Reduction of the high levels of wastage in the
excavation of hard stone such as Portuguese pink marble was the focus
of a 27-month long BRITE-EURAM
project funded by the European Commission, and co-ordinated by the Business
Innovation Centre of Tuscany (BIC
Toscana) in Italy. The result was the design and construction of an
innovative diamond belt gallery saw for the underground excavation of
hard stone. A prototype was successfully tested at the Lugramar quarry
in Portugal, where it was shown to reduce wastage by between 30 and 50%.
Portuguese pink marble is currently excavated in deep,
open pit quarries. The process produces much wastage, particularly at
depths below 60 metres where the quartz-flecked stone is subject to higher
stress, causing fractures. In some cases, fractures can result in up to
85% of the marble being discarded. The waste and scrap materials left
behind cause disfigurement of the local landscape, while the lubricants
needed to operate traditional hydraulic-powered chain saw equipment used
to excavate the material also contaminate the environment. Safety of workers
operating the machinery is also an issue. Similar problems exist in the
open pit quarrying of stone in Spain and Greece.
Leading Italian quarry equipment maker Benetti
Macchine was commissioned to design and build equipment that could
excavate hard and abrasive types of marble such as Portuguese pink marble
(Mohs>3) more efficiently than the current technology. At the same
time, a feasibility study was carried out on the development of a faster,
more efficient block-cutting saw that could recover good quality material
from waste blocks already excavated. Tests were also carried out to find
ways of improving diamond tools used on all types of diamond belt machines
currently in use.
Benetti Macchine developed a specially designed
gallery saw for use underground, incorporating diamond belt technology,
capable of working on hard and abrasive types of marble with high
fracture characteristics. With the new equipment, galleries for
exploiting marble can be opened up directly from an existing open
pit quarry, thus limiting the need to excavate deeper where the
marble is likely to be more fractured. This means quarry operators
can now excavate horizontally rather than just vertically.
"It is a new way of exploiting the materials,"
says Laura Bertolucci, co-ordinator of consulting services to SMEs
at BIC Toscana. "One method of exploiting marble is open pit.
But the underground method is very important where the material
is heavily fractured. We can enter at a certain level and open a
gallery at the right spot for the best vein. It is more efficient
as you don't have to cut through fractured and waste marble to get
to the right spot."
The underground method is also safer and more
environmentally friendly. "Open pits create a bad impact, environmentally
speaking, because you have a lot of material wasted - you create
new mountains of waste material," explains Ms Bertolucci.
||Better working environment
Aside from exploiting better quality material
and producing up to 50% less wastage, the diamond belt technology
also increases productivity by requiring less maintenance than the
serrated chains currently used by gallery saws. The new equipment
also runs on water (using aquaplaning technology) rather than lubricants
such as oil and grease - thus reducing pollution.
As the diamond belt machines are completely
automated, operators can control the excavation by remote control,
which provides a safer and better working environment. The new technology
also allows quarry operators to increase their skills and job qualifications
and extends the opportunities for female employment.
Project partners included leading quarries across
southern Europe, such as Lugramar and Placido Josè Simoes
in Portugal, Felekis Bross in Greece and Granitos Rosa Valencia
in Spain. The Italian electronic device manufacturer CIEA collaborated
with Benetti Macchine on the development of the electronic panel
for the remote control of the new machine. Portuguese research institute
, Italian research group ENEA
and the ERICA Technological Laboratory also contributed their expertise.
This wide collaboration reflects the market
potential of the new technology in southern Europe. "The potential
is enormous in all countries which do not use underground exploitation
methods for the excavation of hard stone - such as Portugal, Spain
and Greece," says Ms Bertolucci. The Lugramar quarry had recently
bought, via tender, the diamond belt gallery saw prototype for use
in its operations.
But the potential does not end at European marble
quarries: the diamond belt technology could be used in construction
of urban metro tunnels or underground bunkers for nuclear power
plants where an absolute lack of vibration during construction is