SMALL DAMS PETITS BARRAGES

Water Level Sounder - Details of the water level sounder are shown on Fig. 6.5 and
6.6. This device is comprised of a suitable length of ¼ inch coaxial cable or tape, fitted at the
ends to contact the water surface in the plastic riser tube and for connection to an ohmmeter.
Fig. 6.5 – Water level sounder for standpipe piezometers.
Pore pressure cells give precise localized measurement and offer faster response
times than standpipe piezometers.
Fig. 6.6 – Different models of vibrating wire piezometers.
The vibrating wire piezometers has usually a thick-wallet stainless steel housing to
prevent the vibrating wire transducer from responding to total stresses acting on the housing, a
very robust and water-blocked signal cable, heavy-duty seals, and long high air entry filters.
They are good instruments to measure the pore water pressures at the foundation or at the
earth embankment with permeability coefficient equal or lower than 10 -6 cm/s, for long-term
survivability, usually about 30 years.
Displacement Measurement
Measurement of the absolute displacements of the dam’s survey targets with respect to
fixed benchmarks (Fig. 6.7) set up in zones that are not likely to be affected by any significant
movement; altimetric measurements (settlement) and planimetric measurements (upstream-
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