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Glenmaggie
weir is founded on the local bedrock. Concerns had been raised
as to the condition of the rock/concrete interface. This contract
was conceived by SMEC to investigate whether piezometric pressures
at the interface showed a correlation with the head of water contained
behind the weir
The
contract was between Geotechnical Systems Australia and Southern
Rural Water. Drilling and trenching were carried out as subcontracts
to Geotechnical Systems.
The
piezometers were installed in percussion-drilled holes at the
interface and backfilled with bentonite pellets and a non-shrink
cement grout. Cabling was led away from the holes in a channel
cut into the dam wall. These channels led to drill holes into
the main gallery and then to a central datalogger location.
The
datalogger used on this contract was a Data Electronics DT615
Geologger. Since the logging location was situated in the gallery,
away from the office area a telemetry system was employed to give
both access at the offices and a dial in option to allow SMEC
to collect and examine data. The logging frequency was daily with
alarm thresholds set to increase the logging rate in the event
of sudden changes in weir water level or piezometer reading.
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