Project Description

Context of the project

EDF operates the hydroelectric power station of Cusset, located in Villeurbanne (Rhône, France). The station was built around 1895. A bypass canal, called Canal de Jonage, 8km long, was built at the same time to supply the water turbines of the dam. But since 1995 EDF noticed the formation of a subsidence on the right embankment where the right bank joins the sluice gate of the dam.

Description of the project

In the next year, EDF forecasted a 5km long cut-off wall project for this 10m high embankment. But they decided to carry out a 160m long cutoff wall nearby the station as a matter of emergency.

The embankment is made of 10m sand and gravel backfill and pebbles, sometimes without matrix, and then natural compact gravels. EDF determined a socket of 2m in this compact soil layer and 5m nearby the station. The depth of the cut-off wall is between 12 and 15m.

Our solution

The technique Geomix® consists in mixing the soil, without excavation, with a cement slurry. The cement content of the slurry is adjusted to match a hydraulic conductivity criterion of 10-9m/s. The Geomix® process has been chosen to the detriment of injection treatment or slurry wall for the following three reasons:

  • Less spoil, reduction of environment impact (waste, traffic),
  • Quick setup of the wall (no repetitive grouting steps),
  • No fluid under pressure inside the embankment (risk of instability).

When obstacles (concrete, boulder, wood), first recognized or not, have been punctually prevented the Geomix® cutting head to drill deeper, an additional grout treatment has been implemented below the obstacle.

The combination of Geomix® and grouting allow to reduce the impact of encountered obstacles to the bare minimum of resources, duration and costs.

Type of project:

Maritime and river structures


Subsidiary of Soletanche Bachy:

Project owner:

Prime contractor:

EDF – Centre d’Ingénierie hydraulique – Grenoble

Main contractor:

Soletanche Bachy France

Works period:

01/2011 – 02/2011

Types de techniques :

Soil Mixing

Cut-off wall

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Key figures of the project

of Geomix® cut-off wall
bores 18 m deep for soil investigation drilling
water standpipes and groundwater table monitoring installed

Relative techniques

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