Amsterdam Quay Wall Collapse Sparks InSAR Interest
A SkyGeo Client Story
Public Safety at Risk
In September 2020, a security camera captured a 25-metre section of a quay wall along the Grimburgwal in Amsterdam, lean forwards and collapse into the canal.
For this failure to occur in the centre of such a busy city, demands that every government organisation and private company with responsibility for the public’s safety understands how it happened.
Since Amsterdam has over 800 kms of quay walls, the work we did was vital.
The collapse of the Grimburgwal quay unfolded in phases. It started with horizontal deformation that created holes in the paving and culminated in a vertical deformation that caused a section of the quay to detach.
The primary failure mechanism was identified as the horizontal load on an insufficient number of the 12-metre-long timber piles within the eastern part of the wall, caused be the canal being deeper at that point. While the work doesn’t explain the deeper canal bed, It is thought that repeated collisions of tour boats may have been a contributing factor.
Historical evidence, diving inspections, and the proximity to adjacent buildings supported the hypothesis that only two rows of piles were effectively functional in this part of the quay.
The renewal of the pavement in August 2020, prompted by prior quay deformations, was considered to be the trigger for the collapse. The role of groundwater flow, drought, and rain in combination with quay deformation was also noted.
The failure in the eastern section, dragged the western part with it, into the canal.
Our assessment emphasized the vulnerability of quays with short cap / floor constructions and only two rows of piles. Recommendations included prioritizing inspections of such quays, checking water depth, investigating masonry damage, and establishing a registration / notification system for subsidence issues.
The use of measurements derived from the expert analysis of Interferometric Synthetic Aperture Radar (InSAR) data, provided a good insight into the weakness of the quay wall section. Using these techniques, combined with historical data, it was possible to identify deviating settlements of the street behind the quay, long before the collapse.
Those vertical settlements were a result of the horizontal deformation of the quay, and so can be used as an indicator of possible future collapses. So, InSAR-based analysis can be a ‘stress test’ for quay walls and used to reduce the risk of collapse if managers pay systematic attention to settlements behind the quays.
The Grimburgwal quay collapse revealed a complex interplay of factors that contributed to its failure. While some aspects could not be definitively confirmed, they indicated avenues for further research and understanding. Our work underscored the need for continued development and validation of models for comprehensive structural analysis, as such models are not yet common practice.
Throughout this investigation, SkyGeo played a crucial role in sourcing and preparing the data required to analyze the collapse. Our expertise in data collection and analysis facilitated a more comprehensive understanding of the incident, aiding in the identification of failure mechanisms and contributing to the development of recommendations for the safety of Amsterdam’s quays.