SOIL AND GROUNDWATER - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 63

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 .