Large-Scale Post-Grouting Works in the Stockholm Bypass-PPT Presentation

PPT Presentation

Pdf Summary

The Stockholm Bypass is a 21 km road tunnel forming part of a 60 km tunnel network, with three lanes in each direction. Construction began in 2016, and opening is planned for 2030. The project’s leakage target is approximately 3–4 litres per minute per 100 metres.<br /><br />Despite pre-grouting and other water-control measures, some sections required extensive post-grouting. The work was costly and constrained simultaneous tunnel progress. In one rock-work contract, additional post-grouting costs exceeded €200 million against an initial total budget of €500 million.<br /><br />The project used a systematic approach to identify and treat problem areas. Leakage measurements, tunnel-face observations, geological surveys and measurement-while-drilling data helped locate areas for treatment. Grouting was carried out in overlapping fans using split spacing, with follow-up records tracking grout consumption, pressure, grout properties, connections between holes and leakage. The grout mix and procedure could be adjusted as work progressed.<br /><br />Treatment needs varied considerably: some areas were successfully grouted in one or two rounds, while others required extensive work. Roof-and-wall grouting was relatively quick, reduced dripping and generally used less grout. Bottom grouting reduced inflow more effectively but typically required greater grout volumes, time-consuming cleaning and restricted access for other tunnel activities. In some sections, two to three rounds were performed in the bottom.<br /><br />The presentation highlights the importance of measuring and documenting leakage consistently, targeting treatment based on site conditions, and evaluating results after each grouting round. Factors associated with extensive post-grouting included topography, soft rock, low rock cover, convergence and tunnel size.

Keywords

Stockholm Bypass

road tunnel

post-grouting

water leakage

tunnel construction

grouting measures

leakage monitoring

rock geology

bottom grouting

tunnel excavation