Multiphase Flow in Unsaturated Soils and the Induced Deformation with Respect to Compressed Air Tunnelling

Shallow tunnels in the urban region are becoming more and more important. In certain ground conditions, the application of air pressure in the tunnel space in combination with the New Austrian Tunnelling Method (NATM) is employed to protect water inflow into the tunnel during construction. To capture the flow and deformation behaviours due to the compressed air tunnelling, interaction between fluid and mechanical processes in unsaturated soil must be concerned. The thesis presents a developed algorithm to simulate the three-dimensional compressed air tunnel advance in which the fluid-mechanical interaction is taken into account by means of loose coupling. The mechanical and fluid related properties of the studied sand are determined in the laboratory, e.g. in triaxial tests and permeability tests with compressed air. Characteristics of fluid related functions are determined by means of inverse modelling. Two examples show the ability to calculate heaving and settlements at the surface close to the tunnel face, which are measured in the field. Consequently the calculation method is a valuable tool during the design phase of future projects.