A novel theoretical model to predict thawing settlement of clayey permafrost

Abstract

As infrastructure construction increases in cold climates, the thermal deformation of frozen soil needs to be taken seriously. In contrast to frost heave, thawing settlement is another type of thermal deformation less attention received in recent years but has yet caused significant harm to early infrastructure like roadways, railways, and pipelines in cold climates. Engineers attempted to foresee the thawing settlement of frozen soil before design, but there was no universally accepted and satisfactory theoretical model for the prediction. Based on the four-phase charting of frozen soil and taking into account the change of frozen soil systems experiencing thawing settlement, an original theoretical model is developed. The derivation offers seven postulates, induces three new factors that describe the thermal-hydraulic- structural characteristics of soil, and attempts to take specimen scale into account. The innovative model adopts initial water content and dry density to forecast the thawing settlement coefficient. Thawing settlement data of clayey permafrost from various regions of Northeast China were substituted for verification. The model demonstrates that in addition to the initial water content and dry density, the unfrozen water content, water holding capacity, and skeletal structure maintenance properties of frozen soil also affect the thawing settlement of frozen clayey permafrost but with different weights. The model also explains some essence of thawing settlement distribution problems. Finally, a happening probability list of various thawing settlement coefficients is provided based on the probability of various combinations of water-holding capacity and skeleton structure.