Most of coal is produced from open-cut mines in Southeast Asian countries. However, the conditions of their surface mines are worsening each year： the stripping ratio is increasing, approaching economic ratio and the...Most of coal is produced from open-cut mines in Southeast Asian countries. However, the conditions of their surface mines are worsening each year： the stripping ratio is increasing, approaching economic ratio and the regulation of environmental protection. To meet the demand for coal, underground mines have to be developed in the near future. Under these circumstances, the development of new coal mines from open-cut highwalls are being planned in Southeast Asian Countries. Moreover, some of the Southeast Asian mines have thick coal seams. However, if the conventional mining systems and designs introduced in US, Australia and European Countries are applied, several geotechnical issues can be expected due to the mines＇ weak geological conditions. From these backgrounds, this paper proposed a punch multi-slice mining system with stowing for thick coal seam under weak geological conditions and discussed its applicability and suitable design by means of numerical analysis.展开更多
Accidents and injuries related to work are major occupational health problems in most of the industrialized countries.Traditional approaches to manage workplace safety in mines have mainly focused on job redesign and ...Accidents and injuries related to work are major occupational health problems in most of the industrialized countries.Traditional approaches to manage workplace safety in mines have mainly focused on job redesign and technical aspects of engineering systems.It is being realized that compliance to rules and regulations of mines is a prerequisite;however,it is not sufficient to achieve further reduction in accident and injury rates in mines.Proactive approaches are necessary to further improve the safety standards in mines.Unsafe conditions and practices in mines lead to a number of accidents,which in turn may cause loss and injury to human lives,damages to property,and loss of production.Hazard identification and risk assessment is an important task for the mining industry which needs to consider all the risk factors at workplaces.Applications of risk management approaches in mines are necessary to identify and quantify potential hazards and to suggest effective solutions.In this paper,the following risk estimation techniques were discussed:(i)DGMS(Directorate General of Mines Safety,India)risk rating criterion,and(ii)a matrix based approach.The proposed tools were demonstrated through an application in an opencast coal mine in India.It was inferred that the risk assessment approach can be used as an effective tool to indentify and control hazards in mines.展开更多
The effective diffusion coefficients in mine ventilation-flows had been obtained as 4 to 200 m^2/s by matching the measured concentration-time curves with the advec- tion-diffusion equation.The turbulent diffusion coe...The effective diffusion coefficients in mine ventilation-flows had been obtained as 4 to 200 m^2/s by matching the measured concentration-time curves with the advec- tion-diffusion equation.The turbulent diffusion coefficients in the simple airways have good agreement with the equation proposed by Taylor.However,for complex airways in operat- ing mines,the evaluated effective diffusion coefficients in the mines show higher values than that calculated by the Taylor's equation.A numerical simulation model using with movements of discrete particles dosed into ventilation flows has been developed to simu- late diffusion phenomena of gas or dust in mine airways.Numerical simulations had been conducted on distribution of tracers in single airways with ordinary profiles of mean velocity velocity fluctuations and Reynolds stress.As one of results,long band of diffused particles is obtained at the single airway of 600 m in length,and large effective diffusion coefficient is evaluated as 20 m^2/s.展开更多
The acid-base buffer characteristics of fulvic acid (FA) and barium fulvate (BaFA)were analyzed. Each share of the sample or model agents (phthalic acid and salicylic acid)were separately mixed into a series of shares...The acid-base buffer characteristics of fulvic acid (FA) and barium fulvate (BaFA)were analyzed. Each share of the sample or model agents (phthalic acid and salicylic acid)were separately mixed into a series of shares of dilute solutions of HCI or NaOH with a series of concentration. The original pH values of the solutions were arranged from 2 to 13.Final balanced pH of each share was measured. The pH changes show that FA and BaFApossess buffer ability, whereas the model agents do not. The tendency of balanced pHvalues was 5.4 for FA and 7.4 for BaFA, whereas the original pH was 4.0-8.5; balancedpH changed little. At room temperature, the maximum buffer capacities were as follows:18.11 mmol hydroxyl per gram FA, 11.25 mmol hydroxyl per gram BaFA, 1.19 mmol protonper gram FA, and 1.45 