Slurry Cut-off Barrier
Of the several methods of creating cut-off barriers using slurry trenching techniques, Menard has successfully concentrated on the Soil Bentonite
method. This method makes use of a long arm hydraulic excavator to
excavate the trench under bentonite slurry, as seen in the photograph on the right at the Tempe
Tip site and which method is practical to excavation depths in the order
of 25 metres. Greater excavation depths can be accommodated, when
the excavator is supplemented by clamshell excavation, as seen below at the former BHP site in Newcastle.
The cut-off is created by backfilling the trench excavation following the
mixing of the excavated soil with added soil components to create a
backfill material with an appropriate particle size grading. These
additional soil components generally comprise of fine particle soils,
such as clays or in the absence of a source of clay, bentonite may be
used. Once the trench excavation has progressed sufficiently, the
backfill material is placed into the beginning of the trench and then
placement continues as the backfilling progresses along the trench in
pursuit of the continuing excavation.
