Barrette Piles in Foundation System of Petronas Twin Tower

Petronas Twin Tower is a 452 m high skyscraper located in Kuala Lumpur Malaysia. These great structures (twin towers) were tallest building of world until Taipei 101 was built. The regime of this structure was between (1998-2004). We have published posts about architectural feature, structural and also damping facilities of these towers. We also published about testimonial of Taipei 101 under earthquake, its construction constraints and also tuned mass damper of Taipei 101. Of these posts, tuned mass damper becomes popular. You are all invited to visit all posts.
As foundation system is concerned, we will first discuss about the foundation system and then we will go to the piling types. Geotechnical investigation explored that the actual construction of these mega structures was on soft rock and decayed limestone. Both occupied almost equal portions of construction site. Then engineers were decided to relocate the structure to be sat it on entirely soft rock and moved it to around 61 meter to achieve this. 104 nos piles of an average 125 m piles were used to reach deep bed rock which made it having deepest foundation system of the world.
Reinforcement placing for Raft foundation construction in PETRONAS TowerThe single stage largest and longest concrete pouring of the history of Malaysia was conducted to embed this huge number of piles to form a raft from which a retaining wall of 21 meter was raised along a perimeter of more than 1000 meter. The raft had a giant thickness of 4.6 meters having weight of 32500 tonnes. This record was hold unbroken till 2007 in respect of largest pour. The raft comprised 13200 cum of concrete which required 54 hours to pour for each tower.
Skybridge of Petronas Towers
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.
Pile head breaking is on progress of a massive barrette pile
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. 

Besides Petronas twin tower, Capital Tower, Sail @ Marine Bay, interchanges of Farrer road and Adam road, new SGX center and railway station at Serangoon etc. are the example of application of barrette piles.

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