Recently, a constitutive model has been developed to describe the mechanical behaviour of frozen soil as a function of temperature, all the way to the unfrozen state, and vice versa [1]. The model has been implemented as a user-defined soil model (UDSM) in the geotechnical finite element code PLAXIS 2D and applied in practical thermo-hydro-mechanical boundary value problems. One of the problems with the use of a model for frozen / unfrozen soil is that it involves several parameters of which quite a few are not very common to geotechnical engineers. Hence, one of the goals of this study is to provide more information on the meaning and the determination of the model parameters. As an example of the use of the constitutive model and its implementation, one application is presented: it is a chilled pipeline causing a drop in the ground temperature leading to frost heave. Its results show that the model can simulate frost heave in a qualitative manner, and that the robustness of the numerical implementation is still sensitive to the choice of boundary conditions, temperature gradients, and time.

1. Introduction

The replication of the behaviour of frozen soils has been studied for decades [2]. Many attempts have been undertaken to either develop new constitutive models or to improve already existing models to simulate the behaviour of frozen geomaterials. To handle the challenges of ground freezing, cold regions engineering and periglacial processes, it is vital to understand the mechanical behaviour of frozen soil. Knowing that field studies, large scale laboratory tests and centrifuge modelling offer a good insight, they are however expensive and time consuming. A numerical modelling approach is therefore necessary. The Norwegian University of Science and Technology (NTNU), in collaboration with Plaxis bv, developed a new numerical model [1] to tackle these problems. The aim of this new approach is to provide a reliable design tool to assess the impact of climate change and changes in temperature in general on a variety of engineering problems, in particular ground freezing for mine shaft construction.

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