A new cross‐borehole hydraulic caving technique in the coal seam with a soft layer for preventing coal and gas outbursts during coal roadway excavation

B1 coal seam located at -550m level in Liangbei Coal Mine is a typical "three-soft" seam. The coal roadway with a depth of 610-750m lies under the critical softening depth of the roadway, and its support difficulty coefficient is 1.5-2.0. The coal has poor air permeability, high gas content and high gas pressure, so danger degree of the gas outburst is relatively strong. The coal seam was destroyed in a disastrous state by more than 100 boreholes for gas outburst prevention during the excavation. This results in the difficulty in the roadway support. Engineering geological characteristics of the coal roadway at 11 mining area are introduced. Based on the engineering geo-mechanics method, the reasons of deformation and failure of the coal roadway are analyzed. In view of problems in excavation and support, as well as the type of the coal roadway deformation mechanism, the borehole parameters are optimized for the gas outburst prevention, and bolt-net-cable coupling support with high convex steel-belt is used to control the coal roadway stability at 11 mining area. Practice shows that the effect is fine.

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Diffraction Characteristics of Small Fault ahead of tunnel face in coal roadway

Earth Sciences Research Journal ◽

10.15446/esrj.v21n2.64938 ◽

2017 ◽

Vol 21 (2) ◽

pp. 95-99 ◽

Cited By ~ 6

Author(s):

Bo Wang ◽

Shengdong Liu ◽

Fubao Zhou ◽

Jun Zhang ◽

Fangkun Zheng

Keyword(s):

Acoustic Wave ◽

Coal Seam ◽

Fault Prediction ◽

P Wave ◽

Mine Safety ◽

Observation System ◽

Tunnel Face ◽

Coal Roadway ◽

Small Fault ◽

Channel Wave

Small fault ahead of the tunnel face in coal roadway is the important hidden hazard factor of coal and gas outburst accidents. The study of small fault prediction has important practical significance, which is the urgent demand of coal mine safety production. The diffraction of breakpoint can be used to identify the fault. However, unlike surface seismic exploration, the diffraction is with approximately horizontal incidence when the advanced detection is carried out in the roadway. The common advanced detection system is mainly as the reference of traffic tunnel, without considering the influence of low-velocity coal seam. Considering the influence of an acoustic wave of the roadway cavity and channel wave of the coal seam, the advanced detection model of small fault ahead of tunnel face is established. Diffraction advanced observation system in which sources located in front of tunnel face is constructed, and the numerical calculation of the high-order staggered-grid finite difference is carried out. The simulation results show that: Compared with the data collected by reflection observation system, in seismic records acquired by diffraction observation system, the suppression effect of acoustic wave is appeared. The diffracted P-wave of the breakpoint of component X is clear with strong energy and short-wave group. Multiple diffractions of the breakpoint are not found, but the multiple diffraction of tunnel face endpoint is obvious. The difference between breakpoint diffraction and multiple diffractions of the endpoint is clear, and diffracted P-wave of the breakpoint is easy to identify. The multiple reflected channel wave between the fault and the tunnel face is very obvious, and the reflected channel wave of small fault is so hard to identify. Migration results show that the imaging resolution of diffracted P-wave of small fault is higher than the reflected channel wave, and breakpoint location of imaging is consistent with the actual model.

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An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

Natural Hazards and Earth System Science ◽

10.5194/nhess-14-2125-2014 ◽

2014 ◽

Vol 14 (8) ◽

pp. 2125-2132 ◽

Cited By ~ 18

Author(s):

F. H. An ◽

Y. P. Cheng

Keyword(s):

High Pressure ◽

Coal Seam ◽

Large Scale ◽

Underground Mines ◽

Low Permeability ◽

Gas Distribution ◽

Coal Gas ◽

Annular Zone ◽

Wall Deformation ◽

Coal And Gas Outbursts

Abstract. Large-scale coal and gas outbursts pose a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution, and the permeability is required to be several orders of magnitude less than that of normal coal and enough length is also in demand. A steep gradient of gas pressure in the low-permeability zone and the high-pressure gas in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high-pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

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An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-1-4751-2013 ◽

2013 ◽

Vol 1 (5) ◽

pp. 4751-4775 ◽

Cited By ~ 5

Author(s):

