Return Airway Research Articles

Mechanism of rock deformation and failure and monitoring analysis in water-rich soft rock roadway of western China

Aiming to get the strata behavior and stability rules of surrounding rock of the main return airway of Yushujing Coal Mine, convergence deformation of two sides and force of U-shaped steel yieldable support and bolt were monitored, and deformation of surrounding rock and mechanical characteristics of support structure were timely obtained to guide the information construction and optimize supporting parameters in water-rich soft rock roadway. The field monitoring results indicate the following. (1) Convergence displacement of rock surface increases with time continuity and shows surrounding rock’s intense rheological behavior. The original support scheme cannot control the large deformation and strongly rheological behavior; (2) Without backfilling, the U-shaped steel support begins to bear load after erecting for 4–7 days and increases rapidly in the first 30 days. The U-shaped steel support at the right shoulder and top of roadway bears a larger force and the left side and shoulder bears a smaller force; (3) The stress of bolt increasing over time and at the right shoulder of roadway has larger growth and value. The mechanism of rock deformation and the failure and strata behavior in water-rich soft rock roadway are revealed based on the results of the measured relaxation zone of surrounding rock, measured stresses, and the rock mechanics tests.

Study on the Integrated Pillarless Coal Production and Methane Extraction Technology

The paper main introduce the principle of integrated pillarlesss coal production and methane extraction technology, the gas flow characteristics of stope and the coal production and methane extraction technology. In order to solve the mine production replacement problems under the high stress and high gas conditions in the deep mine, integrated pillarlesss gob-side entry retaining in return airway and "Y" type ventilation industrial trial were conducted. The integrated pillarlesss entry retaining could keep the road in a support pressure reduced area. The back filled mass could be effective to isolate the gas in the goaf and the application of "Y" type ventilation could highly reduce the gas content in the top corner.

Application of Y+L Ventilation to Gas Control on 3303 Mining Face

Mine ventilation is one of the most fundamental measures preventing gas accumulation. Through analyzing the advantages and disadvantages of Y-type ventilation, the paper proposed and practiced Y+L ventilation after relevant study and investigation when traditional Y-type ventilation only could not solve the gas problem on workface of Hexi Mine, i.e. to adopt the technique of maintaining airway along roadway, arranging airway as the return airway on work face, and to dig the transportation roadway of the next work face n advance as the tail roadway of 3303 work face, so as to jointly form the Y+L ventilation pattern of the mining face. This method is applied to the gas control of 3303 work face.

Field Test Research on Two-dimensional Gas Concentration and Temperature Distribution in the Goaf of Fully Mechanized Caving Face

The gas, oxygen, carbon monoxide and acetylene concentration and the temperature distribution of longwall goaf areas were analyzed by means of burying pipes and temperature sensor. Furthermore, the regulation of “three zones” distribution of 1361 face in Jinyuan colliery by the oxygen concentration and the temperature distribution has been worked out, and the limited velocity of the working face has been marked off. The research results showed that the gas concentration was low intake airflow roadway along goaf towards direction. The goaf gas concentration in return airway was far higher than intake airflow roadway. There was not combustion phenomenon during the test in the 1361 goaf of the coal mining. Meanwhile, the results also confirmed mining extraction process source of gas accumulation in face corner, also can be used for providing the basis of enacting fire prevention measures in the goaf and gas management measures for face corner.

Measurement and Analysis of Air Resistance on Baishan Coalmine

The test on mine ventilation system resistance is an important task of coalmine safety production and ventilation safety management, and the size of the air resistance will affect ventilation directly. In view of the current situation of Baishan ventilation system, we selected 11 main test lines combined with practical application, to test on the ventilation system via adopting precision barometer of point test, by which we got a comprehensive result on the distribution condition of coalmine ventilation system. By analysizing results show as follows: the distribution of Baishan ventilation system resistance is basically reasonable, air quantity is able to meet actual production of the mine and the resistance centers in return airways. Finally, the author puts forward some rational suggestion for the stability of Baishan ventilation system.

