Multiphase Modeling and Computational Simulation of Soil Freezing in the Context of Mechanized Tunneling

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The aim of this project is to develop a multiphase model for ground freezing that covers all essential aspects of ground freezing applied during shield supported tunnel excavation. This includes the coo-ling process by means of installed freeze pipes, the freezing process of the groundwater with the corresponding effects on soil deformations and the tunnel advance in frozen ground conditions including the multiple interactions between the shield driving process with the frozen ground. In the first project phase, a multiphase soil model has been developed within the theory of thermo-poromechanics, which allows the description of the coupled thermo-hydro-mechanical behavior of porous materials subjected to freezing, taking into account the phase transition between water and ice and the formation of ice lenses in a thermo-dynamically consistent form. In the proposed second project phase, the focus of research will be laid upon the modeling of the mechanical and rheological properties of frozen soil. The developed simulation model can be used as a forecasting and optimization tool for the design and execution of artificial ground freezing in tunneling. It will also allow a deeper understanding of the interacting processes between the shield driving and the support structure composed of frozen soil, and detailed studies of the influences of selected parameters.