mmol proton per gram BaFA. Mathematics analysis shows thatlogarithm of buffer capacities of FA and BaFA is linearly dependent on original pH. Compared with BaFA and model agents, it is concluded that FA buffer capacity against hydroxylrelies not only on its acidic groups, BaFA buffer capacity against hydroxyl does not rely onits acidic groups, and FA buffer capacity against proton is not related with its carboxyl andphenolic hydroxyl group. The pH values of FA-water solutions with different concentrationsfrom 1 to 10 grams per liter were measured. Their pH values were slightly affected by itsconcentration. Thus, FA possesses a much stronger buffer ability against water dilutionthan common buffer agent. All the pH values of FA water solutions were very nearby 5.4,just the same as the balanced pH tendency for adding FA.展开更多
Maintaining stability as well as optimizing recovery of crown pillar, a pillar separating surface area with the uppermost stope in overhand cut and fill underground mining method, is important. Failures in stope may l...Maintaining stability as well as optimizing recovery of crown pillar, a pillar separating surface area with the uppermost stope in overhand cut and fill underground mining method, is important. Failures in stope may lead to crown pillar failures and cause surface subsidence. Increasing crown pillar thickness will increase crown pillar stability yet reduce mining recovery because part of crown pillar is formed by ore body. Preventing stope failure is the key to maintain stability and optimize recovery of crown pillar. Therefore, it is important to study countermeasure method for stope failure especially in crown pillar area. An attempt has been made to investigate the effectiveness of various countermeasures for stope failure in crown pillar area by means of parametric study. The result shows active type support system is effective for supporting stope in high vertical stress condition while the passive one needs to be installed if the stope is opened in high horizontal stress condition. In general, more supporting capacity from both type support systems is needed if the stope is opened in more severe geological condition. Another countermeasures, sill pillar and surface pile, are introduced for stope instability in crown pillar and non-crown pillar area. Sill pillar is an abandoned slice of unstable stope based on stability analysis. Sill pillar is very effective to stabilize stope both in crown pillar and non-crown pillar area, especially for stope in high horizontal stress condition. Sill pillar application in model with stress ratio 2 can optimize 20 meter thickness of crown pillar into 5 meter. Another proposed countermeasure is surface pile. Surface pile can be installed from the surface to improve stability of crown pillar and stope. The most effective use of surface pile is found in simulation of model with stress ratio 0.75 where surface pile can optimize 15 meter thickness of crown pillar into 5 meter.展开更多
Acid Mine Drainage (AMD) which occurs when sulfide minerals are exposed to water and oxygen with an excavation is one of the serious environmental problems in the world. A dry cover system is generally constructed in ...Acid Mine Drainage (AMD) which occurs when sulfide minerals are exposed to water and oxygen with an excavation is one of the serious environmental problems in the world. A dry cover system is generally constructed in waste dump for the prevention of AMD in Indonesia by virtue of low cost and availability of waste rocks for a cover layer. However, the failure of the system caused by the lack of information related to the construction of cover system in mines, which leads to AMD, has been reported recently in Indonesia. In this study, the field investigation was conducted in pit and waste dump in open cast coal mine in Indonesia with the aim of obtaining the information on the construction of a cover layer and backfilling conditions of waste rocks in the waste dump. The rock samples taken in two areas of the mine were analyzed by geochemical analysis and sequential extraction with acids. The results indicated that Net Acid Producing Potential (NAPP) of the rocks in the waste dump down to 100 cm depth in both areas was from 10 to 30 kg H<sub>2</sub>SO<sub>4</sub>/ton, suggesting that Potentially Acid Forming (PAF) was backfilled in a cover layer. The backfill of PAF was contrary to the concept of cover system, which caused the failure of constructing a cover layer. The cause of the failure was likely attributed to the shortage of cover rocks which are classified as Non Acid Forming (NAF) or the failure of proper placement of them by an operational problem in the areas. Moreover, the results of the extraction with acids suggested that the form of iron and sulfur has to be taken into account to discuss the occurrence of AMD.展开更多
