Adjustment of a grouting design during the production phase. Examples from the West Link-project

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Grouting design is preferably well-founded in adequate pre-investigations and analyses carried out during the design phase. Ideally an array of designs, presented in grouting classes, are prepared to achieve sufficient sealing for varying inflow requirements in various rock conditions. However, there will always remain uncertainties in any underground project, and these are typically handled by actively adapting the final design to suit the actual site conditions encountered during the production phase. The aim of this paper is to present the grouting design adjustments that were made during the initial production phase of the West Link-project (Västlänken), Sweden. The West Linkproject involves the construction of a double-track rail tunnel with three stations under the centre of Gothenburg. The project is divided into six major contracts and this paper focuses on results from the Korsvägen contract (E05). In the West Link-project, the client (Swedish Transport Administration, Trafikverket) has assigned contracts for adjustment of rock design during construction, including grouting. This paper describes the design pre-requisites that formed the basis for the initial grouting concept, as well as the method for collecting relevant information for evaluating the concept. The evaluation has been based on initial production experiences, increased geological knowledge and most important achieved tightness of the rock mass. Examples of adjustments of the concept involve the extent of grouting classes, performance and target value of control boreholes and more efficient use of stop criteria. In this paper, the background and implementation of the adjustments are presented, as well as their subsequent consequences for the production. Finally, technical and contractual factors that have influenced the design adjustments are discussed.

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