Injection of a Microfine Cement Grout for the Tunneling of Meteor

The fourteenth line of the Paris metro (France), called Météor, is currently extended towards Saint-Lazare railway station in a very busy and historic district of Paris. The Transport Company (RATP), as a contracting authority, is then confronted with a complex environment. The constraints have determined works planning and construction methods. In particular, the alluvial deposits were reinforced by injection of microfine cement grout whose fluidity allows to accurately permeate fine soils. It was preferred to more traditional and potentially polluting grouts. After a description of the geotechnical conditions of the site, the different steps of underground constructions are briefly showed. Many control measurements have been integrated to the project to ensure the integrity of the surrounding structures. Grout pressure was thus continually fitted to the heaving of the foundations of sensitive buildings. In situ pressuremeter tests were also carried out before and after grout injection in order to verify the quality of soil improvement. Likewise, triaxial tests were performed on uncemented alluvial deposits and on alluvial deposits grouted in the laboratory. These tests show that the mechanical properties of the alluvial deposits were clearly improved by grouting