The Kanton of Zurich, Switzerland is constructing the Aeschertunnel as part of a highway improvement program. The project is composed of two parallel highway tunnels, each approximately 2 km long, with cross-sectional areas of approximately 135m2. The shallow tunnels pass through bedrock and glacial till. Tunnel construction commenced in the glacial till using a blade shield, which resulted in large surface settlements. The blade shield was replaced with sub-horizontal jet grouting from the tunnel face. The jet grouting technique reduced the surface settlements in the till to acceptable limits.; The jet-grouting installation and tunnel excavation sequence, including support installation, was carried out using the two-dimensional finite element software Phase2. The time-dependent material properties of jet grout were determined through laboratory testing and the staging in the model simulated the injection of a water-cement slurry that eventually hardened. The laboratory program focused on the short term (24 hr) development of strength and stiffness of a grout with a composition similar to the that used to construct the jet-grout columns. The numerical analysis showed that the jet-grouting sequencing had a significant effect on the shape of the settlement trough and the magnitude of the settlement. The results also showed that once the jet-grout columns were installed the tunnel support had only a minor impact on the ground deformations. (Abstract shortened by UMI.)
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