Faculty Publications

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    Gallery monitoring in blasting gallery panel during depillaring - A case study
    (2013) Kumar Reddy, S.; Sastry, V.R.
    About 50% of coal reserves in India are in seams thicker than 4.5m, which come under the category of thick seams, the exploitation of which is consistently posing challenges to the mining engineers. Extraction of thick seams by conventional hand section method is neither productive nor effective from the conservation point of view. The percentage of extraction by hand section mining in thick seams is as low as 25-30%. Sand stowing for working of thick seams cannot be considered as an option because the cost is prohibitive. Sand has become an increasingly scarce commodity along with timber. Blasting gallery (BG) method of depillaring thick coal seam is one of the productive methods with high production, productivity, economic and conservation. In this method, stability of workings and easily cavability of goaf is very important for safely extraction of pillars, safety of men and machinery. In this paper, strata monitoring data of load cells in galleries of a blasting gallery panel, where spoiling in pillars, instability of galleries and displacement of supports are monitored and analyzed during depillaring in specific geo-mining and working conditions of a underground mine in southern part of India.
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    Effect of width of gallery of highwall mining on stability of highwall: A numerical modelling approach
    (Inderscience Enterprises Ltd., 2014) Ram Chandar, K.R.; Kumar, B.G.
    Owing to continuous increased demand for coal, along with existing mining methods, some novel methods are being looked for. Highwall mining is such a method where considerable quantity of coal blocked in the highwall can be extracted to a great extent. The major challenge in highwall mining is roof control along with the stability of highwall. This method was introduced in one of the opencast coal mines first time in India. A systematic study was taken up using numerical modelling approach to assess the influence of width of gallery of highwall on stability of highwall based on field investigations. The width of gallery was taken as 3.5, 4.25 and 5.0 m. It was found that the stress and strain was more in case of 5.0 m wide gallery compared with 3.5 m wide gallery and the stress and strain values were more at the end point of galleries compared with the starting points of the galleries. The factor of safety values were decreased as the width of gallery increased from 3.5 m to 5.0 m. © 2014 Inderscience Enterprises Ltd.
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    Experimental study for the assessment of suitability for vegetation growth on coal mine overburden
    (Inderscience Enterprises Ltd., 2015) Ram Chandar, K.R.; Chaitanya, V.; Raghunandan, M.E.
    Owing to increased production and productivity of opencast coal mines, large amount of waste rock is removed and stacked in the form of waste dumps. Positive utilisation of such waste rock not only saves considerable dumping land but also reduces problem of maintaining stable and environmentally friendly dumps. One of the major utilisation of waste rock is to use it for vegetation. Therefore a systematic investigation to study the fertile characteristics of overburden waste rock for vegetation was conducted. Waste rock samples collected from an opencast coal mine dump in South India were used in the laboratory experiments. Observations showed the suitability of mine wastes for vegetation when supplemented with additives/nutrients - bottom ash, fly ash, lime stone powder and secondary sludge from sewage treatment plants (STPs) were considered for this purpose as additives. Results suggest that the mine-overburden supplemented with sewage waste (atleast 25% by volume) to be suitable for effective vegetation. © © 2015 Inderscience Enterprises Ltd.
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    Classification of Stability of Highwall During Highwall Mining: A Statistical Adaptive Learning Approach
    (Kluwer Academic Publishers, 2015) Ram Chandar, K.; Hegde, C.; Yellishetty, M.; Gowtham Kumar, B.
    The depleting coal deposits day by day required the introduction of novel methods of mining like highwall mining. Highwall mining is a method of extraction of coal blocked in the highwall. The method involves considerable challenges in the area of roof control and most importantly the stability of the highwall itself. Highwall mining has gained considerable importance all over the world, owing to the fact that the coal otherwise would not be extracted forever. This paper aims to assess the influence of varying conditions which can affect the stability of the highwall during highwall mining. The effect of gallery length, width of pillar and number of galleries are systematically studied through field investigations where a highwall mining was adopted first time in India. Initially, assessment was carried out using a numerical modelling approach and then the stability of the highwall is classified using multilinear regression, logistic regression and naive Bayes classifier. This will provide a mechanism to predict the stability of the highwall in future cases of similar conditions. The classification is done using statistical adaptive learning methods and a comparison of the methods is done. © 2014, Springer International Publishing Switzerland.
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    Miners’ return to work following injuries in coal mines; Powrót do pracy górników poszkodowanych w wypadkach w kopalni w?gla
    (Nofer Institute of Occupational Medicine ul. sw. Teresy od Dzieciatka Jezus 8 Lodz 91-348, 2016) Bhattacherjee, A.; Kunar, B.M.