Analyses of Actual Measurement and Numerical Simulation on Gently Inclined Thin Seam

Based on the numerical simulation method and actual measurement analyses, characteristics of working face mineral pressure of the River Mouth Mine has been analyzed and this paper has obtained the following results: First weighting step of the main roof is 23.2 m, the average dynamic pressure coefficient is 1.54~1.74, mine strata behaviors is fiercer; hydraulic prop’s average working resistance is 45.72 KN of each, which indicates hydraulic prop’s working resistance has larger surplus coefficient, some measures should be taken to increase utilization ratio; advanced support length of return airway and mechanical roadway should reach to 30 m, the method and results can be used to improve support pattern of working face and guide safety production.

Determining areas in an inclined coal seam floor prone to water-inrush by micro-seismic monitoring

The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer. Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor. We have used a high-precision micro-seismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor, especially an inclined coal seam floor, may be more accurately estimated by monitoring the continuous, dynamic failure of the floor. The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway (the lower crossheading) is deeper and that the failure range is wider here compared to the coal seam floor near the return airway (the upper crossheading). The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified. This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.

Inert Technology Application for Fire Treatment in Dead End Referred to High Gassy Mine

The fire accident of the return airway for 7th mining area in TaoYi occurred in the middle section of the dead-end roadway referred to high gassy mine, which is difficult to handle and the technology request is high. Based on analysis of accident characteristics, a technology solution related to inerting and asphyxia was put forward, which combined the methods of underground injecting the inert gases into the fire area with the method of overground injecting the nitrous. After the injecting, the concentration of oxygen in the fire area reduced and the gas was asphyxial, which eliminated the danger of gas explosion and avoided expanding the accident. The successful application of this technology can provide references for the treatment of other similar fire accidents.

Research on a New Fast Airtight Device for Mine Fire

To overcome the disadvantage of existing fast airtight devices, a latest-model airbag type fast airtight device was devised. Operating principle, structure and installation procedure of the device are presented in detail. Based on related technical parameters of return airway section on working face 15108 of Shi Gang Coal Mine, ANSYS analysis model was created. With a certain pressure and temperature condition, stress and strain in x, y and z directions of the airbag were calculated and the results proved the feasibility of the design proposal. Through field test and analysis of experiment results, the advantage and disadvantage of the latest-model fast airtight device were summarized, in hope to offer some inspiration to the development of airbag type mine airtight device.

Analysis on characteristics of damaged field of surrounding rock and face of FMTC

Numerical simulation-FLAC3D and equivalent material simulation were carried out to analyze the damaged patterns and lows, distribution of plastic width of face, and surrounding rock of FMTC during the advance of work face with different thick coal seams based on engineering geology and exploitation technology of 1151(3) fully mechanized top-coal caving (FMTC) face in Xieqiao Colliery. The results show that there is damage, and the destruction characteristics of surrounding rock and coal mass are different obviously in asymmetric exploitation layout. The damaged zone in surrounding rock and the coal of the return airway is larger than that of the intake airway. Moreover, the retained coal pillars are all damaged by tension and shear fracture, and plastic zone in coal mass in the dip direction ahead of Face is nonuniform. There are large damage zones in roof and floor strata, surrounding rock, and coal of return and intake airways near work face. The damaged zone in the upper part of Face is larger than that in middle and lower parts. The fruits of this paper are of guiding significance for engineering practices, such as support design and choice, roadway supporting and maintaining, rock pressure control of FMTC face, etc.

Optimum location of surface wells for remote pressure relief coalbed methane drainage in mining areas

Based on engineering tests in the Huainan coal mining area, we studied alternative well location to improve the performance of surface wells for remote pressure relief of coalbed methane in mining areas. The key factors, affecting location and well gas production were analyzed by simulation tests for similar material. The exploitation results indicate that wells located in various positions on panels could achieve relatively better gas production in regions with thin Cenozoic layers, low mining heights and slow rate of longwall advancement, but their periods of gas production lasted less than 230 days, as opposed to wells in regions with thick Cenozoic layers, greater mining heights and fast rates of longwall advancement. Wells near panel margins achieved relatively better gas production and lasted longer than centerline wells. The rules of development of mining fractures in strata over panels control gas production of surface wells. Mining fractures located in areas determined by lines of compaction and the effect of mining are well developed and can be maintained for long periods of time. Placing the well at the end of panels and on the updip return airway side of panels, determined by lines of compaction and the effect of mining, would result in surface wells for remote pressure relief CBM obtaining their longest gas production periods and highest cumulative gas production.

