ebook img

Wear of rock cutting tools: laboratory experiments on the abrasivity of rock PDF

153 Pages·49.432 MB·English
by  DekethH J R
Save to my drive
Quick download
Download
Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.

Preview Wear of rock cutting tools: laboratory experiments on the abrasivity of rock

WEAR OF ROCK CUTTING TOOLS LABORATORY EXPERIMENTS ON THE ABRAS!VJTY OF ROCK Taylor & Francis Taylor & Francis Group http:/taylorandfrancis.com WEAR OF ROCK CUITING TOOLS Inboratory experiments on the abrasivity ofrock H.J.R. DEKETH Technical University Delft, Section Engineering Geology, Delft 0 CRC Press c;Il! Taylor & Francis Group Boc. Raton London New York CRC Press is an imprint of the Taylor Ei Francis Group, an informa bUSiness Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by A.A.Balkema, Rotterdam, provided that the base fee ofUS$1.50 per copy, plus USSO.I0 per page is paid directly to Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, USA. For those organizations that have been granted a photocopy license by CCC, a separate system of payment has been arranged. The fee code for users of the Transactional Reporting Service is: 90 54106204/95 US$I.50 + US$O.I O. Published by A.A.Balkema, P.o.Box 1675,3000 BR Rotterdam, Netherlands (Fax: +31.10.4135947) A.A. Balkema Publishers, Old Post Road, Brookfield, VT 05036, USA (Fax: 802.276.3837) ISBN 90 54106204 © 1995 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business Contents Preface VIII 1 Introduction 1 2 Rock cutting theories 4 3 Possible wear mechanisms at the wear-flat of rock cutting tools 7 3.1 Introduction 7 3.2 Wear type classifications 8 3.2.1 The motion category classification 8 3.2.2 The wear mechanism classification 8 3.3 Wear mechanisms relevant to rock cutting tools 10 3.3.1 Abrasive wear 11 3.3.2 Adhesive wear 14 3.3.3 Sliding wear 16 3.3.4 Total wear due to sliding motion contact 16 4 Wear mode hypothesis 18 4.1 Introduction 18 4.2 Cutting forces 18 4.2.1 Influences of rock material properties on cutting forces 19 4.2.2 Influences of rock mass properties on cutting forces 19 4.2.3 The influence of some operating condition factors on cutting forces 19 4.3 Rock relief strength 20 4.3.1 The influence of rock material strengrn properties on relief strength 20 4.3.2 The influence of the geometry of the relief on relief strength 21 4.3.3 Hardness of the mineral grains 21 4.4 Wear mode prevalence 22 5 Rock cutting tests to study wear 26 5.1 Introduction 26 5.2 The scraping test 28 v VI Contents 6 Rock properties with respect to wear 34 6.1 Introduction 34 6.1.1 Rock property based rock cutting wear index values 34 6.1.2 Some considerations on the non-intrinsic rock property parameters 35 7 Experiments 40 7.1 Introduction 40 7.2 Scraping test experiments 40 8 Chisels used in the experiments 44 8.1 Introduction 44 8.2 Chisel material 44 8.3 Chisel shape 45 8.4 Thermocouple 46 9 Properties of rock types used in the experiments 48 9.1 Rock material properties 48 9.1.1 Interpretation of the measured and derived rock properties 49 9.2 Rock sample preparation 55 I0 Test results on artificial rock (mortar) 56 10.1 Repeatability and the effect of groove spacing 56 10.1.1 Effect of spacing of the grooves, sawn into the rock disc 56 10.1.2 Repeatability of the experiments, with respect to the amount of wear 56 10.2 Scraping test experiments on mortar at constant cutting velocity 57 10.2.1 Experiments on mortar composition 1 58 10.2.2 Results ofexperiments on three mortars of different strength 61 10.2.3 Results of experiments on four mortars of different grain size 13 10.2.4 Results ofexperiments on three mortars of different volume percentage of abrasive grains 78 10.2.5 Results of experiments on two mortars of different shape of the quartz grains 82 10.2.6 Results of experiments on mortars ofdifferent mineral content 84 10.3 Specific wear equations based upon scraping test experiments on mortar 87 10.4 Scraping test experiments on mortar with varying cutting velocity 89 10.4.1 Experiments on mortar composition 8 91 10.4.2 Experiments on different mortars 91 10.5 Comments on the experiments on artificial rock (mortar) 99 11 Test results on natural rock types 100 11.1 Introduction 100 Contents vn 11.2 Experimental results 100 11.2.1 Experiments on sandstones 100 11.2.2 Experiments on limestones 105 11.2.3 Co"elation of test results obtained in experiments on artificial or natural rock 105 11.3 Comments on the experiments on natural rock I09 12 Relation of the scraping tests with rock cutting projects in practice 110 12.1 Description of the T-850 rock cutting trencher 114 12.2 Calculation of the feed of a single bit of the T-850 rock cutting trencher 114 12.3 The specific wear in the schnarrtanne granite and the oberdorfer sandstone, predicted on the basis of results from the scraping test experiments 115 12.4 Comparison of the field results with the experimental results 117 13 Conclusions 121 14 Closing