scholarly journals Horizontal Subzone Characteristics and Methane Seepage Properties of the Gas Flowing Fracture Zone above the Gob

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Wei Qin ◽  
Jialin Xu
Keyword(s):  
Fracture Zone ◽  
Gas Flow ◽  
Physical Simulation ◽  
Morphological Development ◽  
Flow State ◽  
Ring Fracture ◽  
Methane Seepage ◽  
Mining Depth ◽  
Seepage Properties ◽  
Mining Height

Gas flowing fracture zone (GFFZ) is an active zone in the gob where pressure-relieved methane can move freely. However, there are very few research findings on the horizontal development characteristics and internal methane seepage properties of GFFZs. In this paper, based on the development height of a GFFZ above the gob, the GFFZ was horizontally divided into the following: a lateral fracture subzone, an O-ring fracture subzone, and a compacted subzone. The identification criteria for all of these horizontal subzones were given by analyzing the influence of the stress in the coal rock mass on the development of mining-induced fractures. A numerical simulation study was conducted to determine the influences of the mining height and mining depth on the morphological development of all horizontal subzones of the GFFZ, and the simulation results showed that the mining height was the main factor influencing the development characteristics of horizontal subzones of the GFFZ. Both the maximum distance of the lateral fracture subzone beyond the mining boundary and the width of the O-ring fracture subzone increased with the increase of mining height. A physical simulation experiment was performed for extraction of gob methane through a surface borehole, and the experimental results showed that the gas flow state was laminar within the range of the lateral fracture subzone and the compacted subzone but that the gas flow state was turbulent, not following Darcy’s law, within the range of the O-ring fracture subzone.

Research on Influence of Loose Coverage Rock Fragment Distribution

2013 ◽  
Vol 405-408 ◽  
pp. 322-325
Author(s):  
Guo Jian Zhang ◽  
De Zhong Wang ◽  
Zhi Qiang Zhang
Keyword(s):  
Physical Simulation ◽  
Underground Mines ◽  
Rock Fragment ◽  
Mining Method ◽  
Rock Powder ◽  
Mining Depth ◽  
Sublevel Caving ◽  
Long Time ◽  
Fragment Distribution ◽  
Mining Work

The sublevel caving mining method is widely applied in China's underground mines, in particular of iron mines. Its mining work is under the protection of loose coverage rock. The loose coverage rock is located in the stope for a long time, and its frequently squeezed from production blasting, impact effect and the colliding and breaking in the falling process, it comes into being a large number of powder and small pieces of rocks. The rock powder and small fragments have such characteristics-good mobility and strong permeability. With the increasement of mining depth, the rock powder and small fragments in the loose coverage rock will be earlier to reach the ores than the big fragments of the same level. As a result, ore dilution will prematurely appear. To better know the phenomenon, this paper explores ore dilution of different fragment distribution of loose coverage rock by physical simulation experimental method. The research results have certain guiding significance for the actual production of underground mines.

Development Rule of Full-Mechanized Caving Mining Water-Flowing Fracture Zone in Yanzhou Mining Area

2012 ◽  
Vol 616-618 ◽  
pp. 475-480
Author(s):  
Zhen Li Fan ◽  
Bing Nan Hu
Keyword(s):  
Fracture Zone ◽  
Influence Factors ◽  
Mining Area ◽  
Overburden Rock ◽  
Rock Destruction ◽  
Thick Coal Seam ◽  
Hard Roof ◽  
Mining Depth ◽  
The Face ◽  
Mining Water

The heights of fully-mechanized mining water-flowing fracture zone of Yanzhou mining area were measured by borehole simple hydrology method .In order to confirm the influence degree of the geology and mining factors to the damage height of overburden rock , the paper analyses the measured data by using grey relation analysis theory, and concludes that the face span, mining thickness and mining depth are main influence factors to the height of the water-flowing fracture zone. On this basis, the paper reveals the general rules of fully-mechanized caving mining overburden rock destruction with the on conditions of gentle dip, thick coal seam and hard and medium hard roof by using regression analysis method.

scholarly journals Technical note: Mobile open dynamic chamber measurement of methane macroseeps in lakes