The Effect of Low-Dose Inhaled Budesonide on Pc20 Amp Levels in Patients with Mild Asthma: A 3-Month Follow-Up Study

Adenosine monophosphate (AMP) challenge is a diagnostic tool for asthma. The aim of this study is to evaluate the effect of low dose inhaled budesonide (IB) on PC20AMP levels. Seventeen stable mild asthmatic patients were prospectively recruited. After initial testing, patients were administered 400 μ g of inhaled budesonide. AMP challenge was then repeated at the 12th hour and 5th,15th, 30th, and 90th days of the treatment. AMP challenge resulted in negative in 47% of the patients at 12−hour testing. This study suggests that low-dose IB may return airway responsiveness as early as 12 hours and AMP challenge may be effectively used for treatment monitorization.

Side abutment pressure distribution by field measurement

Given the 7123 working face in the Qidong Coal Mine of the Wanbei Mining Group, nine dynamic roof monitors were installed in the crossheading to measure the amount and velocity of roof convergence in different positions and at different times and three steel bored stress sensors were installed in the return airway to measure rock stress at depth. On the basis of this arrangement, the rule of change of the distribution of the side abutment pressure with the advance of the working face and movement of overlying strata was studied. The rule of change and the stability of rock stress at depth were measured. Secondly, the affected area and stability time of the side abutment pressure were also studied. The results show that: 1) During working, the face advanced distance was from 157 m to 99 m, the process was not effected by mining induced pressure. When the distance was 82 m, the position of peak stress was 5 m away from the coal wall. When the distance was 37 m, the position of peak stress away from the coal wall was about 15 m to 20 m and finally reached a steady state; 2) the time and the range of the peak of side rock pressure obtained from stress sensors were consistent with the results from the dynamic roof monitors; 3) the position of the peak pressure was 25 m away from the coal wall.

Research on sustenance of soft rock tunnel in Hongmiao Mine of Pingzhuang Mine Area

The return airway tunnel of bank 6 is an important tunnel for air return and auxiliary transportation. While under construction, the tunnel was seriously deformed, and the bottom was heavily squeezed. When completed, the bottom was smoothed out several times and a lot of maintenance were done. But about half year later, the tunnel collapsed. To counter the problems mentioned above, we systematically expounded our ideas and designed for solving the problem of the sustenance of the return airway tunnel of section 6.

Use of a Directional Spray System Design to Control Respirable Dust and Face Gas Concentrations Around a Continuous Mining Machine

A laboratory study assessed the impacts of water spray pressure, face ventilation quantity, and line brattice setback distance on respirable dust and SF6 tracer gas concentrations around a continuous mining machine using a sprayfan or directional spray system. Dust levels were measured at locations representing the mining machine operator and the standard and off-standard shuttle car operators, and in the return airway. The results showed that changes in all three independent variables significantly affected log-transformed dust levels at the three operator sampling locations. Changes in setback distance impacted return airway dust levels. Laboratory testing also identified numerous variable interactions affecting dust levels. Tracer gas levels were measured on the left and right sides of the cutting drum and in the return. Untransformed gas levels around the cutting drum were significantly affected by changes in water pressure, face ventilation quantity, and setback distance. Only a few interactions were identified that significantly affected these concentrations. Gas levels in the return airway were grouped by face ventilation quantity. Return gas levels measured at the low curtain quantity were generally unaffected by changes in water pressure or curtain setback distance. At the high curtain quantity, return airway gas levels were affected by curtain setback distance. A field study was conducted to assess the impact of these parameters in an actual mining operation. These data showed that respirable dust levels may have been impacted by a change in water pressure and, to a lesser extent, by an increase in curtain setback distance. A series of tracer gas pulse tests were also conducted during this study. The results showed that effectiveness of the face ventilation was impacted by changes in curtain flow quantity and setback distance. Laboratory testing supported similar conclusions.