    Background: The occupational injuries in mines are common and result in severe socio-economical consequences. Earlier studies have revealed the role of multiple factors such as demographic factors, behavioral factors, health-related factors, working environ­ment, and working conditions for mine injuries. However, there is a dearth of information about the role of some of these factors in delayed return to work (RTW) following a miner’s injury. These factors may likely include personal characteristics of injured persons and his or her family, the injured person’s social and economic status, and job characteristics. This study was conducted to assess the role of some of these factors for the return to work following coal miners’ injuries. Material and Methods: A study was conducted for 109 injured workers from an underground coal mine in the years 2000-2009. A questionnaire, which was com­pleted by the personnel interviews, included among others age, height, weight, seniority, alcohol consumption, sleeping duration, presence of diseases, job stress, job satisfaction, and injury type. The data was analyzed using the Kaplan-Meier estimates and the Cox proportional hazard model. Results: According to Kaplan-Meier estimate it was revealed that a lower number of dependents, longer sleep duration, no job stress, no disease, no alcohol addiction, and higher monthly income have a great impact on early return to work after injury. The Cox regression analysis revealed that the significant risk factors which influenced miners’ return to work included presence of disease, job satisfaction and injury type. Conclusions: The mine management should pay attention to significant risk factors for injuries in order to develop effective preventive measures. © 2016, Nofer Institute of Occupational Medicine. All rights reserved.
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    Primary Fragmentation Behavior of Indian Coals and Biomass during Chemical Looping Combustion
    (American Chemical Society service@acs.org, 2018) Pragadeesh, K.S.; Ruben Sudhakar, D.R.
    Devolatilization and fragmentation are important physical phenomena occurring during solid fuel chemical looping combustion (CLC). Primary fragmentation during devolatilization strongly affects the rate of fuel conversion, emissions, and fine particulates generation in a fuel reactor of a fluidized bed CLC unit, thus forming a critical design input. The present study focuses on investigating the primary fragmentation behavior of large coal and biomass (wood) particles during the devolatilization phase of CLC. Three types of coals (two Indian coals, one Indonesian coal) and one type of Casuarina wood of three sizes in the range of 8-25 mm, at different fuel reactor bed temperatures (800, 875, and 950 °C) are studied for primary fragmentation. Iron ore with 64% Fe is used as the oxygen carrier bed material, with steam as the fluidizing medium in the fuel reactor. The fragmentation behavior is expressed in terms of the number of fragments, fragmentation index, frequency of fragmentation, and particle size distribution of fragments at different residence times of coal during devolatilization in the fuel reactor. Under the conditions of study, the number of fragments increases with an increase in particle size and temperature, for all fuels studied. Also, it is found that the number of fragments increases with the decrease in compressive strength of both coal and biomass particles. The Indian coals are found to fragment in the earlier stages of devolatilization, while the Indonesian coal and the biomass particles begin to fragment in the later stages of devolatilization. The maximum fragmentation index is found with Indian coal - IC1, which has the highest fixed carbon content among the fuels studied, and the least value is observed in biomass. Different modes of fragmentation exhibited by each fuel type is discussed. Indian coals do not show any volumetric changes as such, whereas Indonesian coal indicates some degree of volumetric expansion. © 2018 American Chemical Society.
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    Color Indistinction Method for the Determination of Devolatilization Time of Large Fuel Particles in Chemical Looping Combustion
    (American Chemical Society service@acs.org, 2019) Pragadeesh, K.S.; Ruben Sudhakar, D.R.
    Chemical looping combustion (CLC) is one of the promising fuel conversion technologies for carbon capture with low energy penalty. Devolatilization is an important physical phenomenon occurring during solid fuel CLC. Devolatilization behavior influences fragmentation, combustion rate, emission, and particulates generation in fluidized bed CLC (FB-CLC), thus a critical input for its design. Existing visual techniques for determining devolatilization time cannot be applied in CLC conditions because of its flameless combustion nature. In the present study, a new, simple, and quick technique called "color indistinction method" (CIM) is proposed for the determination of devolatilization time (?d) in FB-CLC, where the end of devolatilization is inferred from the disappearance of fuel particle in a hot fluidized bed. Single-particle devolatilization studies in FB-CLC are conducted to determine the devolatilization time using CIM for two types of fuels, viz., coal and biomass (Casuarina equisetifolia wood), of size range 8-25 and 10-20 mm, respectively, at three different fuel reactor bed temperatures (800, 875, and 950 °C) and one fluidization velocity. The proposed technique is validated in three ways: (i) the measurement of residual volatiles present in char by thermogravimetric analysis; (ii) mass loss history of the fuel during devolatilization; and (iii) diagnostics using particle center temperature measurements. The results of CIM experiments, in terms of degree of error involved, are compared with an established flame extinction technique (FET) and a more accurate particle center temperature (PCT) method. The amount of volatiles released during devolatilization, as determined by CIM, is 91.3% for coal and 98.9% for biomass. These values compare very well with the results of the established FET, in which the volatile release is 90.7% for coal and 99.1% for biomass samples. The devolatilization times determined using CIM are in line with particle center temperature measurements with an acceptable error range of -7.57 to +3.70%. The proposed CIM is successful in establishing the devolatilization time of different fuels in CLC conditions and can also be applied in other flameless combustion conditions. © 2019 American Chemical Society.
