Numerical Modeling of Air Losses in Compressed Air Tunneling

Abstract

A numerical model has been developed to predict the air losses from tunnel face and perimeter walls in compressed air tunneling. The model can also predict the zone of ground influenced by air flow from the face and walls of a lined and unlined tunnel. The model comprises a finite element analysis of the flow of air from the tunnel face and an analysis of the flow from the tunnel perimeter walls based on flow laws. The numerical model considers the stages in the construction sequence, geometry of the tunnel, soil layers, and time. Furthermore, the model accounts for the curing behavior of shotcrete, in particular, the time dependency of permeability. Field data from the Feldmoching Tunnel, U8 N‐8 in Munich, Germany, has been used as a case study to verify and calibrate the numerical model. The results of the analysis indicate that this model is suitable for predicting air losses in compressed air tunneling. Furthermore, the model predicts the areas of ground that are likely to be affected by the flow of air from the tunnel. This information can be used to assess the risk of settlement and other indirect consequences of the tunneling method.