ANALYSIS OF POTENTIAL ERRORS IN DETERMINATION OF COAL MINE ANNUAL METHANE EMISSIONS

Mineral Resources EngineeringVol. 09, No. 04, pp. 465-474 (2000) No AccessANALYSIS OF POTENTIAL ERRORS IN DETERMINATION OF COAL MINE ANNUAL METHANE EMISSIONSJAN M. MUTMANSKY and YANBEI WANGJAN M. MUTMANSKYThe Pennsylvania State University, Department of Energy and Geo-Environmental Engineering, University Park, PA 16802, USA Search for more papers by this author and YANBEI WANGThe Pennsylvania State University, Department of Energy and Geo-Environmental Engineering, University Park, PA 16802, USA Search for more papers by this author https://doi.org/10.1142/S095060980000038XCited by:3 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThe measurement of methane content and air quantity in each mine return airway is performed periodically in all underground coal mines in the United States. These periodic measurements are then combined to estimate the annual emission of methane into the atmosphere. A statistical study of some Appalachian underground coal mines with moderate to high levels of methane was conducted to determine the potential errors in annual emissions calculations.This paper analyses the accuracy and precision of annual methane emission calculations by assessment of each set of measurements used to produce an annual estimate. This includes analysis of the methane content determinations, the air quantity measurements, and the calculations to determine the annual emission. The final combination of measured values is tested by simulating annual emission calculations using the Monte Carlo method. Finally, the effect of each of these three variables on the annual emission values is evaluated and conclusions are made. FiguresReferencesRelatedDetailsCited By 3Closed coal mine shaft as a source of carbon dioxide emissionsPaweł Wrona, Zenon Różański, Grzegorz Pach, Tomasz Suponik and Marcin Popczyk8 August 2016 | Environmental Earth Sciences, Vol. 75, No. 15A new approach to estimate fugitive methane emissions from coal mining in ChinaYiwen Ju, Yue Sun, Zhanyou Sa, Jienan Pan and Jilin Wang et al.1 Feb 2016 | Science of The Total Environment, Vol. 543Fugitive greenhouse gas emissions in ventilation air from Australian underground coal minesStuart Day, Robyn Fry and Brendan Halliburton1 Sep 2012 | Greenhouse Gas Measurement and Management, Vol. 2, No. 2-3 Recommended Vol. 09, No. 04 Metrics History PDF download

Analysis of Potential Errors in Determination of Coal Mine Annual Methane Emissions

Mineral Resources EngineeringVol. 09, No. 04, pp. 465-474 (2000) No AccessANALYSIS OF POTENTIAL ERRORS IN DETERMINATION OF COAL MINE ANNUAL METHANE EMISSIONSJAN M. MUTMANSKY and YANBEI WANGJAN M. MUTMANSKYThe Pennsylvania State University, Department of Energy and Geo-Environmental Engineering, University Park, PA 16802, USA Search for more papers by this author and YANBEI WANGThe Pennsylvania State University, Department of Energy and Geo-Environmental Engineering, University Park, PA 16802, USA Search for more papers by this author https://doi.org/10.1142/S095060980000038XCited by:3 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThe measurement of methane content and air quantity in each mine return airway is performed periodically in all underground coal mines in the United States. These periodic measurements are then combined to estimate the annual emission of methane into the atmosphere. A statistical study of some Appalachian underground coal mines with moderate to high levels of methane was conducted to determine the potential errors in annual emissions calculations.This paper analyses the accuracy and precision of annual methane emission calculations by assessment of each set of measurements used to produce an annual estimate. This includes analysis of the methane content determinations, the air quantity measurements, and the calculations to determine the annual emission. The final combination of measured values is tested by simulating annual emission calculations using the Monte Carlo method. Finally, the effect of each of these three variables on the annual emission values is evaluated and conclusions are made. FiguresReferencesRelatedDetailsCited By 3Closed coal mine shaft as a source of carbon dioxide emissionsPaweł Wrona, Zenon Różański, Grzegorz Pach, Tomasz Suponik and Marcin Popczyk8 August 2016 | Environmental Earth Sciences, Vol. 75, No. 15A new approach to estimate fugitive methane emissions from coal mining in ChinaYiwen Ju, Yue Sun, Zhanyou Sa, Jienan Pan and Jilin Wang et al.1 Feb 2016 | Science of The Total Environment, Vol. 543Fugitive greenhouse gas emissions in ventilation air from Australian underground coal minesStuart Day, Robyn Fry and Brendan Halliburton1 Sep 2012 | Greenhouse Gas Measurement and Management, Vol. 2, No. 2-3 Recommended Vol. 09, No. 04 Metrics History PDF download

