Blast induced ground vibration is one of the key concerns from safety view of nearby structures. There are many direct and indirect parameters responsible for blast induced ground vibration. Explosive parameters including its charging quantity and quality is one of them. Velocity of detonation of explosives, its interaction with rock strata and charging condition of a blasthole influences blast outputs in the form of fragmentation as well as undesirable effects like ground vibration, flyrock, air-over-pressure/noise etc. Researchers around the globe have established empirical formulations to investigate effects of explosive parameters on blast induced ground vibration. Following paper focused on investigating influence of charging parameters on blast induced ground vibration. Numerical simulation using dynamic modelling package of FLAC3D have been used for this. Signature hole geometry with rock properties and explosive properties in the form of detonation pressure has been modelled. Detonation pressure of the explosive was estimated from recorded in-the-hole velocity of detonation and density data for different explosive types. Damping parameters in the form of damping coefficient and frequency has been given to deplete blast vibration velocity for the medium. This was estimated by back calculation from recorded blast vibration data. Influence of hole diameter, distance of blast face from monitoring point, column length of explosive charge and charge distribution on blast induced vibration were assessed. Blast induced ground vibration in the form of history of velocity peaks has been plotted against dynamic time of blast wave propagation. Results of the dynamic simulation shows effects of hole diameter and charge column length on blast vibration in the same line with explosive weight per delay considered in USBM predictor equation. Investigation of effects of distance on blast induced vibration shows dependency of blast vibration on directional distance rather than radial distance. Charge distribution effects shows considerable reduction in blast vibration magnitude for distributed charge than full column charge.
Keywords: Peak particle velocity, peak vector sum, dynamic simulation, damping coefficient, blast induced vibration
In recent years, accidents due to slope failures in openpit/ surface mines have shown an upward trend. The major factor causing such failures is the lack of scientific design of the pit and the dump slopes in mines and therefore, an optimum design of slope angle vis-à-vis slope height is of paramount importance. The slope design process is an iterative one involving large amount of computation and voluminous data, making the process a tedious and time consuming one. However, application of computer can effectively minimize these difficulties provided that a suitable computer package is available for the purpose. A good number of software are available nowadays for slope stability analysis and/or design. However, most of these software are not suitable for automated design of new slopes. In this paper, a simplified algorithm for automated design of homogeneous slopes in open pit/surface mines using limit equilibrium method (LEM) has been proposed.
Keywords: Surface mine, algorithm, automated design, homogeneous slope, LEM
In the present paper, an acoustic emission trend in the Kaiser effect of rocks was studied and possibility of its application in the estimation of in-situ rock mass stress was explored. Several methods have been proposed for estimating in-situ stress in the laboratory from rock core samples collected from the boreholes. Among them, acoustic emission (AE) method based on Kaiser effect is the simplest. Conventionally, in-situ stress is estimated by plotting cumulative events versus stress. The change in the slope of the curve is an indicator of the Kaiser stress. In the present study, borehole drilled samples from five sites were investigated in the laboratory by AE method for which the in-situ stress was already measured by hydrofracturing method. A plot of cumulative events versus stress indicated three types of trend and is named as type 1, 2 and 3. It is easy to identify the Kaiser stress if the trend is of type 1. Types 2 and 3 trends do not show any perceptible change in the slope of the curve and it is impossible to identify the Kaiser stress. Since most of the samples showed type 2 and type 3 trend, to estimate the Kaiser stress, other AE parameters namely ring down count, energy and absolute energy of the events were used. Among these parameters, absolute energy plot showed more significant change in the slope, and hence preferred for identification of the Kaiser stress.Read more
The paper describes the application method of symmetrical components for the analysis of unbalanced mine power distribution systems using B2-Spice. The knowledge of symmetrical components is extremely useful for the study of unsymmetrical faults in three-phase power networks. The concept is also useful for studying the three-phase machine behaviour under unbalanced conditions. B2-Spice is a general-purpose analog electrical and electronic circuit simulator. It is a powerful programme that is used to study the integrity of circuit designs and to predict circuit behaviour.
