Geoscience Reference
In-Depth Information
The negative value for
T
means that the geotextile mattress stays on the slope
under its own weight and that under these circumstances no tensile load occurs on
the anchoring.
Thus, the maximum tensile load occurs during hoisting. In reality, the upper geo-
textile will also contribute to the absorption of the tensile load. This is, however, not
assumed in the calculation above and the tensile load is absorbed by a seam, whose
tensile strength is 60% (this % depends on the type of seam and material used, see
section 2) of the tensile strength of the geotextile. The required tensile strength of the
geotextile is thus (conservative approach as the influence of surface friction is not
taken into account):
T
31 2
06
.
kN
T
se
T
am
52
/
=
=
=
geotextile
06
The available polypropylene geotextile has a tensile strength of 80 kN/m. For the
safety factor this means:
T
80
52
=
154
γ
=
=
T
T
geotextile
Stability in waves
In this example
H
s
is 0.50 m and formula (4.6) can be used to check the stability in
waves:
H
45
23
s
≤
Δ⋅
t
D
ξ
2
t
D
05
09802
45
15
complies
255305
382
≤
5
23
⇒
≤
3 05
382
⇒
.55
3
.
23
980
.
Stability in longitudinal currents
For the calculation of stability in longitudinal currents the Pilarczyk relationship,
formula (3.11), is used:
2
Φ
Ψ
K
T
u
Kg
s
⋅
K
⋅
Th
0 035
Δ
D
≥
⋅
cr
t
k
.
2
⋅
K
s
Stability parameter
Φ
=
1.5 (at the edges);
Shields parameter
Ψ
=
0.07;
K
T
=
1.5 (see Table 3.1).
