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Amsterdam’s 16th Century quay walls approaching the end of their lifespan?
 
Lifetime Extension Monitoring Spatial measurement

Kilometres of canals

When you think of Amsterdam, you immediately form an image of the canals. Kilometres of canals wind their way through the city. Most of these are very old and some even date back as far as the 16th century. The quays of these canals are therefore just as old and have wooden pile foundations. Not surprisingly, the walls built against these are in poor condition in many places and may have reached the end of their technical lifespan. To map the condition of the quay walls, Iv-Infra together with RPS and Bouwrisk is taking measurements to determine whether settlements are occurring in the 17-kilometres of quay walls and adjacent buildings that are deemed high-risk.

How are the quay walls behaving?

The municipality of Amsterdam is facing a major quay wall replacement project, in which 200 kilometres of quay walls must be tackled. But before a begin can be made, the state of the area must first be mapped. It is already certain that 100 quay walls, stretching 17 kilometres, are at high risk of collapsing. Part of the monitoring project is to examine how the quay walls 'behave' over the duration of a year. Are signs of deformation already present? And how great are the deviations? In addition, we also examine the damage sensitivity of neighbouring properties. Around about half of the quay walls have buildings located within 20 metres of the quayside and are present in the measuring catchment area. Iv-Infra monitors this by way of height measurements and determines whether the buildings are subsiding and how fast subsidence is occurring. This is how we generate an overview of the behaviour of the buildings under normal daily loads, such as heavy goods vehicles driving over the quayside. If the rate of subsidence is high, then there is reason enough for further investigation. Should these buildings have poor foundations, they could suffer major consequences when work is performed on the quays.

Monitoring in a busy city

“Monitoring quay walls and buildings in the centre of Amsterdam is quite a challenge,” says Marijn Bogers, Project Manager at Iv-Infra. “The quaysides are always crammed with cars, bicycles and people, so we often have to be creative with our measurements. People regularly walk through the sightlines of the measuring device and certainly when it’s busy by the canal, someone must always be present by the device. Because quaysides are usually full of parked cars, we often place the measuring device on a tripod between cars and bicycles or we use low prisms to take measurements under obstructions. And what about the houseboats located along the quay? These also require us, for example, to place extra points between them in order to help us arrive at a reliable measurement.” Marijn explains how often measurements have to be taken to ensure proper monitoring: “At most of the quays, we take a zero measurement and repeat the measurement three more times, approximately every four months. With the quay walls that are in bad condition, we measure once a month and repeat a further eleven times. A single high-risk quay is measured weekly for one year, which means we are continuously taking measurements with two to three people. In terms of size, a project such as monitoring quay walls is huge. It’s an immense challenge because no two quays are the same and you must continuously consider the very best solutions. Each quay experiences different conditions and the load also varies at different times.”

Measurements are knowledge

What happens with the measurements? The measurements we take are deformation measurements, relative X and Y measurements at the beginning and end of the quay. No deformation may occur between these points. We process this data in Excel into deformation tables and graphs and build a measurement report. All of this data is then sent to the municipality of Amsterdam. In the report, we also state whether settlements have occurred and whether deformation has been detected. Should the structural safety be at stake, then action must be taken. The hydraulic engineering department of Iv-Infra will then issue advice for the quay construction.

Would you like to know more about the possibilities for your project? Joost will be pleased to share ideas with you about this matter. Contact him via 088 943 3200 or send an email. 
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