Keywords: Mine distribution system; unbalanced faults; symmetrical components; sequence networks; B2-Spice circuit simulator
Efficiency and effectiveness of equipment play a dominant role in modern mining industry to determine the performance of mining equipment as well as mines. Greater the efficiency and effectiveness more productive is the organization (mine). As it is known that mining industry is a very capital intensive industry. Hence, a proper performance measurement is very necessary in this field. Since last many years, overall equipment effectiveness (OEE) has been used in different industries as a measure of performance, but due to limitations in the original OEE, it has been modified continuously time to time by different researchers and practitioners in the different field accordingly. Since, last two decades OEE has also been used in mining industry. This research assigns different weightage to different components by using analytical hierarchy process (AHP), and thereby determines the weighted OEE i.e., machine performance index (MPI). The main purpose of assigning the weightage is to show the influence of each component in the evaluation of OEE. In original OEE, the weightage given to each component was equal which was not justifiable logically. To check the applicability of this new method, a case study was done on dumper in an opencast coal mine of India.
Keywords: Dumper; OEE; Performance; weightage; AHP, MPI
Studies have been carried out for analyzing the flotation performance of chalcopyrite ore from Rakha mines, Jharkhand. The full factorial methodology has been used for design of experiments. The reagents (collector and frother) dosages and time were independent variables and recovery and grade has been considered as responses. The minimum and maximum values of operating conditions were chosen after performing preliminary experiments at different operating conditions. The effect of the variables (species interaction – main and interactional) on recovery and grade were studied. In this work, the experimental data were compared to data obtained from the factorial design of experiments to check the validation of model. The results obtained for bulk were analyzed to calculate the optimized condition for effective recovery and grade.
Keywords: Chalcopyrite ore, flotation, reagent, metallurgical performance, statistical analysis
Chemical and mineralogical characteristics of Panxi vanadium–titanium magnetite tailings are studied to beneficiate the contained ilmenite. A pilot study using a spiral chute to precocentrate the tailings, combined with table enrichment, is carried out. The aluminosilicate content of the tailings is high and the TiO2 content is only 10.28%. Titanium mainly existed in the form of ilmenite and titanomagnetite, which accounted for 78.02% of total titanium. Although most ilmenite is dissociated, a small amount is embedded in the gangue. More than 90% of the gangue comprised titanaugite, plagioclase, and serpentine. After sorting the sample by spiral chute, a large amount of gangue is discarded and a coarse concentrate with a TiO2 grade of 23.54% is obtained. This is enriched using a table to obtain a final concentrate of 36.85% TiO2 with an overall recovery of 71.75%. Titanium pre-enrichment is achieved.
Keywords: Vanadium-titanium magnetite; process mineralogy; embedding characteristics; preconcentration; gravity beneficiation
Detailed mineralogical and geochemical studies are carried out on iron ore tailings from Donimalai iron ore deposits (DIOD), India. The mineralogical studies using X-ray powder diffraction on the tailing samples shows the presence of major iron (Fe) bearing phase hematite (Fe2O3) and the gangue minerals such as alumina and silica are present in the form of kaolinite (Al2Si2O5(OH)4) and gibbsite (Al(OH)3). The geochemical study of the tailings shows the assay amount up to 56.32% Fe, 9.35% SiO2, 5.82% Al2O3, 0.057% P and 2.60% loss on ignition (LOI). An elaborate study on the tailings was carried out with the help of DLS (diffraction light scattering system), SEM-EDS (scanning electron microscope-energy dispersive spectroscopic analysis) which shows that most of the slime particles lie below the range of 150m to 70m, only less number of fractions are found in the lesser micron size. Moreover, tailing contains Fe (iron) bearing hematite with interlocking gangue minerals. The detailed liberation analysis of the tailings shows the major iron-bearing phase has been present in coarser size and more gangue minerals are present in the finer fractions. Beneficiation is carried out for the tailings using hydrocyclone. Based on selection of different process parameters such as spigot diameter (mm), vortex finder diameter (mm), pressure (psi), and solid concentration (%) the beneficiation is performed. Beneficiation through hydrocyclone increases the Fe content from 56.32 to 62.04% with a solid recovery rate of 32%, which can be utilized for blast furnace operation.
Keywords: Donimalai, tailing, XRD (X-ray powder diffraction), SEM-EDS (scanning electron microscopeenergy dispersive spectroscopy), DLS (dynamic light scattering), hydrocyclone