Since 2011 Indonesia has become the world’s largest exporter of steam coal. Two supporting factors of Indonesia to be the largest exporter are its enormous production and low operating cost. This paper foresees the p...Since 2011 Indonesia has become the world’s largest exporter of steam coal. Two supporting factors of Indonesia to be the largest exporter are its enormous production and low operating cost. This paper foresees the production and extraction cost of Indonesian coal in the coming period to evaluate marketing policies and estimate the cost of Indonesian coal supply in domestic market as well as in export market. The production forecasting is carried out by Gompertz curve. Peak production of Indonesian coal is expected to take place in 2026. Moreover, the extraction cost in coal basins which produce high calorific value of coal, in accordance to the operating cost forecasting, is higher than the one with low calorific value of coal due to its higher stripping ratio. Three main basins of Central Sumatra, Tarakan, and Barito basins play major rule in supplying coal for domestic use in short term. And other coal basins such as South Sumatra, Kutai, Bengkulu, and Ombilin basins provide long term supply in the domestic and export markets.展开更多
This work presents the development of hierarchical niobium pentoxide(Nb_(2)O_(5))-based composite nanofiber membranes for integrated adsorption and photocatalytic degradation of methylene blue(MB)pollutants from aqueo...This work presents the development of hierarchical niobium pentoxide(Nb_(2)O_(5))-based composite nanofiber membranes for integrated adsorption and photocatalytic degradation of methylene blue(MB)pollutants from aqueous solutions.The Nb_(2)O_(5) nanorods were vertically grown using a hydrothermal process on a base electrospun nanofibrous membrane made of polyacrylonitrile/polyvinylidene fluoride/ammonium niobate(V)oxalate hydrate(Nb_(2)O_(5)@PAN/PVDF/ANO).They were characterized using field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD)analysis,and Fourier transform infrared(FTIR)spectroscopy.These composite nanofibers possessed a narrow optical bandgap energy of 3.31 eV and demonstrated an MB degradation efficiency of 96%after 480 min contact time.The pseudo-first-order kinetic study was also conducted,in which Nb_(2)O_(5)@PAN/PVDF/ANO nanofibers have kinetic constant values of 1.29×10^(-2) min^(-1) and 0.30×10^(-2) min^(-1) for adsorption and photocatalytic degradation of MB aqueous solutions,respectively.These values are 17.7 and 7.8 times greater than those of PAN/PVDF/ANO nanofibers without Nb_(2)O_(5) nanostructures.Besides their outstanding photocatalytic performance,the developed membrane materials exhibit advantageous characteristics in recycling,which subsequently widen their practical use in environmental remediation applications.展开更多
文摘Most of coal is produced from open-cut mines in Southeast Asian countries. However, the conditions of their surface mines are worsening each year： the stripping ratio is increasing, approaching economic ratio and the regulation of environmental protection. To meet the demand for coal, underground mines have to be developed in the near future. Under these circumstances, the development of new coal mines from open-cut highwalls are being planned in Southeast Asian Countries. Moreover, some of the Southeast Asian mines have thick coal seams. However, if the conventional mining systems and designs introduced in US, Australia and European Countries are applied, several geotechnical issues can be expected due to the mines＇ weak geological conditions. From these backgrounds, this paper proposed a punch multi-slice mining system with stowing for thick coal seam under weak geological conditions and discussed its applicability and suitable design by means of numerical analysis.
文摘Accidents and injuries related to work are major occupational health problems in most of the industrialized countries.Traditional approaches to manage workplace safety in mines have mainly focused on job redesign and technical aspects of engineering systems.It is being realized that compliance to rules and regulations of mines is a prerequisite;however,it is not sufficient to achieve further reduction in accident and injury rates in mines.Proactive approaches are necessary to further improve the safety standards in mines.Unsafe conditions and practices in mines lead to a number of accidents,which in turn may cause loss and injury to human lives,damages to property,and loss of production.Hazard identification and risk assessment is an important task for the mining industry which needs to consider all the risk factors at workplaces.Applications of risk management approaches in mines are necessary to identify and quantify potential hazards and to suggest effective solutions.In this paper,the following risk estimation techniques were discussed:(i)DGMS(Directorate General of Mines Safety,India)risk rating criterion,and(ii)a matrix based approach.The proposed tools were demonstrated through an application in an opencast coal mine in India.It was inferred that the risk assessment approach can be used as an effective tool to indentify and control hazards in mines.
