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H.G. Jodl, H. Toma:
"Evaluation of Tunnel Construction Methods";
Vortrag: International Symposium an Challenging Tunnel Construction, TU Wien; 02.05.2007 - 03.05.2007; in: "International Symposium an Challenging Tunnel Construction 2007-05-02/04 in Vienna, Austria", H.G. Jodl (Hrg.); Eigenverlag, (2007), S. 189 - 195.

Construction of a tunnel consists of many activities during the construction phase of the project. Supporting is one of these activities and responsible for the primary bearing capacity of the tunnel. Immediate support elements are provided to control ground movement caused by stress redistribution during tunnel drive. Certain support elements are assembled in the excavated areas of crown, bench, side wall and additionally on the tunnel face and/or invert if necessary. Typical support elements are rock bolts, reinforced sprayed concrete, girders, lances, etc. Loose ground and weak rock within the following rounds can also be supported using methods such as pipe umbrella, forepoling, earth wedge, etc. The Selection of efficient support methods for tunnelling is very important to reduce problems during construction and maintain project cost and time within the project budget and the planned schedule. This paper introduces a model that helps decision makers in selecting tunnel support methods in the conceptual phase of the project. The tunnelling activities such as basic tunnelling methods (e.g. NATM, cut and cover, etc.) and the details of tunnel construction (e.g. excavation, mucking, etc.) are the background of the model.

These activities and the factors controlling them are quantified. Expert opinion was used to determine the controlling factors. Efficiency degree, quantified by experts and efficiency percentages as other important components are defined. To obtain efficiency percentages the efficiency degree is combined with the user defined importance percentage of the controlling factor, expressing the importance of the controlling factors. The model calculates efficiency percentages of support methods based on project conditions. The model provides the user with a report including support methods and their efficiency percentages ranked in descending order. Most importantly, efficiency percentages are not only defined for individual methods bur for the combination of different methods. As a final result of this calculation process, the efficiency percentages of a particular tunnelling system (tunnel construction method) as a combination of basic tunnelling methods and activities are obtained. In a final report the alternative tunnel construction methods of a certain tunnel project are evaluated in a quantitative comparison in descending order.

Tunnel construction method, support methods, efficiency percentage