1,721,016 research outputs found
Optimising quarrying techniques and practices
No full textThe European Regions, today rather poor in metalliferous and energetic commodities which could be economically exploited, are, on the contrary, naturally rich in natural stone resources. Ever since stone has represented in Europe a very important resource and, indeed, it is a part of our historic-artistic heritage, as its use as a construction material still characterizes and adorns most of the public and private places throughout European cities. It is important to point out that many natural stones have today a "cultural" value: they may be considered as "classics", as they have been exploited since antiquity and are element of the architectural heritage of many Countries. The stone industry is a very significant activity in Europe, as a consequence of the geological set but also of the mentioned strong tradition in quarrying and using natural stone; dimension stone quarrying represents a traditional and important economical activity, source of wealth and employment. The production system shows great variations in size, level of industrialisation and technological application, but it is mainly represented by very small enterprises: production units down to 500 m3/year can be still viable. Stone products of excellent quality are still obtained both using simple traditional tools and manpower and highly sophisticated machines. However, dimension stones generally have an international market, with a worldwide outlet, getting high unit prices, which can balance the high production costs typically faced by quarrying enterprises. Despite its very long tradition, stone sector is a very dynamic industrial activity: it has been progressively modernized in order to meet more advanced extractive and processing technologies, thus contributing to higher levels of production and quality, and increasing competitiveness in stone markets. Furthermore, ornamental stones sector is important not only for the primary production of stone materials but also for the industry of processing and building application, and the connected very important industry of quarrying and working technologies. Worldwide stone production and use are steadily rising, marking a 7% average growth during the last twenty years and reaching a total raw production of about 77 Mt in the 2002. Europe still covers the 45% of the world stone production and shares the 35% of the stone consumption, keeping a leading role in this sector. Nevertheless, European stone quarrying industry has to face important challenges: on the one hand, the stronger and stronger competition by low-labour-cost Countries (first of all China, India, Iran, Brazil) and, on the other, the respect of rigid environmental regulations and restrictions. Social attention to environmental aspects, steadily increasing in European Countries, has been leading to a stricter regulation of many productive activities: among them, mining and quarrying sectors have been often censured for their potential and real impacts on land and environment. Actually, it can not be forgotten that an intensive quarrying activity is land "invasive" and causes a concentrated environmental pressure. Referring to dimension stone exploitation, quarries are often grouped in extractive basins, where the resource is localized with suitable quality and quantity: this fact has sometimes raised critical environmental situations. Actually, very restrictive environmental protection policies have led to severe limitations to quarrying activity, but the results do not seem to be completely positive in terms of sustainability: on the one hand, closing-down stone quarrying activities imposes a shrinkage in local social and economical development; on the other, quarrying activity is pushed towards developing Countries, environmentally un-protected, simply moving and putting off to next future the problem. Finally, the sector relevance demands the research of a sustainable balance between social-economical productive needs and environmental protection. These aspects bring to the problem of the sustainable development of the stone industry: "reconciling the need for more secure and less polluting extractive activities while maintaining the competitiveness of the industry". The target is quite complex but, of course, challenging to develop new solutions, which should include effective legal frameworks, suitable technologies and careful plannin
Rock cutting by diamond tools: an experimental research
No full textRock is a random-composite material, and rock cutting diamonds are randomly shaped tools. Based on this, a research program has been planned, starting from single diamond operation on actual rock specimens. Points to be elucidated are the forms of the mathematical linkages between cutting force, normal force, cross section of the kerf produced and rock micro-hardness; the last point, due to obvious scale effects, does not seem to be reasonably predictable from conventional geo-mechanical tests and macroscopic scale cutting tests, nor from conventional rock mechanics theories. Following a synthetic discussion of the problem, the experimental apparatus is described and the results of tests under different conditions are presented. These tests cover the range of the normal and tangential forces applied by a single diamond of a wire saw bead, on different rock types. The results are then analysed, and a mathematical model of the single diamond action, in a form suitable to the application to a simulation of the multi-diamond cutting tool, is presented. In the meantime, the most suitable way to characterise the rock in diamond cuttability problems is discussed and, in particular, the problem of obtaining quantitative micro-strength distribution data from conventional mineralogical-petrographic description is treate
Loading and haulage in quarries: criteria for the selection of excavator-dumper system
Full text linkThe optimisation of loading and haulage is one of the most important issues for the yield of quarrying activities. Many external factors may affect loading and haulage system selection: amongst them a very important role is played by local topography, stability conditions, size of the
excavated material and capacity of the crusher.
Of course, loading and haulage equipments affect
one another and should be matched in order to get an efficient system, considering both production
and economical aspects; selection criteria should be mainly based on:
optimisation of loading system (sometimes working as excavation equipment too);
optimisation of haulage system (in terms of both single equipment and fleet);
optimisation of maintenance programs and organisation (in terms of availability of the system).
In particular, the paper deals with the hydraulic excavator – dumper (or truck) system, focusing on the relations between the technical characteristics of the equipments. Many loading and haulage operations have been analysed in different Italian open cast mines and quarries, in order to identify the best working relations and to derive a simple procedure for a proper selection
An example of preliminary seismic survey to evaluate the feasibility of blasting works in proximity of a sensitive monument
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Il giacimento di Quarzite di Barge sul Monte Bracco: criteri di prospezione, tecniche di coltivazione ed utilizzo di sistemi informativi finalizzati alla valorizzazione della risorsa
No full textNoise and dust emissions from mining activities: A software for a first approach to the measurement management and selection of suitable reduction techniques
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