基金the National Natural Science Foundation of China(50375026)
文摘The effective diffusion coefficients in mine ventilation-flows had been obtained as 4 to 200 m^2/s by matching the measured concentration-time curves with the advec- tion-diffusion equation.The turbulent diffusion coefficients in the simple airways have good agreement with the equation proposed by Taylor.However,for complex airways in operat- ing mines,the evaluated effective diffusion coefficients in the mines show higher values than that calculated by the Taylor's equation.A numerical simulation model using with movements of discrete particles dosed into ventilation flows has been developed to simu- late diffusion phenomena of gas or dust in mine airways.Numerical simulations had been conducted on distribution of tracers in single airways with ordinary profiles of mean velocity velocity fluctuations and Reynolds stress.As one of results,long band of diffused particles is obtained at the single airway of 600 m in length,and large effective diffusion coefficient is evaluated as 20 m^2/s.
文摘The acid-base buffer characteristics of fulvic acid (FA) and barium fulvate (BaFA)were analyzed. Each share of the sample or model agents (phthalic acid and salicylic acid)were separately mixed into a series of shares of dilute solutions of HCI or NaOH with a series of concentration. The original pH values of the solutions were arranged from 2 to 13.Final balanced pH of each share was measured. The pH changes show that FA and BaFApossess buffer ability, whereas the model agents do not. The tendency of balanced pHvalues was 5.4 for FA and 7.4 for BaFA, whereas the original pH was 4.0-8.5; balancedpH changed little. At room temperature, the maximum buffer capacities were as follows:18.11 mmol hydroxyl per gram FA, 11.25 mmol hydroxyl per gram BaFA, 1.19 mmol protonper gram FA, and 1.45 mmol proton per gram BaFA. Mathematics analysis shows thatlogarithm of buffer capacities of FA and BaFA is linearly dependent on original pH. Compared with BaFA and model agents, it is concluded that FA buffer capacity against hydroxylrelies not only on its acidic groups, BaFA buffer capacity against hydroxyl does not rely onits acidic groups, and FA buffer capacity against proton is not related with its carboxyl andphenolic hydroxyl group. The pH values of FA-water solutions with different concentrationsfrom 1 to 10 grams per liter were measured. Their pH values were slightly affected by itsconcentration. Thus, FA possesses a much stronger buffer ability against water dilutionthan common buffer agent. All the pH values of FA water solutions were very nearby 5.4,just the same as the balanced pH tendency for adding FA.
文摘Maintaining stability as well as optimizing recovery of crown pillar, a pillar separating surface area with the uppermost stope in overhand cut and fill underground mining method, is important. Failures in stope may lead to crown pillar failures and cause surface subsidence. Increasing crown pillar thickness will increase crown pillar stability yet reduce mining recovery because part of crown pillar is formed by ore body. Preventing stope failure is the key to maintain stability and optimize recovery of crown pillar. Therefore, it is important to study countermeasure method for stope failure especially in crown pillar area. An attempt has been made to investigate the effectiveness of various countermeasures for stope failure in crown pillar area by means of parametric study. The result shows active type support system is effective for supporting stope in high vertical stress condition while the passive one needs to be installed if the stope is opened in high horizontal stress condition. In general, more supporting capacity from both type support systems is needed if the stope is opened in more severe geological condition. Another countermeasures, sill pillar and surface pile, are introduced for stope instability in crown pillar and non-crown pillar area. Sill pillar is an abandoned slice of unstable stope based on stability analysis. Sill pillar is very effective to stabilize stope both in crown pillar and non-crown pillar area, especially for stope in high horizontal stress condition. Sill pillar application in model with stress ratio 2 can optimize 20 meter thickness of crown pillar into 5 meter. Another proposed countermeasure is surface pile. Surface pile can be installed from the surface to improve stability of crown pillar and stope. The most effective use of surface pile is found in simulation of model with stress ratio 0.75 where surface pile can optimize 15 meter thickness of crown pillar into 5 meter.
