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THE INFLUENCE OF ROCK PROPERTIES ON THE EFFICIENCY OF MECHANIZED MINING WITH REFERENCE TO HARD ROCK CUTTING.

Ziel

THE AIM OF THE RESEARCH WORK IS TO DEFINE THE SCIENTIFIC BACKGROUND ON WHICH COULD BE BASED THE DESIGN OF NEW MINING MACHINES OR THE ADAPTATION OF EXISTING ONES FOR HARD ROCK CUTTING.
The experimental results led to interesting conclusions on the adaptation of moveable bits compared with fixed ones and on the superiority of a small cutting head (type ARH 22) compared with one with a maximum diameter of 0.6 m. In hard rocks such as Buxy calcite different cutting heads require different penetration forces. This explains why machines with a hammer action are power limited in hard rock.

Cutting machines today have considerably more power but their efficiency does not appear to have improved in the same proportion. Thereby, it appears necessary to adapt this type of equipment to hard or abrasive environments. This can be done by the development of new concepts for the cutting tools, for their fixing on the cutting head, for their lacing (ie the arrangement of the tools on the cutting head) and for the specifications of the machine itself. The optimization of all these parameters and, therefore, the success of machine cutting are intimately connected with the sustained effectiveness of the cutting process at the tool tip.
The aim of the work was to provide a sound basis for the application of current knowledge and practise to mechanized tunnelling in hard rock.
The results obtained show that rock cutting tests on a small cutter head, coupled with computer simulations, provide a reliable means of investigation into the cuttability of rocks for tunnelling applications. An important database has been obtained from laboratory testing using appropriate devices and carried out on 10 rocks (essentially limestones and sandstones). These rocks are characterized by experimental standard procedures. This database makes possible the estimation of the cutability of a given rock by comparing its standard characteristics to those of the subjected reference rocks.
THE RESEARCH WORK IS DIVIDED INTO SIX PHASES :

1.- ROCK CHARACTERISATION WITH RESPECT TO PICK OR DISC CUTTING
2.- BREAKING MODES DEPENDING ON THE QUALITY OF ROCKS, ON THE KIND OF TOOL, ON THE DEPTH OF CUT AND ON THE CUTTING SPEED. INTERPRETATION OF THE RESULTS WITH A THEORETICAL MODEL.
3.- INTERACTION BETWEEN NEIGHBOURING TOOLS AND APPLICATIONS TO CUTTING HEAD DESIGN.
4.- LABORATORY AND FULL SCALE TESTING
5.- DEVISING OF AN INTERACTIVE AND USER FRIENDLY SOFTWARE TO ASSIST THE ENGINEER IN DESIGNING OR ASSESSING A CUTTING MACHINE.
6.- WRITING OF A USER'S GUIDE.

IT MAY BE EXPECTED FROM THIS RESEARCH WORK THAT IT ENABLES THE EXTENSION OF THE MECHANICAL MINING TO HARD ROCKS WITH THE SAME ADVANTAGES AS FOR SOFT AND MEDIUM ROCKS.
IN COMPARISON WITH THE CONVENTIONAL DRILL AND BLAST METHOD IT WOULD RESULT IN :
- AN IMPROVEMENT OF THE SAFETY IN THE MINES DUE TO A LOWER FRACTURATION OF THE ROCK SURROUNDING THE UNDERGROUND OPENINGS
- A REDUCTION OF THE COST OF SUPPORT DUE TO THE SAME REASON
- AN INCREASE OF THE PRODUCTIVITY DUE TO A MORE SELECTIVE MINING
- AN ENHANCEMENT TO HARD ROCKS OF THE MECHANICAL MINING TECHNOLOGY.

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ASSOCIATION POUR LA RECHERCHE ET LE DEVELOPPEMENT DES METHODES ET PROCESSUS INDUSTRIELS
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