Deep techniques

25 March 2008

An extensive foundation testing programme using PDA's from Pile Dynamics has been intergral to the s

An extensive foundation testing programme using PDA's from Pile Dynamics has been intergral to the success of Genral Floriad's largest road project to data in Orlando.

There is an interesting contradiction at the heart of the global market for piling and foundations equipment.

On the one hand, the market is truly global. Most products have few geographical limitations, and most manufacturers aspire to sell their products to as many difierent markets in as many difierent countries as possible.

On the other hand, the companies making these products are, in the overall scheme of things, small, specialist producers. In spite of their global reach, none has the financial clout or global manufacturing base of the major producers of earthmoving equipment, for example.

According to David Redhead, managing director BSP International, the explanation is simple, however.

“We operate globally, in fact our only major absence is the Latin American market,” he confirms. “And the fact we have a global spread even though we're a relatively small company is due to the ‘niche’ status of piling operations. For a start, there are probably only seven major manufacturers in our field (mainly hydraulic piling hammers but also dynamic compaction systems). Then, it's not a massive market in volume, but the crucial bit is that somewhere, someone will need these products.

“Also, companies don't buy in anticipation of maybe being able to use this kind of kit-they wait until they've got a job lined up and then buy for that job,” he concluded.

This global market then, is traditionally divided into two segments: driven foundations and bored or drilled foundations.

“I'd say hammers accounts for maybe 40% of overall piling market and the remaining 60% is drilled/bored piles,” added Mr Redhead.

Not that drilling and hammering should be seen as directly competing markets. “There are, technically speaking, places you can't use a bored pile, or it wouldn't be worth trying. Hammering is used for most work under water, for piers, for jetties, ports, oil rigs. It's used a lot for bridges over rivers as well.”

For hammer producers and users, there appear to be two key markets.

“The first is the extension or improvement or upgrading of established infrastructure in developed countries,” Mr Redhead continued. “There is plenty of work if not large volumes.”

One current example the company is working on is the extension of Brisbane port on the north-east coast of Australia. This requires the installation of 330 vertical and 31 raking piles to support the extension to the existing 372 m long container wharf. The work is being accomplished using the company's new generation CG210 hammer to install the vertical piles and an older HH1146 hammer to drive the raking piles and to achieve compression capacities ranging from 5000 to 7000 kN. Th ree pile diameters are being used: 1200, 1050 and 900 mm depending on the capacity required for each row.

“Then, in the developing world, there is the need to create the infrastructure in the first place,” he adds. “You need port or airport facilities before you can manufacture and export things, or before you can encourage tourism.”

The current health of the global infrastructure market is one of the reasons for a notable trend towards larger hammers.

“If there's a move in the market it's this: larger piles requiring larger hammers,” Mr Redhead explained. “Why? Ships are getting bigger, therefore ports need to be bigger, so piles need to be bigger-up to 2 to 2.2 m in diameter.

We've got lots of enquiries for big jobs refiecting this demand for larger piles.”

In response, BSP launched a new catalogue at Bauma detailing new available in ram weights up to 35 tonnes (the company's current largest is 25 tonnes). “They're not yet built, but we've been experimenting with our hydraulic systems to make sure they will work and we now have the ability to go up to 35 tonnes. We fully expect to get orders for these within next few months.”

Finnish rival Junttan has identified the same trend, and is using Bauma to unveil the HHK 25S, nicknamed ‘Little John', its largest ever hydraulic impact hammer,

It will have a ram weight of 2500 kg and a total weight of 4500 kg and is designed for driving large diameter piles (1420 mm with standard drive cap).

The company says the hammer is easy to connect to difierent hydraulic systems, is designed to be used with the 30CCU power pack and can also be operated by a separate power pack. It can be mounted on leaders, or can be freely suspended, while the design of the hammer frame and drive cap results in low impact noise and less vibration during piling.

In the boring and drilling market, there is an equally notable trend towards the other end of the spectrum: micro-piling.

Italian manufacturer Soilmec has recently launched two micro machines-the SR20 and SR30-which are proving popular in crowded, urbanised countries with plenty of brownfield development.