Evaluation and Control of Employee Exposure to Diesel Particulate at Several Australian Coal Mines

Abstract Employee exposures to diesel particulate (DP) were measured under normal and abnormal mining operations at BHP Steel Collieries Tower Colliery and other underground coal mines in New South Wales coal fields. DP was measured using submicron samplers developed by the U.S. Bureau of Mines, and the results were verified using quantitative scanning electron microscopy. Personal monitoring (n = 480 full-shift samples) conducted at nine underground coal mines has indicated that the exposure of the work force ranges from less than 0.1 to 2.2 mg/m3 of DP, depending on job type and mining operation. Operations such as longwall moves and stonedusting, which generate elevated levels of dust, cause severe interference to submicron DP measurements. Based on previous knowledge that engine tune and condition affect the balance between gaseous and particulate emissions, five technologies for controlling DP were investigated in a combination of studies conducted in an above-ground simulated tunnel and in a special controlled section of underground mine roadway. Potential improvements were validated by application in standard coal mining operations at Tower Colliery. Tests conducted under controlled conditions indicate that, depending on fuel quality, levels of DP in return airways can be reduced by up to 50 percent, and in actual mining situations a reduction of 20 percent can be achieved in exposure of the work force by the use of low sulfur fuels. In addition, subjective responses from the work force indicate that exhaust emissions from low sulfur fuels provide lower irritation and a more pleasant aroma. The use of water-filled scrubber tanks reduces the level of DP emissions by 25 percent. In addition, it was found that the cleanliness of these tanks in general does not affect their scrubbing properties. Chemical decoking of engines resulted in a reduction of 20 percent in DP in return airways. However, the longterm benefits and cost effectiveness of this treatment in mining operations have yet to be established. A nonflammable, disposable dry exhaust filter constructed from synthetic organic fibers with an operational lifetime in excess of 20 hours was found to reduce DP exhaust emissions by 80 percent. Investigations have indicated that the use of increased ventilation to control DP levels does not follow a simple dilution factor, and in some instances compliance with current regulatory requirements may not produce the required reduced exposure levels. The results from single-component control strategies provide considerable reduction in exposure to DP. However, the most efficient and cost-effective control methodology is the use of a combination of individual systems modeled to operations conducted at each mine.

Controlled recirculation in Canadian underground potash mines

Increasing energy costs and the need to conserve energy compounded with low mineral prices have prompted some Canadian mines to examine their energy-consuming operations and identify potential energy saving methods. Reusing or recirculating a fraction of ventilating airflow may make it possible for these mines to reduce heating costs. Such a study was conducted at Rocanville Division of Potash Corporation of Saskatchewan to determine the feasibility of controlled recirculation for reducing winter heating costs by reducing the intake airflows. This study was divided into two parts: the first involved taking measurements of mine contaminants in the return and intake airways, the second was monitoring air quality during a recirculation trial. Recirculation of air was created by opening an existing ventilation door located between the return and intake airways. Two shifts were continuously monitored in the return airways and the local recirculation experiment was carried out for five hours while a continuous miner was cutting. With the recirculation system in operation, a slight increase in temperature (1.00°C) was recorded between the intake and mixed intake. The overall quality of the exhaust air was found to be unchanged within the measurement limits despite the high percentage recirculation. A 5% increase in dustiness in the mixed intake was recorded. The results obtained from these studies indicate that controlled recirculation of return air is feasible. Some of the results from this work are illustrated and discussed.

Time variations of dust concentration and elemental composition in a gold mine

Dust samples were collected over a period of several weeks on a continuously moving strip of membrane filter (Florida State University streaker sampler type) in the return airway of an underground gold mine. The filters were then analysed stepwise by particle-induced X-ray emission (PIXE), yielding elemental concentrations in the dust at 2 h intervals. Elements measured include Al, Si, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn and Pb. Time sequence and average diurnal plots of elemental concentrations are presented. Results of multi-variate factor analysis provide insight into the source processes and materials. The possible sources of the Cl, Pb, Ca and Zn components in the dust are discussed, as is the relevance of these results to the proposed introduction of a gravimetric dust standard for South Africa gold mines. The results are presented to show how the quartz content of airborne dust may be estimated using energy-dispersive X-ray elemental measurements of Si, Al and K.