Break solid granite like butter
Rio de Janeiro/Blumberg.
The suburb 'Leblon' in Rio de Janeiro is chic and popular -
and consequently very built-up. It is here that on the last
vacant site - a large granite massif - a large, modern
shopping centre with theatre, cine-centre and 240 shops
is to be built - 23 000 m² in area. But the whole hard rock
massif with a total volume of 30 000 m³ has to be
removed first of all in order to allow space for an
underground car park. It is here that hydraulic rock and
concrete splitting equipment from DARDA is playing a
leading role.
Because of the proximity of dwelling houses and
businesses, strict rules have to apply during the demolition
work: minimum noise and dust, absolutely no vibrations
and certainly no shock waves. Work can only be carried
out during the day, from nine to five, and no night or
weekend shifts. The use of hand-held rock and concrete
splitters from DARDA, in combination with diamond wire
saws, offered the best solution. Gigantic blocks, 10 metres
deep and 15 metres long are cut out and then broken up
with splitters.
Success through the alternative offered by the combination approach
The rock is first sawn horizontally in order to produce
strata or sections 1.5 to 3.00 metres high. Vertical and
lateral incisions are then made to divide the rock into large
blocks. These, however, must be further broken up to
enable removal off site, a process which is not really
commercially feasible using wire saws. This is why
DARDA's rock splitters are being used. Several pieces of
equipment, consisting in each case of a drive or power
source and one or more splitting cylinders, are in operation.
First of all holes are drilled at intervals of 30 to 40 cm over
the whole length of the block using drilling hammers.
The splitting cylinders are then inserted into the boreholes.
Using hydraulic pressure, a wedge is pushed forward into
the hole and forces the counter wedges surrounding it
against the inner walls of the borehole. If several splitting
cylinders are used simultaneously then this produces an
enormous splitting force. For example, four C12 N cylinders
together produce an effective splitting force of 14.028 kN
(1.432 tons). In a matter of seconds, a fissure appears
in the rock and the direction of this crack can be determined
in advance. Thus, the splitting process is absolutely
controllable.
The splitting cylinders are moved on and the process is
repeated until the block has been cracked along its entire
length. With single cylinders the whole block is further
reduced into smaller pieces of roughly 30 m3.
But even at this stage the blocks are too big to be transported
and so more splitters are used for secondary reduction.
The larger blocks are further reduced to a size of about
1 m³ until they can be removed off site with ease.
Environmentally friendly and controllable
The advantages offered by this method are clear: it meetst
he highest demands because the splitting process is quiet
and free of dust and vibration. Moreover, there are no pieces
of rock flying around in the vicinity. In a few seconds the
procedure has been completed.
Furthermore, about 20% of the whole mass of the granite
plateau is difficult to access and, therefore, the rock here
cannot be broken up using other types of machinery or a wire
saw. For the compact tools from DARDA, however, this
poses no problems and a substantial part of the rock was
removed using DARDA equipment alone.
Other methods of demolition which were considered at the
beginning did not meet the challenge. Hydraulic demolition
hammers would have caused too much noise, dust and
vibration. The use of expanding cement would have meant
a long delay between pouring in the cement and the
appearance of a crack and progress would have been too
slow. The hydraulic splitters from DARDA, in combination
with wire saws, won the day because of their 'soft'
demolition approach.
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