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    Musculoskeletal Disorders Among Dozer Operators Exposed to Whole-Body Vibration in Indian Surface Coal Mines
    (Springer, 2020) Jeripotula, S.K.; Mangalpady, A.; Raj, G.R.
    Dozer operators are frequently exposed to whole-body vibration (WBV) during the execution of their work. Occupational exposure to WBV in Indian surface coal mines was evaluated by measuring vibration intensity and duration of exposure. A triaxial accelerometer was placed on the operator seat surface for taking the readings. Based on frequency-weighted root mean square acceleration equivalent to 8-hr shift duration, i.e., (A(8)) all dozer operators have exceeded an Exposure Action Value (EAV) of 0.5 m/s2, and 90% of dozers did not exceed Exposure Limit Value (ELV) of 1.15 m/s2. Based on Vibration Dose Value (VDV (8)), all dozer operators have exceeded Exposure Limit Value (EAV) of 9.1 m/s1.75, but no dozer operators have exceeded Exposure Limit Value (ELV) of 21 m/s1.75. Further, an epidemiological study was performed for identifying the extent of musculoskeletal disorders (MSDs) among dozer operators. For the detailed study, 42 dozer operators and 22 controls were selected from 2 surface coal mines. The control group was not exposed to WBV. It was seen from the cross-sectional study that pain in the lower back was predominantly higher (83.33%) in the exposed group when compared with the control group (31.81%). Likewise, pain in the neck (47.61%), shoulder (42.85%), knees (42.85%), and ankle (11.90%) was higher in the exposed group than that of the control group (22.71%, 0%, 45.45%, and 4.54%). A significant observation among the exposed group was that there was degradation in the quality of life. The outcome of the study would assist in monitoring and mitigation of machinery-induced vibration diseases (MIVD) in India and generally applicable to most of the mechanized mines as well. However, comprehensive studies are still needed to enunciate the magnitude extent. © 2020, Society for Mining, Metallurgy & Exploration Inc.
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    Study of devolatilization during chemical looping combustion of large coal and biomass particles
    (Elsevier B.V., 2020) Pragadeesh, K.S.; Iyyaswami, I.; Ruben Sudhakar, D.R.
    Chemical Looping Combustion (CLC) is one of the emerging technologies for carbon capture, with less energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC have limitations like loss of unconverted char and gaseous combustibles, which could be mitigated by use of coarser fuel particles. Devolatilization time is a critical input for the effective design of FB-CLC systems, primarily when large fuel particles are used. The present study investigates the devolatilization time and the char yield of three coals of two shapes, namely, two high ash Indian coals and a low ash Indonesian coal and a wood (Casuarina equisetifolia) in the size range of +8–25 mm, at different fuel reactor temperatures (800–950 °C) of a hematite based CLC unit. The devolatilization times of single fuel particles during CLC are determined using a visual method called ‘Color Indistinction Method’. Indonesian coal has the longest devolatilization time among the fuels, and biomass has the least. Increasing the bed temperature enhances the rate of volatile release, whereas this effect is less pronounced in larger particles. Devolatilization of Indonesian coal is found to be strongly influenced by the changes in operating conditions. With the decrease in sphericity, a maximum of 56% reduction in devolatilization time is observed for the +20–25 mm slender particles of Indonesian coals when compared to the near-round particles. The maximum average char yields at the end of the devolatilization phase for coal and biomass are about 55–76% and 16% respectively. Char yield in coal particles increases with an increase in particle size, whereas biomass particles show relatively consistent yield across all experimental conditions. Increase in bed temperature reduces the char yields of coal up to 12% and in biomass up to 30%. High volatile Indian coal is the most influenced fuel by the changes in fuels shape. A correlation for determining devolatilization time under CLC environment is presented, and it successfully fits most of the experimental values within ±20% deviation for coals (R2 = 0.95) and within ±15% deviation for biomass (R2 = 0.97). © 2020 Energy Institute
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    Sonar mapping of abandoned water-logged underground coal mine and backfilling operation using underwater camera
    (Inderscience Publishers, 2021) Pal, S.K.; Tripathi, A.K.; Panda, S.; Palaniappan, S.K.
    The paper describes mine mapping and backfilling work carried out during field experimentations on simple hydraulic gravity blind backfilling method for the stabilisation of ground above old abandoned waterlogged underground coal mine of Eastern Coalfields Limited (ECL), India. The section of the abandoned mine to be backfilled was explored using the underwater remote operated vehicle (ROV) camera before actual backfilling work. The use of sonar imaging facility of the ROV camera for mapping of the underground waterlogged area to be backfilled is described. The plotting of gradual progress of sand bed as the filling progressed in different stages through different boreholes as monitored from surrounding camera boreholes is also described. © © 2021 Inderscience Enterprises Ltd.