Geoscience Reference
In-Depth Information
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concentration (-)
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grain size diameter (µm)
Figure 5.4
Calculation of the sedimentation rate of sand in a geotextile tube.
(which is based on it). This is confirmed by numerical simulations where the initial
concentration of the sand-water mixture pumped into the geotextile tube must be
entered as the formula concentration.
As long as the geotextile still has a permeability comparable to the permeability
of the sand, the sedimentation rate will be higher than according to the calculation,
because there is double-sided drainage while the calculation is based on single-sided
drainage.
5.3 GEOMETRIC DESIGN
In Figure 2.1 a general design chart is given for geotextile-encapsulated sand elements.
The first step in the design process is to establish the functional and technical require-
ments. This is an area that falls outside the scope of this manual. As already indicated
in Section 2.2, it is assumed that the designer is already at the design process stage
and has a clear picture of the functional requirements, has a draft design of the entire
structure and wants to provide a more detailed design.
The main dimensions of the structure are established first. This is followed by the
size of the elements and the construction of the structure based on experimental data,
construction feasibility, economic feasibility and application area. Where possible,
this is done in consultation with the contractor.
A key component of the design of a structure using geotextile tubes is the choice
of the geotextile, which depends on the desired filter properties and the required ten-
sile strength. The filter function requires the geotextile to be adequately sand-tight
during use and adequately permeable during installation. In other words, the geotex-
tile has to prevent the sand washing away and enable the water to flow out.
