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Theoretical and experimental studies of ITH percussive drill vibration.pdf

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ã ã ã THEORETICAL AND EXPERIMENTAL STUDIES OF ITH PERCUSSIVE DRILL VIBRATION Ming Jian Department of Mining and Metallurgical Engineering McGill University Montréal, Québec, Canada A thesis submitted to the FacuIty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Engineering March 1994 © Ming Jia,n ã ã ã Abstract During underground, long-hole drilling operations, the bending of the drill string and
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    THEORETIC L ND EXPERIMENT L STUDIES OF IT PERCUSSIVE DRILL VIBR TION Ming Jian Department of Mining and Metallurgical Engineering McGill University Montréal Québec Canada A thesis submitted to the FacuIty of Graduate Studies and Research in partial fulfillment of the requirements for th degree of Master of Engineering March 1994 © Ming Jia n    bstract During underground, long-hole drilling operations, the bending of the drill string and vibrations in the system exert significant effects on hole deviation and penetration ratcs. Little prior research has been conducted in the area of the bending and vibmt.ions associated with ITH In -The - Hole drills. This thesis deals mainly with the modelling of the static and dynamic properties of the ITH drill system while drilling under such conditions. The bending of the drill string is the result of the string becoming unstable whcn its length or applied feed force exceeds a particular limitation. Undcr sueh conditions, lateral forces are created by the effect of the bendiu :, thus generating the hole deviation. The criticallength and {eed force of the ITH drill string before being unstabilized and its characteristics after unstabilization are studied. The vibrations, primarily the vertical vibration of the ITH drill string, are discussed with reference to both theoretical and case studies. By analyzing the static and dynamic properties of the drIll string, a continuous system mathematical model of the drill string has Lecn dcvcloped. Two different boundary conditions have been discussed and applied through computer simulations. Measnrements of downhole parameters and vibrations while drilling were acquired by a high-rate telemetry and data acquisition system from field tests of a CMS CD- 90B long-hole ITH drill and prototype shock absorber in an underground nickel mine. The vibration data was analyzed using spectral analysis mcthods and system identification techniques. Determining the inter-relationships bet,ween the drilling    ~ parameters, for example, feed force, torque, air pressure and pcnetration rat.e, and the vibrations in an ITH drilling system is also a principal objective of the tlH sis. he performance of a prototype shock absorber developed by a third party com pany was also evaluated through an analysis of the vibration modes present during the ITH drilling process to examine the specifications of a suitable shock absorber design. he results of the simulations and analyscs of the vibration data indicatc that a prototype shock absorber effectively reduces the amplitude of the vibrations, especially the vertical vibrations of the drill string. A mathcmôtical model usillg a complex boundary condition hM been developed which will be of use in furthcr research relating ta the development of a vibration-bascd control systeJ1l for ITI drills. hese results will not only be of use for dcveloping a shock absorber for thc CD-90B drill, but more importantly be applicable tn future research work on devcl oping advanced control for these drills. By decrcasing the vibration levcls acting 011 the drill head and rod, the instrumentation for an automated drill can be pl Otect.ed to ensure maximum life and proper performance during hammer operatioll .  1 ã ã esumé Dans les mines souterraines à base de métal, le forage des trous de production, en fonction des contraintes de l'emplacement et de la trajectoire, est essentiel pour réussir l'exploitation du minerai. Le résultat de cette phase d'extraction affectera de façon significative toutes les opération en aval, du chargement au transport, jusqu'au broyage et au bocardage. À cause de la nature même des foreuses utilisées, du type de minerai à extraire et de ia configuration de la mine, la trajectoire des trous peut dévier de façon importante par rapport à celle projetée au départ. Ces déviations peuvent entrainer une dilution substantielle du minerai et une perte de productivité, d'où l'augmentation possib1e des coûts d'opération. Les déviations ITH (dans-le-trou) des foreuses percussives, sont généralement causées par une courbure du foret qui plie sous l'effet des forces latérales présentes au niveau du foret ou le long de l'acier à foret. Dans cet exposé, on analyse les vibrations responsables de ces forces latérales. Cette analyse est fondée sur des études théoriques et pratiques réalisées sur le terrain. Pour ces dernières) le rendement des variables et des vibrations a été évalué à partir de l'observation d'une foreuse CMS CD 90B ITH dans une mine souterraine de nickel. Durant ces tests sur le terrain, on a également évalué le rendement d un amortisseur de chocs commercial et son impact sur Patténuation ou la transmission des vibrations générées par la foreuse. En analysant les propriété dynamiques et statiques du foret, on a élaboré un modèle mathématique de système continu capable de décrire son fonctionnement IV
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