“There is certainly a lot of interest at the smaller end of the rotary market with the SR 20 and SR 30,” confirmed Robin North, managing director of Soilmec's UK subsidiary.

The is popularity touches on an issue that afiects all involved in the foundations market-their impact on the environment.

This manifests itself in a variety of ways, such as the concern about engine emissions that has lead to the widespread introduction of Tier 3/Stage IIIA compliant engines on piling rigs. The mid and top range of Soilmec's R series of rotary drilling rigs all now have Tier 3 compliant engines and more powerful and faster drilling rotaries ofiering more production than their predecessors.

Another emission that is often a cause for concern is noise. “There is a certain environmental impact of the noise generated by piling hammers, and this means bored piles are often used in more sensitive situations,” acknowledged Mr Redhead. “But you can do things, such as add shrouds and housings, to suppress the noise and make the process quieter, although not quiet. But then even drilling isn't quiet. It is quieter, but still not silent.”

Manufacturers such as Soilmec are aware of this issue, and the company recently launched an innovative vibro drilling attachment, mounted on an SM14, as a faster and quieter drilling alternative to normal top hammer drilling. This new vibro-rotary technology involves the vertical vibration of a normal rotary head and drill string and bit. The vibration efiectively reduces skin friction during drilling to achieve deeper penetration. “We have tested this vibration rotary on projects and the results have been incredible,” says managing director Simone Trevisani.

Then there is the generation of waste. “Just because drills are quieter than hammers, you mustn't assume there is no environmental impact of drilling,” pointed out Mr Redhead. “These displace the soil-hammering compacts it. Imagine putting in say 100 large diameter bore piles (e.g. 1.2 m) to 30 m deep. This means displacing around 33 m3 spoil per pile, that's 3300 m3 in total. You have to consider disposing of this waste, and the lorry movements required, to weigh up the environmental impact of this approach.”

Yet, again, manufacturers such as Soilmec are facing up to the challenge via noveld drilling bits for installing displacement screw piles. According to the company, the new tools reduce the amount of feed force needed and also considerably reduce the amount of spoil ejected from the hole. The concept is similar to that of the two main pile displacement tools which use a type of eccentric former on the bit that pushes and compacts the soil against the wall, thereby reducing the amount of spoil ejected at the surface.

“We are currently testing this on projects of our sister company Trevi,” said Mr Trevisani.

Of course, it is possible to create foundations that require no displacement, and which therefore generate no waste.

One such technique is mass soil stabilisation, a ‘simple’ idea, according to Mardi Ohanessian, president of the Allu group. “Just add binder to the material and mix it homogeneously,” he explained.

The Allu stabilisation system consists of three difierent units: power mix, pressure feeder for binder agent and the data acquisition and control system, and is a system that has been adopted throughout the world.

One recent example is the use of two complete ALLU PM/PF stabilisation units on a project in Florida wetlands of Key Largo, where the existing two-lane highway was being widened to a four over extremely wet, peaty and heavily vegetated ground-the only inhabitants in the area were crocodiles.

To achieve soil stability on the 15.5 km long by 11 m wide project the contractor used cement and furnace slag as binding agents, avoiding at the same time the replacement of theold soil.

In very difierent conditions, the company has also demonstrated the merits of this approach on the construction of a new harbour in Vuosaari, Finland, one of the biggest mass stabilisation projects in the world. In this project the sludge dredged from the sea is being stabilised in order to be re-used in the harbour construction.

According to Valto Tikkanen, managing director of Hyvinkaan Tieluiska, contractor on the scheme, there was no other reasonable working method for this area. “The first plan was to excavate and transport the waste soil away and replace it, but when TBT was found in the ground it made the replacement difi cult. It would have been like shifting the problem from one place to another. With stabilisation the contaminated soil is encapsulated into a solid slate preventing the pollution from dissolving in to the environment. The soil was also too muddy to be transported away with reasonable costs. In addition, the transportation from and to the site would have caused considerably more traed c, noise and harmful exhaust fumes.” iC

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