Ground vibration generated by hydraulic rock breakers and its impact on the safety of nearby earthfill dam in a graphite mine

A detailed impact analysis on the effects of non-explosive chemicals and hydraulic rock breakers at a graphite mine in India close to an irrigation dam was carried out in this study. The dam was 70 m from the mining lease boundary. When a single hydraulic rock breaker worked on fractured rock mass, the magnitude of ground vibration recorded at 10 m on the same working bench was 2.37 mm s−1 but when it worked on fresh rock surface the ground vibration at 9 m on the same working bench was 4.67 mm s−1. Beyond 35 m on the same bench, no ground vibrations were recorded. Ground vibrations generated by three jack hammer drilling machines operating simultaneously on the same working bench were less than 0.5 mm s−1 when measured at 7.2 m distance. The combined effect on the magnitudes of ground vibrations by two hydraulic rock breakers operating simultaneously on the same bench 6 m apart was found to be negligible. The ground vibrations generated by hydraulic rock breakers and other mining activities were found to be lower than required to cause any structural damage or threat to the stability of the dam

Effect of layer thickness of rocks on blast fragmentation - case study in a limestone mine

The paper discusses the influence of layer thickness of limestone beds on blast fragmentation in different blasting benches of Aditya Limestone Mines of UltraTech Cements Limited. Blast fragmentation analysis was carried out using photographic method to determine the mean fragment sizes. Good correlations were obtained between average layer thicknesses and blast fragment size, power factor (t/kg) and charge factor (kg/m3). Mean fragment sizes less than 100 cm were obtained with the average layer thickness of limestone beds less than 80 cm. the powder factor more than 14 t/kg was achieved with layer thickness less than 200 cm. however, in geologically disturbed limestone strata, blast design patterns and joint parameters had significance in achieving desired fragment size

Study on the Trend of Accidents due to explosives in Indian Mining Industry and the Future Challenges

The cases of accidents in indian coal and non-coal mines during 2001-2009 were studied and analysed from the various available annual reports and standard notes. The study reveals that there is an overall decrease in number of accidents due to usage of explosives in the mines. The number of accidents due to use of explosive in indian mines was 15 in 2001 which has been reduced to 8 in 2009. Based on analysis of the trend lines plotted for fatal and serious accidents during the period it is clear that these declining trends are insignificant and not encouraging. The slope of the trend line for decrease in fatal accidents in non-coal mines is 8.280 whereas for coal mines, it is 6.200 only. The various challenges for future and need of the hour to mitigate the accidents due to explosives usage in mine s have been discussed and presented in this paper

An Investigation to Assess the Cause of Accident due to Flyrockin an Opencast Coal Mine: A Case Study

Abstract The paper deals with the investigation carried out to find out the possible reason of the fly rock incident causing fatality of one person at Bhurkunda ‘A´’ Colliery of Central Coalfields Limited (CCL). The flying fragment travelled up to 280 m from the blasting source causing the accidental death. The blasts were conducted in over burden rock strata consisting of medium grained sandstone and shale. The blast hole diameter used in the blast was160 mm, and the average hole depth was 6.0 m. Site mixed emulsion (SME) explosive was used in the blast, and explosive charge per hole was 50.00 kg. Non-electric initiation systems were used for in-hole explosive and surface hole-to-hole initiations. The design parameters used in the blast were thoroughly analyzed using blast simulation software to check any anomaly in the blast design viz. sequence of hole firing, success rate of burden movement, maximum charge per delay fired within 8ms windows, etc. The different fly rock fragments prediction models were used to assess the maximum possible travel distance of the flying in the blast. A synonymous blast was also conducted in the mines to replicate the blast where fly rock accident occurred. All the blasting events were recorded and monitored using a digital video camera. The simulation results of the blast showed the success rate of burden relief more than 80% with sufficient delay intervals for the rock movement during the blast. The maximum possible travel distance of flying fragments based on different fly rock prediction models was 227 m. In the synonymous blast only vertical throws of the flying fragments up to 70 m(approximate) height were observed. It was difficult to find out the exact cause of fly rock incident. However, based on the detailed investigation, it was concluded that the possible cause of flying fragments travelling up to a distance of280 m could be due to the presence of a weak zone in the rock strat

Numerical simulation of aluminum bar casting for wire rod production

913-918In a continuous casting of wire rod production, a cast bar, which is formed in a rotating wheel mould, is subsequently rolled by a set of rolls to form wire rod. Temperature of cast bar predicted by model has been verified by actual temperature measurement during casting at different operating conditions. Simulation results show the influence of various operating parameters on temperature distribution of cast bar

Synthesis, structure, and properties of mesoporous B/C/N microspheres

Reaction of low surface area carbon with a mixture of urea and boric acid at 930&#176;C yields a composition close to BC<SUB>4</SUB>N with a graphitic structure. BC<SUB>4</SUB>N was characterized by electron energy loss spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction. BC<SUB>4</SUB>N is a porous ceramic with a surface area of 428 m<SUP>2</SUP>&#183;g<SUP>&#8722;1</SUP>, and shows a CO<SUB>2</SUB> uptake of 40 wt-%. The layered structure of BC<SUB>4</SUB>N involves a random distribution of boron, carbon, and nitrogen atoms and shows high thermal stability up to 1000&#176;C. A comparative analysis of the structure and properties of BC<SUB>4</SUB>N and graphene using first-principles pseudopotential based density functional theoretical calculations is presented. The calculations predict it to be an insulator. The bulk modulus of BC<SUB>4</SUB>N exhibits an interesting dependence on the ordering of boron and nitrogen on the graphene lattice

BCN: a graphene analogue with remarkable adsorptive properties

A new analogue of graphene containing boron, carbon and nitrogen (BCN) has been obtained by the reaction of high-surface-area activated charcoal with a mixture of boric acid and urea at 900°C. X-ray photoelectron spectroscopy and electron energy-loss spectroscopy reveal the composition to be close to BCN. The X-ray diffraction pattern, high-resolution electron microscopy images and Raman spectrum indicate the presence of graphite-type layers with low sheet-to-sheet registry. Atomic force microscopy reveals the sample to consist of two to three layers of BCN, as in a few-layer graphene. BCN exhibits more electrical resistivity than graphene, but weaker magnetic features. BCN exhibits a surface area of 2911 m<SUP>2</SUP> g<SUP>−1</SUP>, which is the highest value known for a B<SUB>x</SUB>C<SUB>y</SUB>N<SUB>z</SUB> composition. It exhibits high propensity for adsorbing CO<SUB>2</SUB> (≈100 wt %) at 195 K and a hydrogen uptake of 2.6 wt % at 77 K. A first-principles pseudopotential-based DFT study shows the stable structure to consist of BN<SUB>3</SUB> and NB<SUB>3</SUB> motifs. The calculations also suggest the strongest CO<SUB>2</SUB> adsorption to occur with a binding energy of 3.7 kJ mol<SUP>−1</SUP> compared with 2.0 kJ mol<SUP>−1</SUP> on graphene

Chemical storage of hydrogen in few-layer graphene

Birch reduction of few-layer graphene samples gives rise to hydrogenated samples containing up to 5 wt % of hydrogen. Spectroscopic studies reveal the presence of sp3 C-H bonds in the hydrogenated graphenes. They, however, decompose readily on heating to 500 °C or on irradiation with UV or laser radiation releasing all the hydrogen, thereby demonstrating the possible use of few-layer graphene for chemical storage of hydrogen. First-principles calculations throw light on the mechanism of dehydrogenation that appears to involve a significant reconstruction and relaxation of the lattice