Dredging is the removal of dirt (also called dredge) from the water bottom. This is often done with a large dredger, for example a cutter suction dredger.
Many different dredging techniques are available to remove the dredged material from the water bottom. Which dredging technique is most suitable depends on a number of different factors. These factors can be divided into 4 categories, namely:
In practice, several or a combination of different dredging techniques are often suitable for the dredging work. That is why often no technique is prescribed that must be used during dredging, but a number of preconditions that the technique must meet.
In this article we look at the conditions for each factor that the dredging technique must meet.
1. Dredging quantity
First of all, the size of the dredging work is important for the preconditions of the dredging technique to be used. This is because other techniques are suitable for large quantities than for dredging activities involving small technology.
In some activities, such as the construction of new works, sand extraction and maintenance of waterways, large areas of water bottom are dredged. The most commonly used techniques for large amounts of dredging work are dredging with the hydraulic crane, bucket dredger and various suction techniques.
When dredging material above a certain intervention value, the choice of dredging equipment depends on any effects on the water quality. The thickness of the dredging layer and the variation in it also determine which techniques are suitable.
It is important to have sufficient dredging components in stock for large amounts of dredging work. Dredge parts can wear out quickly. If a large area has to be dredged, it is therefore important to have sufficient back-up parts.
2. Location of the dredging work
In addition to the amount of dredging work playing an important role, the location of the work must also be taken into account. What is the accessibility, water depth, flow speed and dimensions of the waterway that needs to be dredged? Based on this, the conditions of the most suitable dredging technique may also differ.
3. The chemical quality of the dredge
The chemical quality of the material to be dredged also plays a role. During dredging, turbidity is created and spillage occurs. This can affect the quality of the water. It is therefore important that the discharge thereof is limited as much as possible. This has an effect on the requirements for the dredging techniques that must be used.
4. Accuracy of Dredging
When choosing a dredging technique, requirements are often imposed on the accuracy of the dredging. In many cases, dredging should not be too little, but also not too deep (too much). This applies to interventions in the sediment with a view to quality, but also to maintenance and construction.
Before dredging starts, it is important to map out these requirements. Based on this, the choice of the most suitable technique may also differ.
5. The composition of the dredge
The last factor that can influence the most suitable dredging technique is the physical composition of the material to be dredged.
If silt is dredged, a different technique must be used than when dredging sand or clay, for example.
Another factor that determines which dredging techniques can be used is the presence of coarse dirt in the dredge. The composition of the dredge can therefore have a significant influence on the most suitable dredging technique.