| Although
the limpet dam is an ancient repair aid, being reputedly
used by Henry VIII for hull repairs on his fleet (and
still employed like that today), modern requirement
for sealing on irregular surfaces and considerations
of health and safety (not well established in Tudor
times), have called for refinements See
image 1.
This is inherently stabilising. However, it must also
be arranged that at all states of the tide, or emptying,
vertical sliding and rotational failures of stability
cannot occur due to the weight of the dam and upthrust
on it. Safety measures are taken including site specific
ones resulting from risk assessments and, although not
strictly necessary, a crane remains coupled to all dams
deployed.
The main force on a dam, once located and pumped out,
results from the hydrostatic pressure forcing the dam
against the structure. This is inherently stabilising.
However, it must also be arranged that at all states
of the tide, or emptying, vertical sliding and rotational
failures of stability cannot occur due to the weight
of the dam and upthrust on it See
image 2.
Other safety features are dualling of pumps, vertical
props, watchman and safety boat attendance which together
have given a near perfect safety record.
For more detail of limpet dam uses see:
Or watch the
video and animations. |
