A kubbestijl is a timber post set vertically into the ground to strengthen a lock or quay wall. It is a term from Dutch hydraulic engineering, used above all in combination with wulf walls: vertically built trough vaults found in lock chamber walls and quay structures. The word kubbe goes back to a part of a fish trap, the traditional fishing gear.
What the post does
A quay or lock wall is continuously pushed from behind by soil and groundwater. On the front, the counter-pressure of the water changes constantly as well — in a lock, within minutes. That load has to go somewhere.
The kubbestijlen form the vertical supports in that system: they stand with their foot in firm ground and take the horizontal thrust. The masonry wulf walls span between them, post to post. That way the wall itself does not have to be massive along its full length — a principle equivalent to vaulting in building construction, only lying down rather than standing up.
Timber in hydraulic works
Kubbestijlen are traditionally timber, and that works well under one hard condition: the timber must remain permanently below water, or below the lowest groundwater level. Without oxygen, oak or pine lasts for centuries. As soon as it dries out — through lowered water levels, dewatering works or a deepened channel — decay by fungi and bacteria begins, exactly as with timber pile foundations under old buildings.
When repairing historic locks and quays, that is therefore the first question: has the water level changed? Settling, bulging or cracking quay walls can almost always be traced back to the condition of the timber elements in the ground.
Related terms
- Revetment
- Sheet piling
- Perkoen pile
- Palisade
- Pile cap beam
- Retaining wall
- Timber pile foundation problems
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