Barrette piles are rectangular piles which allow the foundation to bear axial and high moments. It is ideal for grounds structured upon boulders and alluvial soil. Hence, it is adaptive to any geological conditions. Similarly, the same type of machinery and equipment is utilized as it is used in the diaphragm and cut-off walls. Pile caps can be disgarded if barrettes and large diameter bored piles are used and the piles can be extended upwards without change of shape to form the single pile barrette-column system.
It is a type of drilled and cast-in-place pile but the thing which makes it different is its character with the shape and the style of the drilling. The tools which are used during the process are grab-bucket or hydrofraise type tools. The size of the piles will determine the size of the tools. The piles are constructed with a stantart size grab-bucket the size of which are ;
- width : 0.52, 0.62, 0.82, 1.02, 1.22, 1.52 m
- length : 1.80, 2.20, 2.70, 3.0 m
Based on these dimensions bigger and more rigid piles such as H-shaped piles, T-shaped piles can be constructed. The technical calculations are performed through similar methods with drilled and cast-in-place circular piles.
The phases of the operation carried during the construction process is consisting of 3 stages;
- drilling,
- putting the reinforcements in place,
- concreting.
Just like it is done with the classical diaphragm wall, the drilling is commenced utilizing bentonite slurry. The the operation plaform is poor the guide walls can be used for the same purpose.
Once the drilling slurry is desanded the reinforcement cafe is lowered into the opening. Utilizing a tremie pipe, the concrete is casted. Multiple pipes can be utilized in accordance with the size of the pile. After desanding the drilling slurry, the reinforcement cage is lowered into the trench.
Concreting is done in the usual way with a tremie pipe. Depending on the size of the pile, several pipes may have to be used.
What makes the barette pile advantageous is that its shape which allows mobility in several conditions :
resistance to horizontal stress and to bending moments better than circular piles of the same section,
easy adjustment to structures, so that one single pile is sufficient under each column or bearing unit,
better mobilisation of lateral friction than a circular pile of the same section, because of a larger perimeter.
The preferred application site is where high bearing capacities are required from 5000 kN and upwards.
As it allows to extend the area, it is a limitless foundation utility.
Commencing the works, quality shall be assured with below guidelines strictly;
- the quality of the slurry, the verticality and the depth of the borehole,
- the position of the reinforcements,
- the volume of concrete at each level.
After the concrete has set, a quality control inspection shall be carried out utilizing sonic control systems. 4 or more pipes shall be inserted into the pile to achieve this . Up to know, we have gained exact results utilizing the sequence of this quality control technique.