Gas Distribution Law for the Fully Mechanized Top‐Coal Caving Face in a Gassy Extra‐Thick Coal Seam

Abstract

Mine gas overflow is a serious threat to the safe and efficient longwall mining of gassy coal seams. Based on the field mining conditions and gas extraction of the fully mechanized top-coal caving face of a gassy coal mine, the space volume fraction distribution and emission (extraction rate) of gas in the face were tested by an arrangement of measuring points in the stereo grid. The isograms of gas volume fraction distribution for each measurement section and air direction in the face are drawn. The research shows that each measurement section gas volume fraction distribution is presented for an asymmetric concave curve along the vertical direction of the coal wall in the air-inlet side and the air-return side of the face; on the working face air-return side, the determination of gas volume fraction distribution of the section appears as falling straight line along the vertical direction of the coal wall. Before the first weighting, the absolute quantity of gas emission in the working face increased with the advancing of the working face, reached the maximum at the time of the first weighting, and then remained stable.

The Innovative Design of Deep In Situ Pressure Retained Coring Based on Magnetic Field Trigger Controller

“…Such a device can be used for pressure-retaining coring of a target formation in any direction in coal mines, shale gas fields, and other fields. is device provides in situ cores for the study of coal seam gas distribution, deep rock burst tendency, and destructive evaluation [42,43]. e feasibility of this innovative design is verified through the preliminary exploration of the magnetic field space, and the optimal magnetic circuit design is obtained, which provides data support and a theoretical basis for the study of the magnetic field self-triggered pressureretaining controller.…”

Research on Directional Controllability of Cracking in Hydraulic Fracturing of Hard Overburden Based on Local Stress Field Intervention

“…This part of coal pillar is affected by the goaf of the old kiln, and the whole coal pillar is in a plastic state, with low bearing capacity and a width of x 1 . 2 Area II: the isolated bearing area. This part of the coal pillar is less affected by disturbance, and the whole part is in an elastic state, with strong stability, good bearing capacity, and almost no damage, which can well isolate the gas and water in the goaf of the old kiln; its width is x 2 .…”

“…It can be seen from Figure 5: 1 When the width of the coal pillar in the roadway protection changes, the stress on the working face and the goaf has little influence, and the stress value is basically stable at 2~4 MPa; the internal stress of the coal pillar is obviously affected, and every change in coal pillar width can cause the internal stress to change by 2~5 MPa. 2 With the increase in coal pillar width, the stress peak area gradually shifts from the middle of the coal pillar to the goaf side, the stress concentration range gradually decreases, and the stability of the coal pillar gradually improves.…”

“…The increase in the mining of coal resources brings rising tensions to the Chinese resource situation. The roadway protection technology regarding small coal pillars in gobside entry driving has been gradually adopted by more and more mines, with the width of coal pillars reduced from the original 30~40 m to 5~8 m, which not only greatly improves the coal recovery rate, but also prevents the stress outburst caused by the traditional wide coal pillars [1][2][3][4]. However, various types of problems caused by small coal pillar mines under the condition of a hard roof are becoming more and more serious due to the large internal bearing deformation of small coal pillars, the run-through of the plastic zone, and the poor isolation effect caused by the long hanging hard roof, leading to secondary disasters, such as harmful gas leakage in the goaf [5][6][7][8].…”

The Key Stratum Structure Morphology of Longwall Mechanized Top Coal Caving Mining in Extra‐Thick Coal Seams: A Typical Case Study

“…Wang et al [15] studied the relationship between horizontal section mining and rock burst under conditions of steeply inclined and extra-thick coal seam and put forward reasonable measures to prevent rock burst. Based on the specific geological conditions, Wang et al [16] explored the distribution and emission law of gas in extra-thick coal seams. Wang et al [17] investigated key mining technologies and equipment of LMTCCM in extra-thick coal seams and successfully applied to Tashan coal mine.…”