore, the optimal depth of the separation layer was analyzed by numerical simulation of heat-water-mechanics coupling. The effective impacts of the separation layer on preventing “pot cover effect” are verified by field experiments. Eventually, the method of setting a separation layer was applied to the design of Beijing Daxing International Airport to prevent the disasters caused by “pot cover effect.”