Master of Science in Mining and Mineral Exploration

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    item: Thesis-Full-text
    Effectiveness of emulsion explosives in quarrying in high grade metamorphic rocks in Sri Lanka
    (2017-06) Pathirana, KPR; Weerawarnakula, S; Hemalal, PVA
    In mining, blasting is the predominant method adopted for breaking consolidated rocks with the main objectives being extraction of minerals at minimum cost with minimum damage to the environment. Explosive is a compound or a mixture of compound which is capable of undergoing extremely rapid decomposition with deflagration or detonation. When the explosive reaction takes place radial cracks are form by as a result of detonation pressure with fragmentations followed by gas pressure. The optimization of explosive usage in Sri Lankan metamorphic rock is the main objective of this research. The detonation velocity of the explosive should match, as closely as possible, the sonic velocity of the rock to be blasted of rock. The rock's sonic velocity is a reliable indicator of its structural integrity and resistance to fragmentation. With varying rock types, sonic velocities vary with varying structural formations. Aggregate impact value is one parameter of hardness of rock. This study is conducted by considering the aggregate impact value as the indicator of hardness of rock. Test is planned, keeping blasting parameters constant namely hole diameter, explosives charge, burden, spacing and stemming against the different rock types with different aggregate impact values. The efficient use of explosives, along with the proper selection, will be the key to a successful blasting program. After comparison of the results of production rock volume and fragmentation formulate the explosives usage to get the optimum results that how explosives behave with the different rock types with different aggregate impact values or hardness. Dautrich method is the first time practically used in Sri Lankan field to determine the velocity of detonation of emulsion explosives in this research. This method is indirect field test method for suggesting VOD of explosives and the determination of the VOD is based on the fact that processes that propagate at different linear velocities travel different distance, in the same time interval. According to the blast results harder rocks fragmented with emulsion explosives, higher production volume were obtained than less hardness rocks. Increasing the hardness, increasing the production rock volume. Therefore, the relationship with hardness of rock and emulsion explosives usage is observed. Fly rock throw is more important to safety of blasting. This research indicates that fly rock distance is higher with AIV values more than 27. This result clearly indicates that emulsion explosives is very suitable for Sri Lankan metamorphic hard rocks.
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    item: Thesis-Full-text
    Effect of trenching on blast-induced ground vibration in sri lankan metal quarries
    Samarakkody, SATI; Dharmarathne, PGR; Premasiri, HMR
    Problems due to ground vibration are a matter of serious concern for the users of explosives. It is not possible to eliminate vibration completely or to contain them at the source. Effort need to be made in controlling them within safe level, without effecting the production schedules and economic viability of the project. When predicted or monitored vibration exceeded the statutory limit, ground vibrations are generally controlled by modifying the blast design parameters. In critical situation, digging a trench has reduced ground vibration. The extent to which it can reduce ground vibration has been examined by field experiments at a open cast quarry mine located at Arankele in Sri Lanka. After selecting a suitable quarry site at Arankale off Kurunagala in North-Western province of Sri Lanka. Suitable place for blasting face, digging a trench and observation point have been identified. Vibration measurement were carried out after single shot hole blasting method prior to digging a trench and after digging the trench with variation of depth of drill holes and depth ofthe trench, at points located just before the trench(A), just after the trench (B) and approximate observation point away from the trench (C). Average often single shot hole blast carried prior to digging trench show ground vibration reduction percentage are 6.326% ,1.23%, 7.023% and 18.309% at B, and 72.262%, 54.474%, 55.183%, and 45.191% at C. Results after digging the trench show ground vibration reduction percentages are 57.878%, 53.946%, 40.514% and 36.757% at B and 55.509%, 64.787%, 56.848% and 42.382% at C. Such results indicate, just after the dug trench, ground vibration reduction level is very much higher compared to the results obtained before digging the trench. However considerable deferences have not been observed at the observation point under same condition. The results also show that the percentage of the reduction depend on the trench depth to blast hole depth ratio.
