Barrette Piles in Foundation System of Petronas Twin Tower : Part 2

Now we will learn about barrette piles. This pile is adopted in structures where high moments and horizontal forces in addition of usual vertical loads have to transferred to ground safely. These are rectangular piles that have a similar construction method of diaphragm wall construction.

As these section to be drilled is large, there boring with auger is avoided, rather an economical procedure is followed by excavating and protecting the sides. In regards to protecting sides, water based slurry like bentonite is used to stabilize and support trench walls while excavation is carried out.

After completion of excavation for barrette, steel cage as reinforcement is lowered and placed in central portion of excavation to be poured with concrete providing sufficient concrete cover around reinforcement. Concreting is done in continuous operation using tremie pipe extending to the bottom of the excavation trench. The procedures maintained are as used in regular pile concreting. We have published many posts regarding pile concreting. You can read those for better understanding.

The slurry provided to stabilize excavation is come out as concrete displaces it filling the volume in trench. The desanding process is used to treat this slurry and to be reused for surrounding barrette excavations. The usual size and depth used are of (0.8-1.2) m wide and 2.8 m length. But a depth of 150m can be achieved with these piles.

The largest foundation application example is Petronas twin towers. We have discussed earlier about foundation system of this mega structures. In Petronas tower, barrettes of 125 m were used that are subsequently embedded by huge raft slab. The massive foundation work was conducted by Bachy Soletanche and takes 12 month to complete.