Abstract:
The West Link is an eight-kilometer double track railway through the city center of Gothenburg, Sweden’ s second largest city, in the south-west part of the country. The total cost for the project is estimated to around 20 billion SEK (around US$ 2, 3 billon), the construction works started in 2018 and the estimated opening is in 2026. The project includes three new underground stations and around six kilometers of tunnels in alternating rock and soil. The rock generally consists of crystalline rock while the soil is mainly soft clays with thin layers of non-cohesive soils and till at the bottom. The conditions are complex and include surrounding buildings sensitive to groundwater draw-down, existing tunnels that already impact the groundwater conditions, a sparse groundwater recharge, and complex geology. Which led to the very strict environmental requirements on permitted water leakage into the tunnels: large parts of the rock constructions have restrictions down to around 2-4 L/(min, 100 m tunnel). In addition, the stations and tunnels have complex geometries, sometimes a small rock-cover and short distances to existing tunnels. In order to meet the demanding requirements and conditions, the design of the grouting for the West Link project was based on the research carried out in Sweden over the last decades together with experiences from other major projects. The article describes the grouting design, the main challenges connected to execution, the evaluation of the grouting works so far, and how the environmental requirements are met. Examples of demanding hallenges are sealing of the large caverns for the railway stations, grouting of partially clay-filled fractures, and difficulties to seal rock with a sparse and sometimes not well-connected fracture system. Keywords: Grouting in hard rock, Tunnelling, Underground constructions, Crystalline rock.