Geoscience Reference
In-Depth Information
Figure 6.10
Definition sketch of critical flow velocity over and along the structure.
6.5.7 Stackingstability
Geotextile containers can be stacked steeply into a bund (1(V):2(H) to 1(V):3(H)).
To build such a steep bund with containers special positioning techniques will be
required.
During wave attack, a pressure differential occurs between the water pressure
in the stacked containers and the external water pressure which may cause part of
the stacked containers to shear off and thus make instability a threat. Currently,
there is a limited amount of knowledge available relating to the stability of a stacked
structure constructed of geotextile containers under different hydraulic loads. The
Dutch Public Works Department has developed design criteria where a very conserva-
tive assumption is made on the distribution of water pressure that causes container
shearing to be of concern. However, field tests suggest that the distribution of water
pressure is less extreme and thus the stability greater. According to [15] container
shearing of is the most critical aspect for stacked containers up to approximately the
still water line. Container shearing can be a limiting factor with regard to instabil-
ity of the uppermost container (see 6.5.5) when the slope is steep and the container
is large in relation to the wave height. Also, the stability of the foundation can be
important, e.g. a soft clay foundation can deform considerably when a geotextile
container is dropped on it and can be susceptible to plastic deformations (squeezing)
and excessive settlements when a stack of containers is placed on top. This must be
assessed during the design stage.
