Geoscience Reference
In-Depth Information
The mattress must be filled to the maximum fill density;
The mattress must make maximum contact with the slope surface;
For pulling or hoisting during installation the dimensions (length and/or width)
should be limited to restrict the tensile loads acting on the mattress;
Overlaps between mattress sections can be made by leaving 1 or 2 tubes of the
previous mattress empty (expensive) or equipping the previous mattress with a
sewn-on flap;
Always anchor the mattresses at the upper edge.
4.7 CALCULATION EXAMPLE
Given:
Bank protection has to be installed in a canal with shipping. A structure using
geotextile mattresses, as shown in Figure 4.5, is considered.
The following data are known:
significant wave height:
H
s
=
0.50 m;
peak period:
T
p
=
2.1 s;
flow velocity along the slope:
u
cr
=
1.5 m/s;
water depth
h
=
3.4 m;
slope:
α
=
1V:2.5H (21.8
°
);
porosity of sand:
n
=
0.40 [-];
density of sand:
ρ
s
=
2,650 kg/m
3
;
density of water:
ρ
w
=
1,000 kg/m
3
.
The geotextile mattresses to be used have the following properties:
tube diameter:
D
d
=
0.25 m;
average thickness of the mattress:
D
k
=
0.20 m;
Figure 4.5
Definition sketch of the calculation example for geotextile mattresses.
