A barrette is a cast-in-place reinforced concrete column. A barrette may also be defined as a rectangular diaphragm wall element that is being used as deep foundation. The construction includes the excavation of a trench under the protection of a support fluid (i.e. a thixotropic slurry such as bentonite mud for example).
Installation process in accordance with the requirements of NBN EN1538:2008
1. In advance construction of temporary guide walls and filling of the guiding trench with the thixotropic stabilizing fluid
2. Excavation through the supporting fluid suspension by means of a soil cutting grasp (clam shell grab) or hydrofraise, up to the required installation depth.
In order to avoid instability of the trench, the level of the bentonite slurry in the excavation trench should at any moment be maintained at least 2 m above the highest water level in the full height trench, especially in the case of an artesian aquifer.
3. Desanding or replacement of the bentonite suspension, placement of the reinforcing cage and concreting with one of more tremie pipes, depending on the size of the barrette
4. As concreting progresses the concreting tube(s) is (are) pulled up gradually, during which the bottom is always be kept sufficiently deep in the already poured concrete, to avoid each interruption in the continuous concrete flow.
5. Completed barrette