Consolidation of thawing permafrost considering phase change

Abstract

When permafrost thaws, consolidation occurs under surcharge loads, leading to settlement which is one of the largest threats to infrastructures constructed in permafrost regions. This paper proposes a three dimensional thaw consolidation theory combining Biot’s consolidation theory with heat conductive equations considering ice-water phase change effects through specific heat. Numerical simulation was implemented. The theory was verified by comparing the degree of consolidation and pore pressure ratio calculated by this theory with that from closed form solutions for a simplified one dimensional problem. Thaw consolidation tests were carried out on frozen soil samples with four water contents and under two surcharge loads. Strains occurring in the tests were compared with those from the numerical calculations. It is found that with low water contents in the frozen soil, strain from thaw consolidation was relatively small, and was well simulated by the proposed theory. With increase in water content of frozen soils, the discrepancy between calculated and test results increases.