remarks and recommendations 124 Nomenclature 125 List of abbreviations and symbols 126 References 127 Appendix 1: Comparison of porosity values determined by different methods 132 Appendix II: Petrographic descripitions 133 Appendix Ill: Momentary cutting forces in tests on Elb-sandstone D 143 Preface The need to get a better understanding of the basic processes of wear in rock cutting has resulted into the study "Wear of Rock Cutting Tools". Two inter-related books were produced in close cooperation of the authors. The books highlight different aspects of the study and may be read standing alone as well as a couple. Both studies are mainly directed towards the effects of different rock types (and geological setting) on the processes of tool wear during rock cutting. "Laboratory Experiments on the Abrasivity of Rock" by Jan Reinout Deketh provides a better understanding of basic wear processes in laboratory rock cutting wear experiments, by which the site investigation for rock cutting projects like dredging, trenching and tunnelling may be tuned. "Site Investigation for Rock Dredging" by Peter Verhoef provides a general view over the wide range of aspects which are involved in engineering geological site investigation for rock dredging. At the time I started this work a lot of preliminary investigations were already carried out by and under the supervision of Peter Verhoef. Moreover also during my work into this subject I was supported by him and other people from the Section Engineering Geology at the Faculty of Mining and Petroleum Engineering of Delft University of Technology. I thank Peter Verhoef for all this and for giving me the opportunity to write this book. My dearest friend, Marina Giezen, supported me during the years and helped me completing this thesis. She contributed to this work directly by performing a study into the wear of bits of rock cutting trenchers. Her study of wear and production of rock cutting trenchers in different types of rock was essential by demonstrating the relevance of the laboratory experiments to a specific example of rock cutting in practice. Her work was made possible by Vermeer Manufacturing Company (Pella, Iowa, USA). This research has been sponsored by the Dutch Technology Foundation (STW Stichting Technische Wetenschappen). Jan Reinout Deketh, December 1994 VIII CHAPTER 1 Introduction In many civil engineering and mining projects the earth surface has to be remodelled, prepared or removed for the benefits and needs of a specific project. Such projects involve, for example, open pit or underground mines, tunnels, dredging works, trenches etc. Nowadays manpower is aided or replaced by blasting techniques and excavation machines like dredgers, trenchers, roadheaders, tunnel boring machines etc., which all have their specific advantages and applications. A common problem of most excavation machinery, based on mechanical action, is the unknown interaction of cutting tools with varying types of rock and geological settings. The development of more powerful machines and improved technology enables the cutting of increasingly stronger rock. Unexpected high rates of wear of the cutting tools and low production rates resulting in high financial losses and law-suits between contractors, clients and consultants may be the consequence. The financial losses can be so substantial that the existence of major dredging firms could be endangered. In the work by P.N.W.Verhoef (1995) some cases are discussed of dredging projects which had major problems with wear of the cutting chisels which had not been anticipated. A large number of investigations has been carried out to determine which factors are of influence to tool wear due to rock cutting. It seems, that wear problems are system dependent problems. Therefore studies about wear are only comparable when the wear system and conditions are more or less equal. Many studies look at a part of a wear problem and therefore only describe the factors which affect that part. Most factors that influence wear due to rock cutting can be placed into the following groups. 1.rock material properties (texture, strength, composition, hardness etc.) 2.rock mass properties (structure, inhomogeneities etc.) 3.type of machinery (type of tools, machine cutting principle etc.) 4.choice of machine settings (thrust, r.p.m. of the rotary cutting device etc.) 5.environment (submerged or dry, weather conditions, operator skills etc.) For example quartz grains are abrasive to cutting tools made of steel but are hardly abrasive to cutting tools made of tungsten carbide. This is the case at room temperature. If temperatures at the wear-flat of a cutting tool become as high as ± 800 °C, the hardness of tungsten carbide decreases and quartz (and possibly even softer minerals) becomes as abrasive to the tungsten carbide as to steel. High 1

See more

The list of books you might like

Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.