Substantial degradation can occur to warm permafrost due to changes in surface conditions resulting from infrastructure development and climate warming. The associated geohazards, including differential settlement, slope instability, and liquefaction of degraded, unconsolidated materials in seismically active warm permafrost regions, pose substantial threats to the built infrastructure. Among them, seismic hazards of degraded permafrost have received little attention. This paper aims to provide a case study of an airport built on warm permafrost about 80 years ago, focusing on climate changes, permafrost degradation, and observed seismic hazards during a strong earthquake. The study site, that is, the Northway Airport, is located in a discontinuous permafrost area in Interior Alaska. Geotechnical data from 1973, 1991, and 2005 were compiled and analyzed to reveal permafrost degradation at various surface conditions, and are compared with the well-known degradation data from a site in Fairbanks. Furthermore, the responses of the airport runway during the 2002 Denali earthquake (Mw = 7.9), including liquefaction and lateral spreading displacements, are described and analyzed. And the seismic hazards of civilian airports built on permafrost across Alaska are surveyed. Distinct trends are revealed in two periods, namely, from 1943 to 1975 and from 1976 to 2021, for air temperature, precipitation, and wind speed. Permafrost tables were observed to drop with time at various rates for different surface conditions. Liquefaction and lateral spreading were observed extensively during the earthquake. The locations of observed liquefaction at the airport are mapped, and the lateral spreading displacements are estimated based on available photos. The standard penetration test data collected during geotechnical investigations are analyzed, and a liquefiable layer is identified at the talik between the active layer and the permafrost table. Moreover, 55% of Alaska's civilian airports are in permafrost areas. Among them, two-thirds fall within seismic zones with a risk level of 3 or above. This study demonstrates the high seismic risks of degraded permafrost and its potential impact on the built infrastructure.

Rising temperatures due to climate change can significantly impact the freeze-thaw condition of airport pavements in cold regions. This case study investigates the implications of warming temperatures on the freeze-thaw penetration and frost heave of pavements in critical airports across Canada. To this end, different methods were used in the quantification process through climate change simulations considering emission scenario RCP8.5 in 20 and 40 year time horizons. The results show that climate change would have different design implications for airport pavements, depending on their location. The predictions suggest a shallower frost penetration depth, and possibly less frost heave, for the airports not underlain by permafrost, while airports over permafrost areas might experience an increase in thickness of the active layer, ranging from 41 to 57 percent, by 2061. Among the different methods used in this study, it was observed that some methods performed better in predicting the frost depth of fine soils, while others worked better in the frost depth prediction of coarse soils. The results indicate the need for more mechanistic models to provide a more realistic prediction of freeze-thaw penetration, as compared to existing empirical models.

The thermal parameters of adherent layer are of great significance to the distribution characteristics of temperature field and foundation stability control of runway in permafrost region. This paper investigated the effects of annual range of temperature (A), annual average temperature (T-A), and other factors on the adherent layer thickness (H), temperature amplitude (A(0)), and annual average ground temperature (T-0), and further analyzed the thermal parameters of the adherent layer by using the FEM (Finite Element Model) roadbed temperature field and experimental data. The results indicate: A and average monthly total solar radiation (Q) have the most serious on H. A numerical method for determining the parameters of the adherent layer based on various conditions such as A and T-A was proposed by multiple regression. The temperature fields of the three types of pavements obtained by FEM and the experimental data were compared with the numerical calculation results for verification, and the conclusions were in close agreement, illustrating that the proposed method for calculating the parameters of the adherent layer is reasonable and effective. The research results extend the application region of adherent layer theory and provide a reference for runway construction in the permafrost region of Northeast China.

The permafrost in the Da Xing'anling Mountains Northeastern China has experienced rapid and significant degradation due to climate warming and human activities during the last few decades. In this study, the permafrost degradation and freezing/thawing characteristics of the active layer at Mo'he airport were investigated through a ground temperatures data set collected over 10 years of measurements. During the monitoring period, thawing permafrost under the airport was observed, induced by climate warming, and thermal disturbance of airport construction and operation. The permafrost table under the blast pad declined considerably and varied from - 9 m to -14 m, and from - 4.5 m to -12 m under the natural site. The maximum depth of frost penetration at this airport shows a decreasing trend. The freezing duration of soil under the blast pad is shorter comparing with the natural ground surface, while its thawing duration is longer. The warming rates of permafrost at -10 m depth under the blast pad were 0.25-0.33 degrees C/a, and those under the natural ground were 0.03 degrees C/a and 0.15 degrees C/ a. The results provide valuable data for designing, construction and operation of the airport, and a reference for other airports construction in permafrost regions.