2020 ◽  
Vol 24 (12) ◽  
pp. 6047-6058
Author(s):  
Frederic Thalasso ◽  
Katey Walter Anthony ◽  
Olya Irzak ◽  
Ethan Chaleff ◽  
Laughlin Barker ◽  
...  
Keyword(s):  
Gas Flow ◽  
Ice Cores ◽  
Technical Note ◽  
Ch4 Emissions ◽  
Methane Seepage ◽  
Radiocarbon Data ◽  
Flux Measurements ◽  
Gaseous Hydrocarbons ◽  
Moderate Cost ◽  
Warming World

Abstract. Methane (CH4) seepage (i.e., steady or episodic flow of gaseous hydrocarbons from subsurface reservoirs) has been identified as a significant source of atmospheric CH4. However, radiocarbon data from polar ice cores have recently brought into question the magnitude of fossil CH4 seepage naturally occurring. In northern high latitudes, seepage of subsurface CH4 is impeded by permafrost and glaciers, which are under an increasing risk of thawing and melting in a globally warming world, implying the potential release of large stores of CH4 in the future. Resolution of these important questions requires a better constraint and monitoring of actual emissions from seepage areas. The measurement of these seeps is challenging, particularly in aquatic environments, because they involve large and irregular gas flow rates, unevenly distributed both spatially and temporally. Large macroseeps are particularly difficult to measure due to a lack of lightweight, inexpensive methods that can be deployed in remote Arctic environments. Here, we report the use of a mobile chamber for measuring emissions at the surface of ice-free lakes subject to intense CH4 macroseepage. Tested in a remote Alaskan lake, the method was validated for the measurement of fossil CH4 emissions of up to 1.08 × 104 g CH4 m−2 d−1 (13.0 L m−2 min−1 of 83.4 % CH4 bubbles), which is within the range of global fossil methane seepage and several orders of magnitude above standard ecological emissions from lakes. In addition, this method allows for low diffusive flux measurements. Thus, the mobile chamber approach presented here covers the entire magnitude range of CH4 emissions currently identified, from those standardly observed in lakes to intense macroseeps, with a single apparatus of moderate cost.

scholarly journals The effects of methane seepage at an intertidal/shallow subtidal site on the shore of the Kattegat, Vendsyssel, Denmark

1994 ◽  
Vol 41 ◽  
pp. 65-79
Author(s):  
P. R. Dando ◽  
S. C. M. O'Hara ◽  
S. J. Niven ◽  
U. Schuster ◽  
L. J. Taylor ◽  
...  
Keyword(s):  
Hydrogen Sulphide ◽  
Gas Flow ◽  
Interstitial Water ◽  
Nematode Species ◽  
Water Circulation ◽  
Oxidation Rates ◽  
Methane Seepage ◽  
Sulphide Concentration ◽  
Gas Seepage ◽  
Shallow Subtidal

The effects of methane gas seepage were studied at an intertidal/shallow subtidal site on the Kattegat coast of Denmark. A 30 m wide zone, containing approximately 65 gas seeps, extended over 70 m seawards from the shore. This was characterised by the presence of slabs, pavement and small pillars of carbonate-cemented sandstone which formed a partially buried reef. The escaping gas contained 91-100% methane with some carbon dioxide, 0.6--0.9%, and hydrogen sulphide. The hydrogen sulphide concentration varied over time and between individual seeps. Gas flow rates of individual seeps ranged up to 211 h-1 and the estimated total flow was 110 I h-1• Seeps were often stopped by sand movement, but the overall gas flow from the site appeared to be constant. The escaping gas generated an interstitial water circulation and drew overlying seawater into the sediment. Water pumped out by the seeps was enriched in phosphate and ammonia. Sulphate reduction rates in the seep area were 1.1-17.1 m moles sulphate reduced and aerobic methane oxidation rates were 0.2 - 5.5 m moles methane consumed m-2 day-1• The composition of the flora and fauna surrounding the seeps was affected by the presence of hard substrate (the cemented sandstone). Epifauna was more abundant in the seep zone than else­where, whereas the macrobenthic infauna was reduced in the seep zone, possibly due to the cementation. The sediment was almost devoid of meiobenthic organisms, except nematodes. Nematode species numbers, abundance and biomass were lower at the seeps than 5-20 cm away. The nematode fauna penetrated deeper into the sediment close to the seeps than at the seeps themselves. This is explained by the interstitial water circulation at and close to the seeps. 14C measurements showed that little methane carbon was entering the food web surrounding the seeps.

