The Netherlands: Construction of Maasvlakte 2 Running Like Clockwork
Since work started on the construction of Maasvlakte 2 two years ago, 170 million m3 of sand has been brought in. That is more than would be needed to fill the Rotterdam – Fyenoord soccer stadium to the brim 100 times. At the height of the ‘sand operations’, some ten trailing hopper suction dredgers were at work simultaneously.
Now, that number has been reduced to about three. Contractor PUMA (a joint venture between Boskalis and Van Oord) has shifted the accent in construction to the ‘stone operations’, or in other words the construction of 3.5 km of hard sea defences on the northwest side, and the construction of the quay wall for the first container terminal. Both are currently in full swing. This means that the project is on schedule. In three years, the first container ship will be able to moor in the new port area.
Important milestones in 2011 are the start of construction work on the quay wall for the APMT container terminal (January), the delivery of the site to container stevedoring company RWG so that it can set up its terminal (spring) and the construction of the infrastructure bundle (road, rail, cables and pipelines) to connect Maasvlakte 2 to the existing port infrastructure. This infrastructure bundle will be situated between the Slufter and Distripark Maasvlakte.
Blockbuster figurehead of Maasvlakte 2
On the northwest side, Maasvlakte 2 will have a type of sea defence that is completely new to the Netherlands: a stony dune, in front of which there will be a dam of large concrete blocks to form a breakwater. To position the biggest stones and the concrete blocks, PUMA designed a unique crane: the Blockbuster. This was assembled on site, tested exhaustively and recently started work on the sea defences.
The Blockbuster is a modified version of the so-called ‘E-crane’, which can position 40-tonne concrete blocks up to 50 metres from the heart of the crane with an accuracy of 15 cm. This precision is required to give the block dam a semi-open structure, so that the wave energy is absorbed. The sea defences must be able to withstand storms which only occur once every 10,000 years. The Blockbuster weighs around 1200 tonnes, has a counterweight of 360 tonnes and moves on three double sets of caterpillar treads.
The Blockbuster was delivered and the trial period began during the summer. The engineers from PUMA conducted tests with the various grabbers: for the 40-tonne concrete blocks, a special clamp was developed; the large chunks of hydraulic engineering stone are positioned using a polyp grab. The accuracy with which the crane works and the survey equipment that measures the Blockbuster’s operations were also tested exhaustively.
During the trial period, the crane operators were also given induction training. Although most of them were already very experienced in working with this type of crane, it is a different thing to operate a crane of this size and lift loads of 40 tonnes. The ‘final exam’ consisted of building a trial section ‘blind’: with closed blinds, the operators built a 50m block dam using only the information on the screen of the ‘crane monitor system’.
At the beginning of October, the Blockbuster drove onto the new land, its first task being to build temporary protection for the hard sea defences in the making. The aim of this is to ensure that as little sand as possible is eroded and as few stones as possible are washed away during the approaching stormy season. It is from this path that the blocks will be positioned in the final profile.
Stone dumping vessels, dumpers and shovels
On the southwest side, Maasvlakte 2 will have a soft sea defence of dunes and beach. On the northwest side, the waves can be stronger, however, and there is less room, due to the nearby navigation channel, to create a gradual slope. For this reason, it was decided to create a hard sea defence stretching 3.5 km made up of ‘stony dune’ with a block dam in front of it to form a breakwater.
Some 7 million tonnes of rubble and about 20,000 concrete blocks, each weighing 40 tonnes, will be needed for the stony dune and the block dam. The concrete blocks and 2 million tonnes of stone will be recycled from the old block dam and sea defences. 5 million tonnes of rubble will come from stone quarries in Norway, Scotland, Germany and Belgium.
On the sand core of the sea defences, the stone dumping vessel HAM 602 will construct a slope, with increasingly large stones as it gets higher. Plough boat Arca will profile the slope and the stone applied. From the land side too, stone will be applied. For this purpose, PUMA together with the firm Jac. Rijk is using various dumpers, shovels and cranes. By now, around 500,000 tonnes of stone from the water side and 700,000 tonnes from the land side have been applied. An equal amount is waiting in the depot.
At the moment, the Blockbuster is positioned on one of the two construction dams which protrude into the sea. The space between the construction dams will be filled up with stone so that the dams become part of the stony dune.
The progress of the construction of the hard sea defences is influenced strongly by weather conditions and the swell. The agreed milestones are still being achieved without any problem. If all goes according to plan, the sea defences will be complete in October 2012.