文摘Acid Mine Drainage (AMD) which occurs when sulfide minerals are exposed to water and oxygen with an excavation is one of the serious environmental problems in the world. A dry cover system is generally constructed in waste dump for the prevention of AMD in Indonesia by virtue of low cost and availability of waste rocks for a cover layer. However, the failure of the system caused by the lack of information related to the construction of cover system in mines, which leads to AMD, has been reported recently in Indonesia. In this study, the field investigation was conducted in pit and waste dump in open cast coal mine in Indonesia with the aim of obtaining the information on the construction of a cover layer and backfilling conditions of waste rocks in the waste dump. The rock samples taken in two areas of the mine were analyzed by geochemical analysis and sequential extraction with acids. The results indicated that Net Acid Producing Potential (NAPP) of the rocks in the waste dump down to 100 cm depth in both areas was from 10 to 30 kg H<sub>2</sub>SO<sub>4</sub>/ton, suggesting that Potentially Acid Forming (PAF) was backfilled in a cover layer. The backfill of PAF was contrary to the concept of cover system, which caused the failure of constructing a cover layer. The cause of the failure was likely attributed to the shortage of cover rocks which are classified as Non Acid Forming (NAF) or the failure of proper placement of them by an operational problem in the areas. Moreover, the results of the extraction with acids suggested that the form of iron and sulfur has to be taken into account to discuss the occurrence of AMD.
文摘Since 2011 Indonesia has become the world’s largest exporter of steam coal. Two supporting factors of Indonesia to be the largest exporter are its enormous production and low operating cost. This paper foresees the production and extraction cost of Indonesian coal in the coming period to evaluate marketing policies and estimate the cost of Indonesian coal supply in domestic market as well as in export market. The production forecasting is carried out by Gompertz curve. Peak production of Indonesian coal is expected to take place in 2026. Moreover, the extraction cost in coal basins which produce high calorific value of coal, in accordance to the operating cost forecasting, is higher than the one with low calorific value of coal due to its higher stripping ratio. Three main basins of Central Sumatra, Tarakan, and Barito basins play major rule in supplying coal for domestic use in short term. And other coal basins such as South Sumatra, Kutai, Bengkulu, and Ombilin basins provide long term supply in the domestic and export markets.
基金funded by the Minister of Education,Culture,Research,and Technology of Indonesia through a research scheme of“Penelitian Fundamental–Reguler(PFR)2023”under a contract number of 1115c/IT9.2.1/PT.01.03/2023.
文摘This work presents the development of hierarchical niobium pentoxide(Nb_(2)O_(5))-based composite nanofiber membranes for integrated adsorption and photocatalytic degradation of methylene blue(MB)pollutants from aqueous solutions.The Nb_(2)O_(5) nanorods were vertically grown using a hydrothermal process on a base electrospun nanofibrous membrane made of polyacrylonitrile/polyvinylidene fluoride/ammonium niobate(V)oxalate hydrate(Nb_(2)O_(5)@PAN/PVDF/ANO).They were characterized using field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD)analysis,and Fourier transform infrared(FTIR)spectroscopy.These composite nanofibers possessed a narrow optical bandgap energy of 3.31 eV and demonstrated an MB degradation efficiency of 96%after 480 min contact time.The pseudo-first-order kinetic study was also conducted,in which Nb_(2)O_(5)@PAN/PVDF/ANO nanofibers have kinetic constant values of 1.29×10^(-2) min^(-1) and 0.30×10^(-2) min^(-1) for adsorption and photocatalytic degradation of MB aqueous solutions,respectively.These values are 17.7 and 7.8 times greater than those of PAN/PVDF/ANO nanofibers without Nb_(2)O_(5) nanostructures.Besides their outstanding photocatalytic performance,the developed membrane materials exhibit advantageous characteristics in recycling,which subsequently widen their practical use in environmental remediation applications.
