of the world's marble is quarried in Europe using techniques that have
inherent dangers, such as drilling and blasting. Alternative extraction
methods do exist, but these are prohibitively expensive for use by SMEs.
This CRAFT project developed an innovative splitting system for ornamental
stone quarries using shape memory alloys (SMAs) to generate directional
forces. Several prototypes have since been built and theoretical predictions
have been confirmed by both laboratory and field tests. The result is
a safer and more cost-effective quarrying method that can be easily integrated
into the existing working procedures.
to modern times, the beauty of polished marble has ensured its popularity
with both architects and sculptors. Today, two-thirds of the world's marble
is quarried in Europe, particularly in its southern regions, and of that,
two-thirds comes from Italy alone. Quarrying is laborious work. Large
blocks up to 40 m3 in size are first extracted from the bedrock, and then
split into more manageable blocks of 3 to 5 m3.
use stitch drilling to extract and split the blocks. This method involves
drilling a series of holes along the rock's natural splitting line, and
then either using 'soft' explosives or hammering in wedges to force the
rock apart. There are obvious dangers in any task involving explosives
and, furthermore, the resulting dusty environment has associated health
risks. Alternative methods do exist but most require specialist equipment
and supplies, and some, such as diamond wire cutting, are too expensive
for SMEs to consider when tough materials are concerned.
ready-made idea for Europe
Stefano Carosio of the Italian technology transfer company, D'Appolonia,
read a magazine article about the potential use of shape memory
alloys (SMAs) for quarrying, he immediately realised it would be
an ideal project for a European consortium. He says: "The Japanese
toyed with the idea but, for various reasons, didn't pursue the
research needed to develop a commercial product. Given Europe's
dominance in the marble market, I was confident that the necessary
skills and drive existed here - it was simply a case of locating
conference brought him across the path of Dr Gianni Ripamonti whose
company has been manufacturing mining equipment since 1970. Dr Ripamonti
was extremely enthusiastic about the idea and, as a supplier, also
had the necessary contacts to put together a consortium of SMEs
to develop the concept. With Mr Carosio able to draw in the necessary
research partners to provide additional technical expertise, the
project was born.
addition to Ripamonti and D'Appolonia, eight SMEs from Italy, Spain,
Portugal and the UK have been involved in the project. The UK's
Institute for Bioengineering is a European Centre of Excellence
on advanced applications of SMAs, in particular as far as the space
domain is concerned, and provided essential technical input and
a problem solving approach. Two other specialist organisations -
Spanish natural stone consultancy Informstone
and Duomo, a non-profit organisation dedicated to the maintenance
of Milan Cathedral - also joined the project.
memory to good use
memory alloys have been known for over 30 years, but only recently
are they finding applications in a range of industries. As their
name suggests, they 'remember' the shape in which they are originally
formed and will return to it if not constrained in some way. The
main work of the project was the development of large SMA 'actuators'.
These consist of small cylinders of SMA that are activated by heat
generated using lightweight portable batteries.
strong forces generated by the SMAs as they return to their original
shape can be focused far more than those of soft explosives. So,
although some drilling is still required, far fewer holes are necessary
than with conventional stitch drilling, saving the quarry both time
and money. In addition, the SMA can be re-used, which makes it extremely
are also a number of other operational advantages with the system.
The improved control means it is possible to extract a block of
marble that has a perfect shape and dimension, and which has not
suffered any internal damage due to explosive forces. The splitting
method also provides a smoother outer surface, reducing the need
for finishing operations and the amount of waste material. Work
can also continue on other tasks in the quarry while splitting is
taking place whereas quarries have to be cleared when explosives
are being used.
parallel developments continuing
from the 18-month project have recently been presented at a conference
in Lisbon, and a patent is being filed to cover the key parts of
the new technology. Several prototypes of the system have been manufactured
and tested with small-scale blocks in the laboratory and full-scale
blocks in the quarry. These tests were successful and were in close
agreement with the analytical and numerical simulations that had
previously been carried out to predict the behaviour of the SMA.
the CRAFT project has officially ended, the partners are continuing
development along two parallel lines:
The first is to commercialise a simple system for
use not only with marble, but also with other types of ornamental
The second is to investigate the potential of the
technology for other related applications, such as demolition,
tunnelling and mining.
further work on the alloys is completed, a product should be launched
in the stone quarry market in 2002 to 2003, for which initial sales
of 300 to 500 units could be expected.
the SMEs involved in the project, access to the new technology offers
them a competitive edge, as well as providing safer working conditions
for their employees. For Ripamonti, the technology will be an extremely
valuable addition to their existing equipment line. The system is
believed to be unique, and sales have the potential to extend outside