Fascine mattress
A fascine mattress (Dutch: Zinkstuk, literally sink piece), is a large woven mat made of brushwood, typically willow twigs and shoots, used to protect riverbeds and other underwater surfaces from scour and erosion.
They are similar in construction to a fascine, but are primarily used for hydraulic engineering works, typically to strengthen the banks of rivers and streams, as well as coastal structures like revetments and groynes.
Modern fascine mattresses utilise a layer of geotextile in order to fulfill the competing requirements of water permeability balanced with the need to be impervious to sand.
[5] Zinkstuk have been used in The Netherlands for river and coastal engineering works since at least the 16th century, and were discussed extensively by Andries Vierlingh in his Tractaet van Dijckagie (English: Treatise on dike building), the manuscript of which was not published until 1920, and is now housed in the Nationaal Archief.
As Dutch dredging and hydraulic engineering contractors began to undertake works internationally, the workers earned up to 50 guilders per week overseas.
The manufacturing process of a traditional fascine mattress begins by winding rope around the willow in both directions using a machine, resulting in a lengthy roll known as a wattle.
[1][2][17][18] The mattress is assembled on a patch of ground adjacent to the water, and once the wattle is complete, the mat is towed to the desired location and sunk to the bed using dumped stones.
In The Netherlands, it is common to add tuinen, a type of fencing, to the top of the fascine mattress in order to prevent the stones dumped onto it from rolling off during underwater immersion.
As a result, the Deltadienst department of Rijkswaterstaat decided to undertake research and experiments at the Waterloopkundig Laboratorium, to investigate the possibility of improving the traditional mattress and reducing the quantity of brushwood required.
[20] This work coincided with the advent of synthetic geotextiles in the late 1950s and early 1960s, and traditional fascine mattresses began to reduce in popularity, with use being made of woven polypropylene fabrics in place of the reed underlayer.
[19][17] Modern mattresses are placed using civil engineering plant such as crane barges, long reach excavators and, in deeper water, side stone-dumping vessels.
The technique was also used in Zeeland for dike reinforcements in the Eastern Scheldt and in the construction and extension of the piers of IJmuiden and the widening of the North Sea Canal.
[48] In 1849, the British engineer Charles Blacker Vignoles visited Dutch contractors Aart Schram and Leendert Martinus Prins in Sliedrecht, and arranged for them to travel to Kyiv and install fascine mattresses as scour protection to the piers of the Nicholas Chain Bridge, which had suffered extensive damage during construction.
[51] Fascine mattresses continue to be used internationally,[52][53][54] including for bed protection works in Bangladesh, Vietnam, India, and Laos, particularly in the framework of development aid projects.
[55][56] One benefit of the method is that whilst these systems are labour intensive, they do not require significant capital expenditure, which is therefore an advantage in developing countries.
