Estimating Liquefaction Potential of Thawing Permafrost Soils, an Evaluation of Frozen and Recently Thawed Soils

摘要

Liquefaction, due to strong ground motions caused by earthquakes, is typically disregarded in permafrost soils. However, in cases where permafrost degrades, it can be challenging to estimate liquefaction potential using conventional screening methods. Historically, there have been several tools engineers have utilized to estimate the potential for liquefaction in thawing permafrost soils, such as those used for the Trans-Alaska Pipeline System (TAPS) in the 1970s. Recently more than one hundred boreholes were advanced in an area of discontinuous permafrost near Fairbanks, Alaska. The area is partially developed, which has resulted in decades of localized permafrost degradation. While the boreholes in the undeveloped area remained in a warm permafrost condition, others within close proximity showed thawed soils to depths greater than 50 feet. This study utilizes the close proximity of the frozen and thawed soils to evaluate historical liquefaction screening methods of frozen, thaw-susceptible soils and compares those methods to the results of current methods for screening of thawed soils for liquefaction. The findings from this study provide a methodology that can be further refined and used and identifies key issues to consider when evaluating liquefaction susceptibility at sites where climate change or development adversely affects permafrost soils.