Geotextile tubes are a great way to dewater hydraulically dredged slurries as well as being used for structural applications like shoreline stabilization, island building, wave action dissipation, etc.
Geotextile Tube sizes and quantity are based on each specific project. Material being dredged is very important. If the majority of material being dredged is sand the consolidation rate in the geotextile tube will be minimal. If the material being dredged is a light fluffy organic material then very good consolidation rates should be expected and less tube volume per cubic yard of in situ will be needed.
When cubic yards of in situ to be dredged is established, material type is known, approximate consolidation rates are known, then a Geotextile Tube lay-down area needs to be figured out. Pairing Geotextile Tubes with the hydraulic dredge being used in the project is very important. When using larger high volume dredge pumps the larger the tube the better and several tubes need to be placed next to each other with quick turn on and turn off valves to maximize effectively. The larger the tube the longer it will take to dewater so this is also a factor when determining your project parameters.
Some dredge materials require a polymer addition to the slurry to obtain adequate dewatering. An example of this would be municipal biosolids and certain industrials wastes. Other times if the water quality criteria is such that the geotextile tube material alone cannot achieve the target goal then polymer will need to be added to meet those requirement.
Geotextile Tubes can be used with a wide variety of hydraulically dredged slurries such as river and lake sediments, industrial and municipal sludges, and sand. Geotextile Tubes can be used to dewater slurries or may be used in structural applications such as shoreline erosion protection. Geotextile Tubes used for dewatering are generally cut open and the dewatered material is either hauled off or spread on site. Depending on the material being dredged it is conceivable that the tubes may be cut open and hauled within 1 week of the completion of dredging operations up to several months until sufficiently dry. The size of the Geotextile Tubes are determined once it is established how much material is being dredged, the dredge’s pumping capabilities, and the available space to lay the tubes. The Geotextile Tubes need to be placed on relatively flat ground and measures need to be taken to control effluent being released from the tubes so erosion and turbidity are not a problem.
For more information on Geotextile Tubes and applying them to dewatering dredged material, please contract contributing blog writer, Tim Groh at [email protected] or visit his site at www.integratedwatersolutions.com Tim Groh is a supplier of Geotextile Tubes and provides consulting on dredging with tubes worldwide. Tim is also the owner of two hydraulic dredges including a 10 inch (254mm) discharge IMS Versi-Dredge®.
Contributing Blogger: Tim Groh