Geoscience Reference
In-Depth Information
0.0
0.0
0.0
0.0
0.4
0.4
0.4
0.4
1.6
1.6
1.6
1.6
1.2
1.2
1.2
1.2
0.8
0.8
0.8
0.8
h = 2.0 m
h = 2.0 m
h = 2.0 m
h = 2.0 m
(a) large scale
1.2
1.0
0.8
0.4
0.6
(b) detailed
Figure 4.10 Pumping system for a building pit (horizontal view)
application 4.4
Consider a river embankment. The subsoil consists of three layers, from top to
bottom: a semi-pervious sandy clay layer (aquitard) with a height of
D = 2.5
m,
then a permeable sandy layer (aquifer) with a height of
H =
10 m, and next an
impervious clay layer (aquiclude), which seals off the groundwater flow. The dike
is considered impervious. The geometry is shown in Fig 4.11.
At three locations (A, B and C) a piezometer measures the groundwater pressure
in the aquifer (sand layer), for high water level:
h
A
= 4 m,
h
B
= 2 m,
h
C
= 0 m (
h
C
is
taken as reference, fixed water level in the hinterland behind the dike). The length
L
1
= 50 m, the length
L
2
is so long as to render the groundwater head at location C
practically unaffected by the seepage flow in the aquifer. The permeability of the
sand is
k
h
=
10
-4
m/s and of the top clay
k
v
=
10
-6
m/s. Determine the seepage under
the dike
Q
h
and the leakage through the aquitard (top clay layer)
Q
v
.
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