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The Denison core barrel is a triple-tube swivel type corebarrel, with a shoe with a sharp
cutting edge threaded onto the inner barrel and extending below the cutting teeth of a tungsten corebit.
The length of the corebit must be changed to alter the amount by which the shoe extends below the
corebit. According to Hvorlev (***9) and Lowe (***0) a ****5 mm inner barrel protrusion is
suitable for relatively loose or soft soils, whilst the cutting edge should be flush with the corebit in
'very stiff, dense and brittle' soils. The Denison corebarrel uses a 'basket' type spring core catcher,
where a number of curved, thin, flexible springs are fixed to a base ring by rivets, or by welding.
According to Hvorslev (***9) the use of such thin springs means that the core catcher is frequently
damaged and must be replaced. The inner barrel encloses a liner, often of brass. The original inner
barrel design by Johnson (***0) had a *2% area ratio, and a 0.6% inside clearance. The use of a high
area ratio means that samples of hard clays and dense sands or gravels will be greatly disturbed, and
better sampled by a conventional retracted inner barrel type sampler. Very soft to firm clays can be
more effectively sampled with a fixed piston sampler. According to Lowe (***0) the Denison sampler
is designed for use in stiff to hard cohesive soils and in sands. It is rarely used in the UK, where stiff
clays are sampled using the **0mm thick-walled open-drive sampler, and the undisturbed sampling of
sands is rarely attempted.