New semi-analytical approach for ice lens heaving during artificial freezing of fine-grained material

Abstract

The calculation of frost heaving with ice lens formation is still not standard for construction projects using artificial ground freezing (AGF). In fine-grained material, ice lenses may initiate and lead to significant heaving at the ground surface, which should be considered in advance. However, the complex processes during ice lens formation are still not fully understood and difficult to capture in a simple approach. In the past, the semi-analytical approach of Konrad and Morgenstern used one soil constant, the “segregation potential (SP)”. It has been mainly and most successfully applied to the heave calculation of natural-induced soil freezing in cold regions. Its application to AGF has been so far unsuccessful. To solve this, a new semi-analytical approach is presented in this paper. It includes AGF conditions such as bottom-up freezing, temperature gradients to reach great freezing velocities, and a distinction between two freezing states. One is the freezing-up state until a certain frost body thickness is reached (thermal transient state), and the other is a holding phase where the frost body thickness is kept constant (thermal quasi-steady state). To test its ability, the results are applied to another freezing direction, the top-down freezing. The new approach is validated using two different frost-susceptible soils and, in total, 50 frost heave tests. In the thermal transient region, where the SP is applicable, the two semi-analytical approaches are compared, showing improved performance of the current method by about 15%.

Keywords

• Semi-analytical approach
• Ice lens formation
• Frost heaving
• Bottom freezing
• Segregation potential
• Frost-susceptible soil