In shallow tunnelling below the groundwater table compressed air can be used for preventing water inflow into the tunnel. Using this method air loss takes place through both the unsupported tunnel face and shrinkage cracks of the shotcrete lining. Until today it is difficult to correctly estimate the amount of air loss during the design phase of a project, although this is a significant factor concerning the total costs of a tunnel. For solving the problem the multi-phase flow in the soil above the tunnel has to be considered. The aim of the conducted research project was to develop a numerical simulation of the air flow in the soil, based on existing unsaturated soil constitutive models. In the first stage large scale laboratory tests were conducted at the Institute for Soil Mechanics and Foundation Engineering in Graz to simulate the air-permeability of the shotcrete lining and the soil. Additionally, the experimental results were simulated numerically. In a second stage the numerical model was extended to a three dimensional simulation of tunnel advance under compressed air. In this contribution the results of the tunnel advance model with respect to the air flow into the soil through the cracked shotcrete lining and the tunnel face are presented and discussed.
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- Numerical simulation of air loss during tunnel advance in compressed air tunnelling
- Springer Berlin Heidelberg
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