The Chambon Dam is a gravity dam type structure, made of Cyclopean concrete without reinforcements (except crowning and sidewalks), built between 1930 and 1935. It is 90ml high for a total length, at the 293ml crown level.
The upstream facing is vertical and shows a 5% inwards inclination in the current zone. The downstream facing is vertical on the upper 5 ml and then slopes to present an inwards inclination of 70% to 75%. The slope straightens to 23% in the lower part.
Affected by an alkali-reaction pathology, the Chambon structure is subject to a high rate of concrete swelling (maximum deformations around 50 μm / m / year observed in the vertical direction).
This phenomenon is at the origin of the main disorders identified on the structure such as longitudinal cracking of the upper part of the dam and degradation of the downstream facing.
The work to be carried out relates to the structural reinforcement of the dam following the swelling and cracking of the concrete.
The target is to preserve the monolithism of the structure thus avoiding projection of blocks in the event of an earthquake. The principle of con-strongly is based on the installation of pre-stressed upstream / downstream tie rods supplemented at the upstream level by the installation of a “net” made up of a mesh of carbon strips, intended to retain in case of earthquake of smaller elements not directly retained by the tie rods
The distribution of the seismic surface stress between the diagonal, horizontal and vertical carbon-fibre strips is as per follows: the areas between the strips have a triangle shape and the cutting follows their barycentre.
The loading in each section is therefore not uniform but triangular. Each strip deforms under the pressure of a wall section. Each strip has been modelled with the use of the in-house developed Pythagore software as a non-rigid cable, divided in 18 smaller 20cm-long cable elements. The deformations under seismic forces or seismic plus concrete heave forces have been analysed.
setec tpi carried out all of the project execution studies, including :
- The sizing of the 1,382 carbon bands
- Calculation of 411 stainless steel anchoring devices
- Calculation of 411 prestressed tie rods
- Production of all formwork and reinforcement plans
PM group: EDF / Tonello (Execution studies : setec tpi)
Construction Company: Bouygues TPRF
Duration: Déc. 2012 – Nov. 2013