Geoscience Reference
In-Depth Information
Figure 6.1
Application of a geotextile container (filling, closure, releasing, falling).
6.2.2 Fillmethodology
A geotextile container can be filled with sand mechanically (by grab bucket) or hydrau-
lically (by pumps). Within the entire construction cycle filling is the major time factor
and so has to be performed relatively quickly. Dry filling is preferable to hydraulic
filling because it enables even filling and more air is contained in the fill material. The
significance of the air is discussed in 6.5.3. Dry filling also has the advantage of ena-
bling a steeper sand profile. This generates less width for the same filling volume, and
enables the geotextile container to move more easily through the opening of the split
barge during the drop. Filling must be spread evenly over the length of the geotextile
container. If not, during the drop, the geotextile container will shift unevenly through
the split barge opening, with one end passing through and the other end being impeded,
thus increasing the tensile stresses in the geotextile container (see Figure 6.2).
6.2.3 Fillmaterial
The grain-size distribution and density of the fill material play a key role in the design
process and the choice of the geotextile skin. Published literature [42] also refers
to geotextile containers that have been filled with dredged sediments for regulated
storage. However, in this manual the geotextile container is considered purely as a
structural element and always filled with sand.
The use of (clean) sand has the advantage that due to internal friction the material
can absorb more of the drop energy that is released during container impact on the
bottom. This reduces the possibility of geotextile rupture significantly.