F. H. An ◽

Y. P. Cheng

Keyword(s):

Coal Seam ◽

Large Scale ◽

Gas Pressure ◽

Underground Mines ◽

Low Permeability ◽

Gas Distribution ◽

Coal Gas ◽

Annular Zone ◽

Wall Deformation ◽

Coal And Gas Outbursts

Abstract. Large-scale coal and gas outbursts post a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution. A steep gradient of gas pressure in the low-permeability zone and the high gas pressure in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

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Retraction Notice: Composite Advanced Detection for Coal Seam Thickness in Coal Roadway

The Open Petroleum Engineering Journal ◽

10.2174/1874834101609010324 ◽

2016 ◽

Vol 9 (1) ◽

pp. 324-324

Author(s):

Wang Bo ◽

Zhang Xiayang ◽

Liu Shengdong ◽

Lu Tuo ◽

Chen Mulan

Keyword(s):

Coal Seam ◽

Seam Thickness ◽

Coal Roadway ◽

Retraction Notice ◽

Coal Seam Thickness

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Research and application of coal and gas outburst early warning system based on gas geological features

E3S Web of Conferences ◽

10.1051/e3sconf/202132901086 ◽

2021 ◽

Vol 329 ◽

pp. 01086

Author(s):

Yunlong Zou

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Early Warning ◽

Early Warning System ◽

Coal Mines ◽

Warning System ◽

Geological Structure ◽

Gas Outburst ◽

Coal And Gas Outbursts ◽

Gas Disasters

The geological structure of coal mines has always been a dangerous object of attention in coal mine outburst prevention work. In order to realize coal mine safety information management and early warning of gas disasters, comprehensive use of gas geological theory, coal mine disaster warning theory, computer information technology and other analysis methods, considering the influence of geological structure, coal seam occurrence parameters, and gas parameters, an early warning indicator system for identifying the risk of coal and gas outbursts reflecting the geological characteristics of gas has been constructed. The coal and gas outburst risk identification and early warning system is constructed using the principle of multi-index step-by-step identification and extreme value determination, and it is applied on-site in the 3303 Measure Lane in the East Shaft Area of Sihe Mine. The research results show that the constructed early warning system can provide accurate early warning for the area (belt) affected by the geological structure by 10m, and can provide accurate early warning of coal and gas outbursts based on the outburst signs of gas geology such as the thickness of soft layers and changes in coal seam thickness. This technology provides effective support for coal mines to effectively prevent gas disasters and ensure coal mine production safety.

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Quantitative analysis of parameters' influence on the stability of coal roadway clamped by upper and lower soft rock with extra thickness

International Journal of Modeling Simulation and Scientific Computing ◽

10.1142/s1793962313500232 ◽

2014 ◽

Vol 05 (02) ◽

pp. 1350023

Author(s):

Zenghui Zhao ◽

Weiming Wang ◽

Jixing Yan

Keyword(s):

Quantitative Analysis ◽

Coal Seam ◽

Significant Influence ◽

Evaluation Method ◽

Soft Rock ◽

Mining Area ◽

Remarkable Effect ◽

Coal Roadway ◽

The Stability ◽

Rock Strata

In this paper, a physical model of coal roadway which is clamped by upper and lower soft rock with extra thickness was built according to the characteristics of soft rock strata in china's western mining area. Then, a series of orthogonal numerical experiments were carried out by selecting the strength and stiffness parameters of soft rock and coal seam as well as the in situ stress of soft rock strata as experimental factors and roadway displacements (convergence displacements of sides, displacement of roof to floor) as experimental indexes. By constructing the F statistics with different inspection levels, evaluation method for influence of the experimental factors on stability indexes were defined. Thus, influence degrees of specified parameters on the stability of roadway were divided into five classes as follows: highly significant influence, significant influence, relatively significant influence, little significant influence, and no influence respectively which realize the quantitative analysis of the influence degrees of experimental factors. The finite element calculation results showed that main failure mode of coal roadway that usually showed as tension failure of coal seam in roof and deformation factors of coal seam had the most remarkable effect on roadway displacements. The conclusions provide theoretical basis for further analysis of the mechanism of "roof burst" in roadway maintenance.

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