Characterisation of hydrogen peroxide based explosives and ventilation modelling to quantify re-entry times in underground development blasting Virginia Bailey BEng (Mining) A thesis submitted for the degree of Master of Philosophy at The University of Queensland in 2017 School of Mining and Mechanical Engineering Abstract Cartridge products have been used in underground applications since the development of dynamites from nitro-glycerine. Their ease of use, in both large and small quantities, make them ideal for use in underground development mining. However, the amount of gases produced by early day cartridge products proved to have safety and operational limitations. Formulation improvements have reduced the risk of premature detonation due to sensitivity, yet the presence of toxic nitrous oxides (NOx) and carbon monoxide (CO) gases still remain as nitrates continue to be used in the formulation. The levels of NOx and CO gases produced have a marked effect on the length of time taken to re-enter underground mines following blasting activities. The non-producing time when the toxic blast gases are clearing from the underground environment is known as re-entry time. Utilising an explosive product which has a nitrate free oxidiser, and/or a carbon free sensitiser has the potential to reduce the production of toxic gases, and therefore decrease the time required for these gases to clear to enable safe entry to the mine for personnel. Reducing non-production time directly leads to an increase in available time for active work per shift, thus contributing to rapid development. The mining industry consistently desires a positive step-change in development practices to enable faster and safer access to underground deposits; and thus achieve ramp-up production much earlier than is currently possible. The objective of this research is to evaluate and better understand the potential application of innovative explosives (NOx free and reduced CO) to minimise or eliminate re-entry times which can support rapid development practices. Key tasks to achieve this objective included developing an alternative explosive characterisation program coupled with ventilation modelling analysis through improved algorithms. As part of the characterisation program, a total of twenty-six (26) unconfined tests were completed in order to characterise the performance of newly-developed explosives. Of the 26 test samples, seven failed to complete full detonation of the charge column. Seventeen (17) different product formulations were tested. All 26 test samples had critical diameters which ranged from 20 mm to 25 mm for products sensitised with gas to 0.49 g/ml and 0.9 g/ml. Non-ideal detonation behaviour was exhibited by all products tested, in that the velocity of detonation (VOD) was influenced by the density and the charge diameter. Detonation velocities ranged from 1,950 m/s up to 3,950 m/s for varying densities and diameters. High speed camera technology was also used to study the detonation process, producing images and information not previously available to industry. i Another important component of this thesis was to model and quantify the potential benefits of NOx and CO reductions from these new explosives at an operational level. In order to achieve this, ventilation modelling using an improved algorithm was conducted. Simulations included a relative comparison of a typical ammonium nitrate emulsion product and the newly developed peroxide based alternative explosive. This work is the first time this type of relative comparison is conducted with a widely used and accepted ventilation modelling package. Through this desktop study, the author was able to identify some deficiencies in the embedded algorithms which led to the development of improved algorithms. In this work, three different ventilation models were run to evaluate the impact on re-entry times due to contaminant dispersion rates in single and multiple headings. Models were based on a working underground mine in Southern Africa, with known re-entry times from time studies conducted at varying stages of development. Data from this particular operation was used to calibrate the model. Overall results showed that with the use of an alternative hydrogen peroxide (HP) based explosive there is an average potential reduction in re-entry times of 13% for both single heading and multi-heading operations. The total carbon monoxide concentrations through the use of HP alternative cartridge explosive products is reduced on average by 50% compared to a typical AN based underground emulsion product. The total nitrous oxide concentrations are eliminated. Further optimization work that accounted for the possibility of reducing the number of blast holes in a face due to the higher available energy per weight of the HP product when compared to the AN emulsion, showed further improvements to re- entry time. Re-entry times decreased by 27% and 32% in single heading and multi-heading operations respectively, with a 62% reduction in carbon monoxide. The findings from this modelling work are unique and significant because any reduction in re-entry time can result in an increase in available production time. For an active underground mine, this translates into an effective thirty three (33) additional 12 hour shifts of work becoming available per annum in a single heading operation; or twenty-eight (28) additional shifts becoming available in a multi-heading operation. As discussed earlier, this can enable faster and safer access to underground deposits allowing ramp-up production to be reached much earlier having a direct positive impact on Net Present Value. ii Declaration by Author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, financial support and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my higher degree by research candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis and have sought permission from co- authors for any jointly authored works included in the thesis. iii Publications during candidature No publications Publications included in this thesis No publications included iv Contributions by others to the thesis Significant and substantial inputs made by others to the research, work and writing represented and/or reported in the thesis included: Dr. Italo Onederra for input into the conception and design of the thesis project and critical revision of draft thesis reports. Miguel Araos significantly contributed to the design of the unconfined surface tests, which included development and mixture of all chemical formulations. Statement of parts of the thesis submitted to qualify for the award of another degree None Research Involving Human or Animal Subjects No animal or human subjects were involved in this research. v ACKNOWLEDGEMENTS The author wishes to thank the following people for their support throughout this thesis: Dr. Italo Onederra, for his advice and guidance throughout the entire project. From go to woe, this thesis would not have been possible without his help, input and persistent pushing. Mr. Miguel Araos, for his vision of HP product and his drive and determination in setting field trials. I wouldn’t begin to grasp the chemistry behind this project without his mentoring. Mr. Lee Hayter from Extech, for providing his skills and expertise in blasting to enable safe and efficient blasting trials. The team at VentSim for willingly providing me with a full access educational licence to complete ventilation simulation modelling remotely from University of Queensland. Massive thanks for promptly answering my algorithm queries and assisting with revisions. All the shift supervisors, Project Managers, Project Engineers and Operational Managers from McMahons, Byrnecut Offshore, Barminco, AUMS, Murray & Roberts and Downer EDI who participated in the Industry survey and provided valuable time study and design data. The amount of support and continued feedback throughout this project has been amazing and words cannot describe how appreciative I am. vi Financial support This research was partially supported by a CRC Mining Living Allowance Scholarship vii Keywords alternative explosives, cartridge explosives, hydrogen peroxide explosives, rapid development, underground development mining, nitrous oxide fume free explosives Australian and New Zealand Standard Research Classifications (ANZSRC) ANZSRC code: 091405, Mining Engineering, 100% Fields of Research (FoR) Classification FoR code: 0914, Resources Engineering and Extractive Metallurgy, 100% viii TABLE OF CONTENTS ABSTRACT I DECLARATION BY AUTHOR III ACKNOWLEDGEMENTS VI CHAPTER 1 - INTRODUCTION 1 1.1. BACKGROUND 2 1.2. RAPID DEVELOPMENT 4 1.3. DRILL AND BLAST TECHNOLOGY FOR RAPID DEVELOPMENT APPLICATIONS 7 1.4. CURRENT RE-ENTRY INDUSTRY PRACTICES 9 1.5. ALTERNATIVE EXPLOSIVES AND THEIR POTENTIAL VALUE 15 1.6. RESEARCH MOTIVATION 17 1.7. RESEARCH OBJECTIVE 18 1.8.