Home | Projects › Replacement of the Western Quay Wall of the river Waal, Nijmegen The Netherlands
Replacement of the Western Quay Wall of the river Waal, Nijmegen The Netherlands
|Project:||475 st AZ36-700 (new quay) and 525 st AZ26 (screen)|
|Location:||Nijmegen, The Netherlands|
|PVE 2350VM + PVE1000|
PVE 2335VM + PVE 800
|Data:||June 2013 - August 2014|
Discussions with Dieseko result in efficient progress
Men are working tirelessly on the Quay Wall in Nijmegen, to replace the 660-metre quay structure between Grotestraat and the railway bridge. Commissioned by the Municipality of Nijmegen and subcontracted by the contractors Colijn and Reef Infra, civil engineering contractor Gebr. De Koning from Papendrecht is replacing the much too short 12-metre quay wall sheet piles with 26-metre steel sheet piles. Before the replacement of the old quay wall can begin, a screen must be placed four metres from the quay to create a temporary construction pit. As part of the turnkey project, the main contractor is also replacing all of the anchors and the underlying sewerage system.
In June 2013 the first foundation rig, the Hitachi KH180, which has a lifting capacity of 50 tonnes, was transported to the western Quay Wall in the cultural city of Nijmegen on a pontoon. A series of vibration tests at different locations along the Quay Wall revealed that serious challenges awaited, because the ground contains a thick layer of boulder clay, comprising a tough, irregular mixture of clay, sand, gravel and large stones. This deposit is so incredibly heavy that even the 2350VM vibratory hammer was unable to penetrate it. Therefore the men from Gebr. De Koning decided to increase the weight of the vibratory hammers with ballast plates to create more downward pressure. In addition, they decided to inject fluid into the thickest layers of boulder clay. During this process, water is injected at high pressure under the piling point at a low flow rate. This increases the water pressure temporarily, causing the quay wall to collapse more easily.
Sophisticated vibratory hammer
In order to install the quay wall piles (weighing around 6 tonnes each), a large pontoon has been used, which has spud poles that enable it to anchor itself in the Waal River, which is famed for its very strong currents. A Woltman THW A-1200 PDS crane with a capacity of 120 tonnes per 4.2 metres was placed on the pontoon. A fixed king post with a sophisticated high frequency variable-moment vibratory hammer(PVE 2350VM) is hanging in this, powered by a PVE 1000 PowerPack that is fitted with the environmentally friendly AdBlue and fuel-saving Start-Stop system. The vibratory hammer is hanging in the king post amongst other things because this facilitates better control of the piles in the heavy layer of boulder clay. Crane operator Cees Hoekstra: “Piling from the pontoon requires a certain level of skill and must be performed carefully. The operator and the pile driver under the crane have to be able to trust each other blindly. I make continuous adjustments, so that the piles are driven into the ground as straight as possible.
“Normally, the PVE 2350VM has no trouble at all driving the 26-metre long quay piles down to the right depth in the ground,” says project leader Pieter Blom. “The pile analysis we carried out beforehand also gave us cause to doubt. But what we have encountered in the ground here so far surpasses all expectations. Aside from the layer of boulder clay, we have also found old stone quay walls, the remnants of the foundations of an old energy plant and, last but not least, 2000 years of history in the form of wooden poles with Roman pile points. And we've had to contend with contaminated soil, vibration and noise pollution and a dike that was in danger of collapsing. Amongst other things, we and the specialists at Dieseko have engaged all our options and knowledge to ensure that the works proceed as efficiently as possible for the client and as acceptably as possible for the environment."
The contract stipulated that the foundation work had to be finished by Christmas 2013, but the many obstacles in the ground and additional problems caused lots of delays. Therefore project leader Gebr. De Koning expects the project to take another few months.