Geoscience Reference
In-Depth Information
Design charts for the geotechnical
stability of geotextile mattresses
and geotextile bags on slope
revetments
A wave load on the top layer of a slope revetment continues on into the subsoil.
The wave transmission is muted and delayed because the water in the pore space is
elastically compressible. This causes fluctuating negative and positive pore (water)
pressures in the subsoil and thus a corresponding increase and decrease in effective
stress. This phenomenon is called elastic storage and can lead to shearing of the sub-
soil. The stability of the subsoil can become critical if the elastic storage causes a
decrease in the effective stress to such an extent that the ratio between the shear stress
and the normal stress exceeds tan(
φ
) of the subsoil, where
φ
is the internal friction
angle.
For the criterion of shearing of the subsoil design charts have been drawn up for
the most common situations (see Figures C.1 and C.2). In these charts the maximum
allowable wave height has been plotted against the thickness of the top layers, for
different slope angles. The design charts are applicable to geotextile mattresses and
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0.1
0.2
0.3
0.4
Equivalent thickness top layer [m]
0.5
0.6
0.7
0.8
0.9
1.0
Slope 1:5
Slope 1:4
Slope 1:3
Slope 1:2
Figure C.1 Design chart for shearing of subsoil for S op = 0.03.
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