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perfectly clear from the outer pipe.
REMEDIAL MEASURES
It is not possible to state what remedial measures
should be undertaken, until an exploration of the sand wedge
has been carried out to ascertain whether a cavity has
formed or not.
(a) It is advised that a line of holes be sunk in the
sand wedge at intervals of about 14 ft. to ascertain whether
cavities are met with and that such cavities, if encountered,
be filled as far as possible with "pea" gravel passed down
the tube to afford temporary support. It is possible that
the sinking of the tubes may bring about the collapse of any
sand arch which may be formed. The level in which water
stands in the tubes should be ascertained. The water
issuing from the outlet pipe referred to under paragraph (8)
should be kept under careful observation, a glass vessel
being provided to ascertain whether any fine sand is escaping
with the water. Should this prove to be the case, the
pipe should be plugged.
ALTERNATIVE I
Should it be found that cavities exist in the sand
wedge, the sand should be removed in layers of about 4 ft. at
a time, struts etc. being provided to take the thrust of the
Banking material, and "pea" gravel and small broken stone not
more than 3/8" in size should be substituted for the sand.
LEAKAGE
The excavation of the sand wedge will reveal cracks
which may have occurred in the corewall and these should be
made good by caulking if possible, or, if they prove to be too
fine, by placing a pad on the cracks strutted from the
rockfill by means of concrete.
grouted.
ALTERNATIVE II
The corewall should then be
Should no cavities be found in the sand wedge,