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Graphic element Research > Growth > Research projects > Products & processes projects > Thanks for the memory
Graphic element Thanks for the memory

Two-thirds 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.

From antiquity 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.

Most quarries 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.

A ready-made idea for Europe

When 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 them."

A 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 CRAFT project was born.

In addition to Ripamonti and D'Appolonia, eight SMEs from Italy, Spain, Portugal and the UK have been involved in the project. The UK's Brunel 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.

Putting memory to good use

Shape 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.

The 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 cost-effective.

There 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.

  Two parallel developments continuing

Results 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.

Although 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 stone.
  • The second is to investigate the potential of the technology for other related applications, such as demolition, tunnelling and mining.

After 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.

For 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 Europe.


A ready-made idea for Europe
Putting memory to good use
Two parallel developments continuing

Key data

Improved mineral extraction methods form part of the Innovative products, processes and organisation key action. This CRAFT project has developed a safer method of splitting ornamental stone blocks which has the potential for worldwide commercialisation.

Project: Application of SMAs in quarries for a novel splitting system (BRST-CT98-5186)

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