scholarly journals Key Stratum Structure and Support Working Resistance of Longwall Face with Large Mining Height in the Shallow Coal Seams, China

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Qingxiang Huang ◽  
Jinlong Zhou ◽  
Jian Cao
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Longwall Face ◽  
Beam Structure ◽  
Key Stratum ◽  
Immediate Roof ◽  
Large Mining Height ◽  
Shallow Coal Seam ◽  
Working Resistance ◽  
Mining Height

The fully mechanized mining with large mining height is the main method for high yield and efficient coal mining in China. The key stratum structure (KSS) is the basis of revealing the mechanism of roof weighting and determination of support working resistance of the longwall face with large mining height (LFLMH) in the shallow coal seam. The height of the caving zone at LFLMH is large, the thick immediate roof forms the “short cantilever beam” structure commonly, and the hinge layer of the overlying key stratum will move upward to the higher position. The “high position oblique step voussoir beam” structure of single-key stratum (SKS) and “oblique step voussoir beam and voussoir beam” structure of double-key stratum (DKS) in the shallow coal seam were proposed with physical simulation and Universal Distinct Element Code (UDEC). The analysis of the KSS and numerical simulation reveals the mechanism of strong roof weighting at the SKS longwall face and large-small alternate periodic weighting at the DKS longwall. It is concluded that the large static load caused by the “equivalent immediate roof (EIR)” is the basic load, and the instability load of the KSS is the additional dynamic load of support. Besides, the calculation methods of the reasonable support working resistance at LFLMH were obtained and verified with engineering applications.

scholarly journals Research on Overburden Movement Characteristics of Large Mining Height Working Face in Shallow Buried Thin Bedrock

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4208 ◽  
Author(s):  
Qingxiang Huang ◽  
Yanpeng He
Keyword(s):  
Physical Simulation ◽  
Mining Area ◽  
Engineering Problem ◽  
Dynamic Crack ◽  
Working Face ◽  
Time Space ◽  
Movement Distance ◽  
Large Mining Height ◽  
Thin Bedrock ◽  
Mining Height

The overburden movement of the large mining height working face of shallow buried thin bedrock (SBTB) is a complex engineering problem with “time-space-intension”, which is of great significance to realize efficient and safe mining in the northern Shaanxi mining area. Based on the research object of No. 22201 working face in Zhangjiamao Coal Mine, the roof structure characteristics of large mining height working face in SBTB are researched by field drilling measurement, laboratory test, physical and numerical simulation. The results show that: (1) Based on the measured data of the drillholes, it is concluded that under the mining conditions of SBTB with large mining height, the roof movement is ahead of the weighting of the working face, and the working resistance has a significant time effect. The advanced movement distance is about 20 m, which can be used as an early warning index of the weighting. The lag movement distance in the roof with horizon of 30 m is two periodic weighting intervals, which are about 26 m. (2) The first weighting interval of the working face is 32 m. The roof first break has obvious step sinking phenomenon, and the measured surface appears at a position 45 m away from the transport slot. It is statistically concluded that the periodic weighting interval is 9.5~16.5 m, the average weighting interval is 13 m, which is equivalent to the periodic dynamic crack spacing of the surface. (3) The results of field measurement and physical simulation show that the breaking angle of the roof of the No. 22201 large mining height is about 66°, and the periodic stepping distance of the T-junction suspension area is 6~8m. Along the strike of the working face, the roof breaking is mainly arc arched. The research results ensure the safe and green mining of shallow coal seam.

Physical Simulation on the Liquid Metal Flow in FC-Mold of Slab Continuous Casting

2011 ◽  
Vol 402 ◽  
pp. 46-50
Author(s):  
Zhen Qiang Zhang ◽  
Hao Jia ◽  
Xiao Wei Zhang ◽  
Kang Deng ◽  
Zhong Ming Ren ◽  
...  
Keyword(s):  
Liquid Metal ◽  
Magnetic Flux ◽  
Continuous Casting ◽  
Flux Density ◽  
Physical Simulation ◽  
Metal Flow ◽  
Magnetic Flux Density ◽  
Flow State ◽  
Control Effect ◽  
Liquid Metal Flow

