RER C - Saint-Bernard trench - Paris
Consolidating an existing structure with Jet grouting columns.
For many years, the vertical vault support and slab of France’s busiest railway line ("RER C" in its central underground section through Paris) have been damaged due to the structure’s poor foundation soil. Various past repair methods have not completely solved these problems. SNCF and its consultants decided to perform a general sub-structure review by treating the poor soil with Jet Grouting as far as infrastructure sub-faces. Thus, a four-week long, work-site wide, trial area was used while the line was cut off completely during the Parisians’ holiday season, in August 1996.
Jet grouting is a construction process that uses a high-pressure jet of fluid (generally 20 – 40 MPa) to break up and loosen the soil at depth in a borehole and to mix it with a self-hardening grout to form columns, panels and other structures in the ground. The parameters for the jet-grouting process and the desired final strength of the treated soil depend on a number of characteristics, such as the soil type, the technique used and the objective to be reached. In granular soils, the high-pressure jet breaks up the grains through erosion, while in a cohesive soil, such as clay, the jet breaks the mass up into small particles. High pressure is needed to produce the kinetic energy required for the jet through a small-diameter nozzle. Waste material from the process (a mix of soil, water and binder) is recovered at the surface before being taken away for disposal.
Soletanche Bachy has helped build most of the world's major metro systems, performing soil consolidation grouting and constructing cut-and-cover tunnels with cast-in-situ diaphragm sidewalls, bored tunnels and major underground openings.
Soletanche Bachy has developed a number of techniques for use in railway works; cut and cover tunnels, highways, underground stations, viaduct etc.
These works are carried out to reinforce foundations that have degraded with time or have been damaged by events. Where a structure is to be subjected to higher loads or forces than it was originally designed for, underpinning of the foundations is often required as part of its upgrade.
Voyage au coeur de l'ingénierie de pointe
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