Piling Contractors in Dubai

The rotary bored piling method refers to the installation of piles using drilling techniques.

Bored piles are drilled using buckets and/or augers inside a temporary casing driven in place by means of vibratory hammers or through twisting in place using the drilling rig itself. The temporary casing maintains the upper soil layers stable especially in water bearing stratum. Depending on the designed toe level of the pile, drilling underneath the casing may take place in stable soils such as soft rock or cohesive soils.

In unstable soil strata beneath the toe level of the top casing, the use of bentonite fluid or polymer assists in stabilising the bore especially in large diameter deeper piles.  It also allows the perfect insertion of heavily reinforcing steel cages. NSCC possesses the most modern fleet of large diameter heavy-duty rotary piling rigs capable of drilling to depth exceeding 75 metres.

CFA piles are a form of rotary bored piles but without the use of temporary casing and/or a drilling fluid.

A hollow-stem auger is rotated inside the top soil using the rotary drilling rig till the auger reaches the design depth or until resistance is encountered in consolidated soils or soft rocks.  Upon reaching the desired depth, the auger is rotated in the reverse direction and slowly lifted while at the same time lean concrete is pumped through the auger, thus replacing the soft soils with fresh concrete.  The process of drilling, lifting of auger and concreting is controlled through onboard computer controlled instrumentation.

Micropiles are small diameter foundation (300mm or less) elements drilled by means of small leader mounted rigs such as the Klemm KR 806 (modified) or the Hutte HBR 202.  Those small diameter structural elements are drilled fully cased through the use of segmental drill pipes to depths.  A high yield stress steel rods and then inserted into the fully grouted cased hole before the segmental casings are removed.

The use of micropiles becomes an advantage in situations where the use of larger piles is not recommended such as in soil conditions containing large boulders at depth, in areas where conventional rotary bored piles could affect the neighbouring structures or perhaps in low headroom conditions and/or karstic geology.  They can also be used to augment or replace deteriorating foundation elements or for supporting slopes, embankments or general soil stabilisation.

There are several types of micropile installation techniques such as ‘double rotary head system’, percussive system or rotary system with the assistance of drilling fluid or polymer.  Notwithstanding the method of installation, all micropiles rely on the friction between the grouted element and the soil/rock interface to resist the vertical loads.  NSCC has the experience with installing micropiles with a working load of 2500kN.

The use of low headroom micropiles use the same technique as micropiles but deploys a very small electrically powered drilling unit. Recently NSCC used such highly specialised drilling rigs to underpin the basement of a hotel in Dubai.

Barrettes are ‘rectangular’ piles.

Similar to rotary bored piles, barrettes are installed using drilling techniques under bentonite fluid or polymers that assist in maintaining the stability of the bore during drilling. Barrettes unlike bored piles are installed using crane or rig mounted diaphragm wall cutters and not drilling rigs. Barrettes often form the foundations of high-rise buildings and skyscrapers which are subjected to heavy loads and bending moments. Barrettes have the advantage over traditional rotary piles in that they can be installed to larger depths (over 100m) and take much heavier working loads.

Driven piles are one of the oldest piling techniques known to engineers.

It comprises of rigid structural elements driven into the soil formation till refusal is achieved. The piles in the form of square timber elements, circular or square precast or pre-stressed concrete elements are driven by means of hydraulic hammers into soft soils and form rigid inclusions into the ground that take moderate loads from overlying built up structures.
Driven piles are suitable for special applications where soft ground conditions such as alluvial clays (river deltas) or saturated silty sands are encountered. NSCC was the first to introduce piled foundations to the UAE in the early 1970s through the use of driven, precast and cast in situ piles. Preformed precast piles (circular or square) were driven into place using percussive techniques such as diesel and drop hammers, and later replaced with the more modern hydraulic hammers.
Cast-in-situ piles usually refer to the driving of tubular piles with a closed bottom shoe into the ground till refusal is reached. Upon refusal, steel and concrete are installed into the tube before its withdrawal from the ground.
Today, with more advanced piling and ground improvement solutions, this technique is hardly used in the Gulf anymore