Quay wall for Rotterdam World Gateway
For the Rotterdam World Gateway (RWG) container terminal, two connecting quay walls will be constructed: a 1250 m deepsea quay (for the big container ships) along the Prinses Amaliahaven and a 650 m barge/feeder quay (for inland shipping and smaller container ships) at the top end of the terminal.
PUMA has outsourced this work to sub-contractor BAVO Kademuren, a consortium of BAM Civiel and Van Hattum and Blankevoort. The deepsea quay is an L-shaped concrete structure, the foundations of which are formed by so-called diaphragm walls, Vibro piles and MV piles. Work started on this quay in January 2010. At the moment, they are working on the quay wall over a length of 975 metres. The construction process takes the form of a small train: at the front, they start by digging grooves, at the end of the train the bollards are placed on the quay. In between, all phases of the construction process are visible.
The panels from which the diaphragm wall will be constructed are 38 m high, 1.2 m thick and 7.5 m wide. For these concrete walls, a groove is first dug using a backacter, a sort of grabber on long steel cables. During the digging, bentonite is poured into the groove. Bentonite is a mixture of water and clay and ensures that the groove does not collapse during digging. When the groove is deep enough, a meshwork of concrete reinforcement is hoisted in. Then, concrete mixers pour concrete into the groove. Per 7.5 m panel, about 300 m3 of concrete is needed. It is transferred into the groove, from the bottom up, using a filling pipe. As a result, the concrete presses the bentonite mixture upwards, where it is collected for reuse.
The diaphragm wall structure is largely below ground. In order to distribute the tensile forces of the quay structure, MV piles are being driven into the ground at an angle with the wall. At the moment, Vibro piles have been driven over a length of around 425 m and MV piles over a length of 375 m. In total, over 200 MV piles and more than 800 Vibro piles will be used for this container terminal.
On top of the diaphragm wall, the L-shaped wall will be placed. After applying the casing, the concrete will be cast in 25-metre sections. The first piece of L-shaped wall was cast at the beginning of October. Now, 100 metres are already in place.
In order to test whether or not the structure will be able to withstand the enormous force exerted by future container vessels, a tensile-strength test was performed on the MV piles, during which more than 92 tonnes of force was exerted. Ultimately, the structure will have to be able to withstand 72 tonnes. The MV pile bore the test without any problems.
The barge/feeder quay consists of a concrete wall, 7 by 3 m, on foundations comprising a combi-wall of tubular steel piles and steel diaphragm walls, with horizontal anchoring. The foundations for this quay have been built over the full length of 550 metres. The concrete wall will be built on top of these.
Recently, a start was made on the design of the working site for the APMT quay wall. In January 2011, when the front of the ‘train’ is ready with the quay wall for RWG, sub-contractor BAVO Kademuren will start work here on the construction of the deepsea quay and the barge/feeder quay for APMT, the second container terminal on Maasvlakte 2. Size-wise, this will be comparable to the RWG terminal.
Grass keeps sand in place
Not a golf course in the making, but fresh sand being brought to Maasvlakte 2. And that sand must not be allowed to blow away, of course. First of all, that would cause a nuisance in the vicinity. Secondly, it could even jeopardise the planned height of the Maasvlakte 2 site if a lot of sand was blown away by strong winds. The solution to this is simple: let grass grow over it.
On test plots on Maasvlakte 2, contractor PUMA has had grass sown. A plot sown with ‘Europoort’ mixture grass seed well known to connoisseurs, a plot with grass cuttings from the existing Maasvlakte and a reference plot. The grass cuttings not only contain grass seed, but also weeds. The reference plot has not been sown.
Ecological added value
The function of the grass is for its roots to hold the sand together. Whether or not the plot looks nice and green is of secondary importance. The Europoort mixture is known to produce good results. The aim of this trial is to find out if these new grass cuttings yield a comparably strong and sand-retaining result as the tried and tested Europoort mixture whilst at the same time producing varied vegetation. From an ecological point of view, that can yield added value if the more varied vegetation also attracts more insects and birds.
After the summer of 2011, they will take stock. Until then, the amount of sand that is blown off the plots will be measured using gauging rods. The ‘winning’ mixture will then be sown on Maasvlakte 2. The inner slope behind the new stretch of dunes, for example, must be covered with this, but sprayed-on areas where no building work is yet under way can also be clothed temporarily in green.
Source: maasvlakte2, November 5, 2010