The flow state and velocity distribution of liquid metal in the FC-Mold and the influence rules by the magnetic flux density have been investigated when electromagnetic brake adopted, applying mercury as medium to simulate molten steel in the continuous casting process. The velocity measurement has been completed by the Ultrasonic Doppler Velocimeter (UDV) under various magnetic distribution and the influence laws of magnetic flux density on the liquid metal flow in the mold has been analyzed. The experimental results indicate that, when the upper and lower magnetic flux density is 0.18T and 0.5T respectively, a preferable control effect can be obtained, not only the free surface fluctuation can be compressed, but also a plug flow can be rapidly formed.

scholarly journals Constitutive Model of Solid Backfill Materials and Numerical Simulation of Overburden Movement and Deformation in Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Chao Ma ◽  
Lianying Zhang ◽  
Bing Li ◽  
Xianbiao Mao
Keyword(s):  
Constitutive Model ◽  
Surface Subsidence ◽  
Compaction Process ◽  
Compaction Rate ◽  
Key Strata ◽  
Mining Depth ◽  
Backfill Mining ◽  
Backfill Materials ◽  
Initial Compaction ◽  
Mining Height

Solid backfill mining is an efficient and environmental-friendly coal mining technology, which can effectively solve the problems of coal gangue pollution, water resource loss, and surface subsidence. Based on the mechanical behavior of backfill materials in the compaction process, volume strain was used to express the deformation modulus, and a constitutive model of backfill materials was proposed in this study. The ABAQUS UMAT was used to develop the numerical calculation subroutine of the model. Finally, the rationality of the model was verified that simulated stress-strain curves of the backfill materials during the compaction process agree well with experiments. Based on the proposed constitutive model, the influence of three factors (the initial compaction rate of the filling body, the mining height, and the mining depth) on the key strata and surface subsidence was analyzed systematically. The results show that the initial compaction rate and the height of coal seams have significant influences on surface subsidence. When the thickness of topsoil is only changed and the structural composition and lithology of overburden are not changed, the mining depth has little influence on surface subsidence, but a significant influence on surface subsidence range. The influence of mining height and mining depth on the deformation of key strata of overburden and surface subsidence is approximately linear, while the influence of the initial compaction rate is nonlinear.

scholarly journals Fracture evolution and gas transport laws of coal and rock in one kilometer deep coal mine with complicated conditions

2019 ◽  
Vol 23 (Suppl. 3) ◽  
pp. 907-915
Author(s):  
Jianguo Zhang ◽  
Man Wang ◽  
Yingwei Wang
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Mine ◽  
Fracture Zone ◽  
Gas Flow ◽  
Gas Transport ◽  
Enhancement Effect ◽  
Gas Extraction ◽  
Coal Seams ◽  
Long Distance

As coal mining gradually extends deeper, coal seams in China generally show high stress, high gas pressure and low permeability, bringing more difficulty to coal mining. Therefore, in order to strengthen gas extraction, it is necessary to carry out reservoir reconstruction after deep coal seams reached. In this paper, the distribution and evolution laws of fracture zone overlaying strata of J15 seam in Pingdingshan No. 10 coal mine after excavation were studied by combining similar simulation and numerical simulation, meanwhile, the gas transport law within fracture zone was numerically simulated. The results show that the fracture zone reaches a maximum of 350 mm in the vertical direction and is 75 mm away from W9,10 coal seams in vertical distance. Since W9,10 coal seams are in an area greatly affected by the bending zone of J15 coal seam under the influence of mining, the mining of J15 coal seam will exert a strong permeability enhancement effect on W9,10 coal seams. The J15 coal seam can act as a long-distance protective layer of W9,10 coal seams to eliminate the outburst danger of the long-distance coal seams in bending zone with coal and gas outburst danger, thereby achiev?ing safe, productive and efficient integrated mining of coal and gas resources. The gas flux of mining-induced fractures in the trapezoidal stage of mining-induced fracture field is far greater than that in the overlaying stratum matrix. The horizontal separation fractures and vertical broken fractures within the mining-induced fracture field act as passages for gas-flow. Compared with gas transport in the overlaying stratum matrix, the horizontal separation fractures and vertical broken fractures within the mining-induced fracture field play a role in guiding gas-flow. The research results can provide theoretical support for the arrangement of high-level gas extraction boreholes in roof fracture zones.

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