Geoscience Reference
In-Depth Information
head (water pressure 5 to 10 kPa). Consequently, the degree of filling is theoretically
between 81% and 87%, depending on the tube dimensions (larger tubes result in a
lower degree of filling with the same filling pressure on top) and whether or not the
filling is carried out above the water line (filling below the water line leads to a higher
degree of filling). Since the sand-water mixture volume decreases after filling, the
practical degree of filling is almost always less than 80%. A greater range has been
incorporated here to demonstrate how the degree of filling and the excess pressure
influence the shape of the geotextile tube and what its impact is on the maximum
tensile load. Figure E.2 also shows that when the degree of filling is higher, through
extra pressure applied during filling, this leads to an extra rise in the tensile load in
the geotextile.
One disadvantage with this method is that the pressure in the fill material and the
tensile load in the geotextile are used as input parameters with output in the form of
the cross-section of the geotextile tube. In designing geotextile tubes it is usual to use
the reverse approach where the circumference (or diameter) of the geotextile tube is
used as input in order to determine the required tensile strength of the geotextile as
output.
LESHCHINSKY (GEOCOPS)
Leshchinsky has translated the Timoshenko method into a computer program,
GeoCoPS [43], which can calculate both the tensile load in the geotextile and the
cross-sectional shape of the geotextile tube. Formulae for the tensile load in both the
circumferential and axial direction of the geotextile tube are given below. For further
details refer to [21].
For the tensile load in the circumferential direction around the geotextile tube
(see Figure E.3):
3
2
⋅
2
(
)
[
(
′
)]
p
x
+
y
(E.2)
T
=
p
0
′′
y
2
dy
dx
dy
dx
where:
′ =
and
′′ =
y
y
2
where:
T
=
circumferential tensile load in the geotextile tube [kN/m];
0
=
excess pressure (also known as pump pressure) [kPa];
ρ
=
fill density [kN/m
3
].
Because:
3
2
2
[
(
′
)]
+
y
(E.3)
r
=
′′
y
this formula is identical to formula (E.1) for
p
=
p
0
+
ρ
⋅
x
.
