About Foundations, p2 (Piling)

An interesting article dated October 2004, taken from the publication Construction Week and posted at a Skyscrapercity.com forum provides an interesting look at the state of piling in Dubai's busy construction market. The article is posted in-full below. With regard to the upcoming work on the MAG 218 tower, the following excerpt is particularly interesting:

The most difficult aspect when it comes to the management of a project is time. Fast track is a term that is now synonymous with construction in the UAE and piling is no exception. “Many of the projects at the moment are challenging in terms of both time and quality,” says Karim. For the contractor fast track means that they have to deploy more resources (plant and human) as well as supervision to the site.

This raises the question of what kind of supervision will be present on site and whether some unavoidable delays may be preferable to having the project race along.

As to what kind of work may be expected to take place at the MAG 218 site, the following excerpt offers some clues:

The range of services offered by piling contractors does vary but broadly speaking they include: bored piles (rotary) – used for the larger structures under heavy loads; bored piles (CFA) – used for the smaller buildings; retaining structures – used for underground parking mostly, sheet pile walls; post and plank walls; contiguous walls; secant walls; and diaphragm walls.

The MAG 218 tower will have as many as three underground floors for parking, so it will be interesting to see what kind of wall structure is selected.

See Asking the Right Questions (About Foundations, p1)

New towers pile on the pressure
When it comes to piling, Dubai is probably the busiest city on Earth. “The rapid growth of Dubai as a city, the UAE as a nation, and the Gulf as a region has meant that there is probably more piling work here than anywhere else,” says Mustapha Karim, managing director, Swissboring. Despite the large volumes of work, the scramble to bag contracts remains.
“The market in foundation engineering is best described as bullish and the best it has ever been, but this comes at a price. The expansion in the market has meant that many companies have opened shop ranging from experienced professional companies with proven track records to one-man-show operations. The fast moving market has left many companies with no alternative but to grow, the question is how fast and effectively can a company grow versus how long will this bullish market last,” says Nidal N. Khoury, director, corporate management, NSCC.

When asked by CW how long the current boom period would last, Khoury says that the prospects remain healthy for the time being with many in the industry forecasting three to five years of solid growth. “There are many exciting aspects to this market in that the projects are larger, requiring more resources and supervision. This is great for foundation engineering as it allows companies to be recognised as specialist contractors as opposed to simple subcontractors.”
partners

“There are many more main contracts to be had as forward packages as well as other opportunities of partnering with main contractors on the more sophisticated projects where both our and our competitors’ skill is key to success (and not a commodity),” says Khoury. “Moreover, there are also the traditional subcontracts that allow companies in this industry to choose their path as they see fit. In the end, it is about choices and having them is always best,” he adds.

Piling work is normally undertaken as a separate main contract, a joint venture with a civil contractor or as a subcontract with each method requiring a special degree of attention. Although the work remains fundamentally the same, the piling work will be managed differently, including the risk, resource allocation and other project attributes.
difficult

The most difficult aspect when it comes to the management of a project is time. Fast track is a term that is now synonymous with construction in the UAE and piling is no exception. “Many of the projects at the moment are challenging in terms of both time and quality,” says Karim.
For the contractor fast track means that they have to deploy more resources (plant and human) as well as supervision to the site.

The range of services offered by piling contractors does vary but broadly speaking they include: bored piles (rotary) – used for the larger structures under heavy loads; bored piles (CFA) – used for the smaller buildings; retaining structures – used for underground parking mostly, sheet pile walls; post and plank walls; contiguous walls; secant walls; and diaphragm walls.

“Bored piles are preferred to driven piles in this increasingly high rise market because you can place larger loads onto a bored pile. Driven piles may be suitable for smaller structures if there is nothing to obstruct pile driving,” says Derek King, divisional manager – piling and ground engineering division, Ducto Balfour Beatty Group. “Apart from material costs, one aspect that can determine the shift from driven to bored piling is the ground conditions, and especially the known or possible presence of shallow obstructions. You usually have to get a certain minimum length of a driven pile embedded into the ground. If you have a shallow obstruction to driving, like a boulder layer or cap rock, piling becomes a lot more expensive because you have to prebore at each pile location before driving the pile,” he adds.

In city areas another consideration is noise. “Bored piling has the upper hand in city areas because driven piles require heavy equipment and hammers that produce a level of noise that is simply not tolerated close to where people live,” says Karim. One area where driven piling does command a far larger market share is marine work. “Driven piling either as tubular steel piling or driven steel beams and sheet piling are widely used and more common for marine work,” says King.
limited space

As the region continues to grow space will become more limited which means buildings will have to be taller, basements will have to be dug, all of which require more piling work. The numerous large towers under development in Dubai are a direct result of the limited space and will require extensive piling work, typically using bored piles ranging from 800 mm to 1500 mm in diameter. In other markets, piles that are 3000 mm in diameter are sometimes used where the loads are particularly heavy, for example at the core of buildings around the lift shafts. They may not be used to support the entire building, as slightly smaller piles can be used on the building’s periphery where the loads aren’t as high. These very large piles are not used as much here because building footprints are big, which means that loads can be spread onto more piles.

These buildings present considerable challenges when it comes to piling. “New technology is not as easy to come by in our industry, it is a traditional business where most of our work supports structures that are getting taller, slimmer and faster track.

Most new technology comes in the shape of machinery and the manufacturers have done a fabulous job developing more powerful and adaptable machines to suit the severe weather and working conditions in the UAE,” says Khoury.
On the other end of the scale, a significant amount of growth for the market is expected to come as medium rise buildings that did not require piling before grow taller and need more foundation work. “It’s very hard to give a generalisation because its dependent on ground conditions. But once you cross about three to four storeys you have to start looking at small piles,” says King. “Cost is another major consideration, very big raft foundations where the whole foundation is basically just a big slab of concrete can be used for smaller structures, but with concrete and steel being so expensive at the moment the piling option maybe more cost effective,” he adds.

All these trends suggest that the market for piling contractors will remain buoyant for at least the next few years. “Right now I would say there are more than 250 piling rigs in Dubai. This indicates that the market is growing very fast, and it continues to beat our expectations and forecasts in a positive way,” says Karim.

Whether the market continues on its current trajectory is anyone’s guess, but everything would seem to suggest that the conditions are good, but just as any ground engineer will tell you, there are always a few surprises.

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