had
-2-
'6
The movement only affected the top of the rock fill,
gradually dying out downwards, the base being unaffected.
Any water passing either through the core wall or
falling on the rock fill would be picked up by the two
under drains, and it was noted that after the movement had
taken place leakage developed.
It was feared that cracks had formed in the core wall
allowing water to pass through, some of the sand being removed,
the affect being to throw a greater pressure than had been
anticipated on the top of the rock fill, thus causing the
movement, but the exploratory work which has now been completed,
shows that this was not the case.
It had been anticipated that some movement would take
place when the reservoir was filled, and the core wall was
therefore provided with joints which were to be grouted when
this ceased.
EXPLORATORY MEASURES
It was decided to remove the whole of the sand wedge
so as to explore the downstream face of the core wall, and
this work has been completed with the result that only cracks
of a very minor character were discovered, coninciding
generally with the joints referred to above.
These cracks have been opened up at the downstream
face of the core wall in order to ascertain whether they were
merely surface cracks, or extended right through the wall,
with the result that it has not been possible to trace them
for more than a few inches from the face.
Although the cracks were barely visible to the naked
eye, it is probable that some slight percolation had taken
place, as the sand in the immediate neighbourhood of some of
the cracks was slightly stained. These cracks have all been
dealt with in such manner as to prevent any possibility of
percolation in the future.
/In