Environmental Engineering Reference
In-Depth Information
Figure 20.14.
Piezometric conditions in jointed and sheared rock.
Figure 20.15.
Example of dewatering an excavation.
In practice most rock masses are very complex, and it is not possible to simplify the
model to the extent shown in Figure 20.14.
The geological factors which control groundwater movement must therefore be recog-
nised when installing piezometers and several piezometers must be installed so that the
critical condition can be defined. The piezometers should be installed with a permeable
surround, which intercepts the joints and bedding planes along which groundwater flows.
Dewatering an excavation
. Figure 20.15 shows an alluvial soil profile into which an
excavation has been constructed. The groundwater has been lowered by well points and
deep well pumps.
Monitoring of the effectiveness of the dewatering system, by installation of piezome-
ters, would be needed to check overall slope stability and heave of the bottom of the exca-
vation. To achieve this, piezometers would have to be installed in the silty sand and in the
