Abstract:
E4 The Stockholm Bypass – is a new route for the European highway (E4) past the Swedish capital Stockholm. The Bypass will connect the southern and northern parts of Stockholm. It will be one of the longest road tunnels (18 km) in the world. The Bypass is with that the largest rock fissure grouting operation undertaken for road tunnels (total 55 km) in Sweden. Due to a more hydraulically conductive rock mass than expected a significant risk of exceeding the allowable water ingress (Environmental Court decision) was imminent. To counteract the negative trend an improved grouting design had to be developed. The new grouting design is based on an extensive follow-up of previous grouting works, including rock characterization, hydraulic rock mass properties, grout take, grout mixtures, grouting pressures, grouting classes, Measurement While Drilling-data, water ingress measurements etc. The observational method, as it was intended to be used, is implemented in the new design in a way that has never been done before in Sweden. The observations during grouting are expressed as acceptance criteria with attached check points to verify that the proper grouting class (GC) is chosen or to decide on how to continue or stop grouting. Based on the outcome of each acceptance criterion, either a different GC is chosen (up or down) or an additional grouting round is ordered in the actual GC, or the grouting is stopped already after the first grouting round. A grouting fan will be considered complete only when the acceptance criteria (check points) according to a flow chart belonging to each GC is fulfilled. For the choice of effective grouting pressures and stop criteria such as grouting time the theories (analytical solutions) constituting the Swedish Real Time Grouting Control method (RTGC) are used. RTGC is based on around 40 years of extensive grouting research. Keywords: Pre-excavation fissure grouting, cementitious grouts, Observational method, Grouting classes.