Project facts:
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Client
Municipality of Vlissingen
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Organisation -
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Implementation period 2015 - 2017
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Project budget > € 75.000
The challenge
The old slipwway in the Dokhaven is typical for the history of the city Vlissingen (Flushing). Huge ships were built and repaired here since 1875 by DAMEN Schelde Naval Shipbuilding. The slipway became historical heritage over the years and plans are initiated to redevelop the surrounding area into an residential area, which is called Scheldekwartier. The slipway consists of heavy concrete slope floors and walls, which are strongly decayed and severely degraded. The strength and overall stability of the concrete work is critical for the water safety, because the construction is part of the flood defence system.
Monitoring groundwater
Contractors discovered unstable ground layers in the Scheldekwartier during excavation work, possibly due to pore water pressure in aquifers. Water fluctuations, tide and foundation structures in the area had an adverse effect on the stability of the ground layers. Walhout Civil was contracted by the municipality of Vlissingen to install a groundwater monitoring network. All the groundwater levels and fluctuations in the Scheldekwartier were mapped out in detail. The results were combined with geotechnical analysis, whereby Walhout Civil has successfully advised the municipality in the most efficient groundwater management strategy.
Monitoring old slipway
The municipality of Vlissingen contracted Walhout Civil also for the monitoring of the slipways' concrete work. Cracks in the concrete work were monitored for more than a year, by use of hightec, digital sensors with GPRS/Mobile modules. The digital data is successfully read out and analysed by use of an online platform and crack analysis software. Further petrographic research and ASR-concrete research (core drilling, polarization or fluorescence microscopy) were recommended based on Dutch guidelines (CUR72 & CUR102). Dangerous alkali–silica reactions (ASR) has presumably been discovered in the concrete work. The safety of the flood defence system and overall stability of nearby bridges and road constructions are therefore critical. The results are now used for further research and another redevelopment of the area.
