Boulders - TSHD
Standard
When dredging in soils with boulders or boulder sized obstructions, a draghead needs to be fitted with a screen to prevent large boulders to enter the suction pump.
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The use of such a screen is necessary but will reduce the suction production drastically as the boulders will block the entrance of the draghead. When the production is too low, the first possibility is to lift the head and stop the pump to try to remove the boulders under water. This can help when the boulders fall out of the head. But this results in an important production loss. On top of this, the boulders fall back in the dredging area. This means that the boulders are encountered many times during the project.
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Mostly, part of the boulders will get stuck between the bars of the screen. In this case the boulders can not be removed under water and can only be removed by hand, after bringing the head on deck. This is very time consuming and dangerous for the crew on deck.
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Depending on the size and number of obstructions in the dredging area, dredging production can drop to very low values when using a standard draghead and screen.