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    item: Thesis-Full-text
    Comparative study of emulsion and water gel explosives for rock quarrying
    Herath, B; Hemalal, VPA; Dhramarathna, PGR; Rohitha, LPS
    In the mining field, blasting is the predominant method for breaking of consolidated rocks and the main objectives are to extract the large quantity at both minimum cost and having minimum damage to the environment. Rock breaking , over the years , which was limited to just breaking of boulders for the use of building and road construction has developed vastly to various aspects of mining namely ,open cast, underground and underwater blasting. Manually drilled single shot bore holes are disappearing and making way to multiple bore holes of immense depth with the introduction of the latest blasting technologies. Result of the introduction of optimum blasting techniques and sustainable development criteria, mining industry has twisted in the path of eco-friendly mining. Explosives and blasting techniques that are used nowadays are based on the above concept. Use of Dynamite changed to lesser powerful explosives such as Water Gel and then to Emulsion explosives. Our country also discarded the use of Dynamite several years ago and Water Gel explosives was introduced. Water Gel explosives is eco friendlier than Dynamite but could not be substituted in areas underground and underwater blasting. Introduction of Emulsion explosives was mainly to overcome these disadvantages of Water Gel Explosives. Aim of this study is to carry out a comparative study in all areas of open cast mining and to ascertain the most appropriate high explosive type for optimum output.
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    item: Thesis-Full-text
    Relationship between los angeles abrasion value and mineralogy of rocks
    Dayarathna, IWTP; Puawawala, UGA; Rohitha, LPS; Abeysinghe, AMKB
    This research includes study of the relationship between Los Angeles Abrasion Value and the mineralogy of rock aggregates narrowed down to the commonly found high grade metamorphic rocks in Sabaragamuwa Province. The study was carried out minimizing the effect of other factors as much as possible. Los Angeles Abrasion Test and Mineral content of each rock sample selected was determined at the laboratory. Thin section analysis was carried out to determine the mineral content with the help of electronic microscope equipped with a digital camera and the AutoCAD software. Most of the rock quarries in the study area consist of biotite gneisses. Two samples are selected to represent them. Most of the other samples were selected from waste rock piles of quarries to have samples with varying content of minerals.The Regression Analysis was carried out to develop a relationship between Los Angeles Abrasion Value with engineering and mineralogical properties such as Relative Dry Density, Quartz Content, Feldspar Content as well as Mica Content. The best regression line fit for the test results is a third order polynomial line between Quartz Content and Los Angeles Abrasion Value which shows coefficient of determination as 0.7952. Another important achievement of this study was developing a field guide to assist the personnel at the field work. It was completed with the photograph of each rock sample , microscopic view of the sample and their respective engineering and mineralogical properties such as Los Angeles Abrasion Value, Dry Density, Quartz Content, Feldspar Content and Mica Content.
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    Influence of mechanical and aggregate properties of rock on powder factor in rock blasting
    Karunanayake, KDP; Dharmaratne, PGR; Rohitha, LPS
    Quarry metal is a widely used material in any large scale construction industry. Though demand for quarry metal substantially increased due to recently emerged large infrastructure development projects in Sri Lanka such as highway and port city, profit margins of the quarrying has drastically reduced due to high powder factors recorded in recent rock blasting activities of local quarries. Most possible reason for realizing high powder factors could be the introduction of various new explosive agents such as water-gel in to the local mining industry. Importance of analysing the influence of mechanical and aggregate rock properties on powder factor arises in this context to allow seeking suitable rocks those incur minimum blasting expenditure during the production stage. Outcomes of the project can be used to predict powder factor which could be achieved in blasting operations of a certain rock even before starting the quarry operations to minimize its production cost in the long run. Eight quarries operates under the close supervision of qualified Mining Engineers were selected for this study to ensure blasting geometry and configurations have being properly managed during the realized powder factor data recorded time period. Random core samples were obtained from each quarry site and they were tested for Density, Uniaxial Compressive Strength (UCS) and Tensile Strength. Similarly, random aggregate samples were taken and performed the Aggregate Impact Value (AIV) test. Rock Mass Rating (RMR) was determined for each quarry using UCS values and other field data obtained at the site. Explosive consumption and drilling records for recent six month were obtained from each quarry for the calculation of powder factor. Powder factor was plotted against each selected rock property and regression analysis was performed on test results to understand their standalone influence. The only realized best fitting model for the Powder Factor was AIV according to the regression analysis and it is very closely following the quadratic model. Rock property test results and past records of few other quarries were used to validate formulae obtained in this research. Explosive cost and production cost of all the quarries analysed for the same six months period. Results revealed that the production cost is a function of explosive cost since other costs on drilling, machineries and labour are usually incur relatively fixed costs in nature. Hence it can be concluded that the aggregate rock properties, especially Aggregate Impact Value (AIV) influence on powder factor of blasting and furthermore affects economics of the quarry production. More importantly, combined formula derived in this research can be used predicting powder factor of a fresh rock before conducting any blasting activity.