Forming the foundations
Breakthroughs in foundation innovation are helping to improve build standards, finds John Bensalhia
There is no official rulebook when it comes to laying foundations for ports and terminals. Each port has different requirements and circumstances “because there is no “one size fits all” requirement", explains Nick Clarke, Ramboll's head of marine and energy infrastructure.
"We look at each port's needs. For example, there may be certain plant or materials that are available in the UK that are not available overseas. There may be particular operational constraints at a certain port. All of these factors gives you innovation with each project. There is no golden solution for all ports: each project depends on factors such as contractor skills availability and the ground conditions.
“Often choice of foundation is dependent on the ground conditions,” adds Ana Ulanovsky of Arup. “Cost effective foundations design should consider ground treatment options as well as heavier and robust structural foundations. Cost effective ground treatment is often of long duration and should therefore be considered at the early stages of a project to allow enough time in the planning of the works.”
While there may not be a universal solution, one rule comes through loud and clear, and that's innovation. Whatever the requirement, innovative solutions are being devised for ports in order to provide foundations that will stand the test of time in every circumstance.
“Our recent design of an automated yard on settling ground, led us to consider a range of foundations for both the crane rail foundations and the container stacks,” says Mrs Ulanovsky. “In an automated yard, the crane foundations have to meet strict tolerance limits to reduce downtime on crane operations. Automated cranes move faster than standard gantry cranes and rail misalignment in both plane directions can easily lead to a costly halt in operations.”
Mrs Ulanovsky says that among the options considered were ballasted troughs on piles that would significantly limit settlement and still allow for some flexibility to tamp the ballast if required. “Our final design solution was an inverted T-beam on piles with a sophisticated rail clipper that could accommodate vertical settlement via the use of rubber wedges and horizontal movement via a movable plate.”
Greater advancements in strength have had a positive effect on foundation work. Take the New Port Project in Doha, Qatar. AECOM has been involved in this project which is due for official opening in 2016. Work was recently completed on the quay wall, which comprises 224 pre-cast concrete blocks, each one weighing nearly 110 tons.
With projects involving heavy materials, time is money, and such a situation faced Ramboll for the Al Maryah Island development in Abu Dhabi. The client required a perimeter blockwork quay wall for the development. “Each one of the blocks is very big and very heavy, and requires careful handling,” says Mr Clarke. “Handling of these blocks would be very time consuming and a problem. We looked at what we could do to provide a cheaper, faster solution.
“We worked with Al Naboodah, the UAE contractor, to develop a diaphragm wall solution that would save on cost while producing an effective end result. The reinforced concrete fascia aesthetically matched up with the block work wall that was required by the client. It looks like a block work wall but at a more affordable price. In fact, it saved the contractor a seven figure sum as well as six months of work.”
A quick but effective solution is a circular caisson, which paid dividends at Jorf Lasfar port in Morocco. “Ramboll was tasked with rehabilitating and increasing six existing quays and constructing seven extra quays for a major upgrade,” explains Mr Clarke. “The client was keen that the new berths should have a flat face: instead of providing a diaphragm or combi wall, we provided a circular caisson which was more effective and quick to install.”
Arup's Ana Ulanovsky says that the use of caissons for quay wall designs can prove effective when, for example, the contractor already owns a caisson manufacturing facility or where ground conditions such as hard rock make piling techniques prohibitive. “To avoid displacements along quay crane rails spanning between caissons we have designed a beam on elastomeric bearings that can easily accommodate for movement without the need to re-level the rail.”
Another solution that enabled speedy completion occurred at Hong Kong's Kwai Tsing Container Terminals. For this project's design, AECOM used 32-inch diameter, open-ended steel pipes that ranged in length from 82 to 196 feet to support the structures. The next stage was to cap the piles with an insitu concrete grill deck with large precast concrete panels. The methods involved allowed the first berth to finish completion ahead of schedule: in fact, 18 months early.
When looking at foundations, ports must weigh up the initial costing of the project, and look at the best quality result that they can get at the best value price. “One of the cheapest solutions in the UK on a straightforward, no constraints level is the tubular steel pile Combi-Wall, which is a solution that is proposed for the Dover Western Docks revival,” says Mr Clarke. “We looked at all options for this project (including diaphragm walls, caissons and block work walls), and decided that this would be the most cost-effective solution.”
Additionally, when it comes to assessing costs, ports have to look at the bigger picture: “When ports look at cost, there is more to the price than just looking at the initial costs of the project. For example, if you have an operable port, you need to consider the impact that this will have on existing operations. You need to ensure that the project involves as little disruption to operations as possible, and in addition, the port needs to also consider a solution that is low risk and robust. For example, if a port is in an exposed location, then you want a solution that is resilient.”
It's vital that the daily routine of port operations is kept apart from the work. “Ports need to look at a constructive solution that separates ongoing operations from construction work,” says Mr Clarke. “During work, operating ports will have a contractor with large cranes, work boats and so on, so it's vital that these are kept apart from the daily routines, especially in cases where a leisure element is involved. There are also the normal “in service” health and safety issues to consider, for example, safety and life-saving equipment.”
Looking to the future, Mr Clarke believes that there will be no great change in the future of one of the key requirements of foundation building for ports, which is to produce the right method for the right location. "We are pushing great improvements in designs while lowering risk, disruption and cost,” he says. However, there is one notable current trend that will need to be borne in mind by ports: “Vessels are getting bigger and so the walls at the ports need to accommodate this.
“Getting the right combination is vital for successful infrastructure construction. Our focus is achieving this balance: the result is an excellent solution in terms of cost, performance and safety. The whole package then comes together to a very high standard.”
Strengthening the environment
Environmental concerns are an important priority in producing innovative foundation solutions.
“A key driver for innovation is the avoidance of noise and vibration from piling both with regards to its impact to people (e.g. local residents) but also due to its environmental implications and particularly impact on fish,” says Arup's Ana Ulanovsky. “Minimising the environmental impact of construction activities in an urban environment has led us to the design of a large dock retaining wall using innovative silent piling techniques to install 18m long tubular steel piles.”
Another example is the revamp of Johannesburg's Transnet City Deep Container terminal. One of the main aspects of this was to recycle over 10,000 m2 of the original surface concrete in order to achieve Transnet's targets for sustainability. Using Murray & Roberts Construction, one of the main innovations was a new geopolymer concrete and HVPFAC (High Volume Pulverised Flue Ash Concrete) to surface the terminal.
These solutions help achieve the aim of sustainability thanks to their unique properties. HVPFAC's combination of flue ash and mineral slag not only enhances strength, but also reduces water consumption. The geopolymer concrete's industrial by-products create a solid binder with the end game being a reduction of up to 90% in CO2 emissions.
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