An Innovative Approach for Gob-Side Entry Retaining in Thick Coal Seam Longwall Mining

He, Manchao; Gao, Yubing; Yang, Jun; Gong, Weili

doi:10.3390/en10111785

Cited by 120 publications

(90 citation statements)

References 22 publications

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“…Currently, some scholars have built structural mechanical models [53][54][55][56] for roof cutting, such as the transfer rock beam mechanical model [53], mechanical model of fracturing roofs to maintain entry approach [54], dynamic pressure area mechanical model [55], and main roof breaking upon retracement channel mechanical model [56]. These mechanical models revealed the role of various supporting structures, such as roadside backfill and coal support, and the basic characteristics of the main roof movement in GER.…”

Section: Discussionmentioning

confidence: 99%

“…Assuming that the bearing force of the gangues on the roof has a linear distribution, according to the rock dilatancy [52][53][54][55], the supporting resistance of the gangues in goaf for non-roof-cutting F G1 is as follows.…”

Section: Roadside Prop Stressmentioning

confidence: 99%

“…This will not only cause accidents such as supporting failure and rib spalling in deep mining conditions, but also increase the supporting cost and workload, affect the mining progress and continuity. Therefore, the technique of no-pillar mining with automatically formed GER was proposed [53][54][55][56][57][58]. The roof was presplit along the gob side by borehole blasting, the gob-side roof was cut down, and the goaf was filled owing to the working face advanced, which based on "roof-cutting short cantilever beam" theory.…”

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confidence: 99%

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Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

et al. 2019

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Roof cutting is an effective technique for controlling the deformation and failure of the surrounding rock in deep gob-side entry. The determination of the roof cutting parameters has become a popular research subject. Initially, two mechanical models are established for the non-roof-cutting and roof-cutting of gob-side entry in deep mining conditions. On this basis, the necessity and significance of roof cutting is revealed by analysing the stress and displacement of roadside prop. The Universal Distinct Element Code numerical simulation model is established to determine the key roof-cutting parameters (cutting angle and cutting height) according to the on-site situation of No. 2415 headentry of the Suncun coal mine, China. The numerical simulation results show that with the cutting angle and height increase, the vertical stress and horizontal displacement of the coal wall first increase and then decrease, as in the case of the vertical stress and displacement of roadside prop. Therefore, the optimum roof cutting parameters are determined as a cutting angle of 70 • and cutting height of 8 m. Finally, a field application was performed at the No. 2415 headentry of the Suncun coal mine. In situ investigations show that after 10 m lagged the working face, the stress and displacement of roadside prop are obviously reduced with the hanging roof smoothly cut down, and they are stable at 19 MPa and 145 mm at 32 m behind the working face, respectively. This indicates that the stability of the surrounding rock was effectively controlled. This research demonstrates that the key parameters determined through a numerical simulation satisfactorily meet the production requirements and provide a reference for ensuring safe production in deep mining conditions. about 100-500 m, the microstructures, basic mechanical characteristics, and engineering responses of coal and rock have changed significantly in response to the "three highs and one disturbance" environment [10][11][12][13]. The main features are that the surrounding rock has a large deformation, high deformation speed, long deformation duration, and rheological characteristics. Hence, maintenance of the gob-side entry becomes extremely difficult, and large deformation and failure accidents occur occasionally [14][15][16][17][18].Many theoretical studies and field practices on GER technology under deep mining conditions have been completed, and three major advancements should be considered. First, the surrounding rock deformation characteristics and failure evolution law of deep GER are revealed under various geological conditions [19][20][21][22][23]. The roof of the gob-side entry is simplified into a rectangular "superposed stratified plate" structure [24,25], and the concept of the strip segmentation method for the roof load is proposed according to the theory of elastoplastic mechanics. On this basis, used a numerical analysis method to identify the influence mechanism of the roof fracture location, roof rotation, and long-term creep of the surrounding rock in deep ...

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Section: Discussionmentioning

confidence: 99%

Section: Roadside Prop Stressmentioning

confidence: 99%

mentioning

confidence: 99%

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Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

et al. 2019

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“…Compared with GER, this mining technology has more prominent advantages, such as reducing the cost of mining, weakening the local stress concentration in roadway surrounding rocks, and preventing uneven settlement of the earth's surface. When the working face (F1) is mined with GERRC, the roadway R1 is not excavated ahead of the working face but is formed and retained behind the working face by using technologies including directional roof cutting, support with constant resistance large deformation cable (CRLDC), temporary support, and a series of equipment [20][21][22][23]. After F1 is finished, the recovery equipment can be immediately moved to F2 using shield haulers.…”

Section: Technical Principle Of Gerrcmentioning

confidence: 99%

Roof Deformation Characteristics and Preventive Techniques Using a Novel Non-Pillar Mining Method of Gob-Side Entry Retaining by Roof Cutting

et al. 2018

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Abstract:A new non-pillar mining technology, gob-side entry retaining by roof cutting (GERRC), different from the conventional gob-side entry retaining formed by a roadside filling support, is introduced in this study. In the new technology, roof cutting is conducted so that the roof plate forms a short cantilever beam structure within a certain range above the retained entry, thus changing the stress boundary condition of the roof structure. To explore the deformation characteristics of the roof under this special condition, a short cantilever beam mechanical model was established and solved using energy theory and displacement variational methods. Meanwhile, a theoretical and analytical control solution for roof deformation was obtained and verified via field-measured results. Based on the aforementioned calculation, the relationship between the roof deformation and main influence parameters was explored. It was concluded that the rotation of the upper main roof and width of the retained entry had the most significant impacts on roof deformation. Bolt and cable support and temporary support in the entry had a non-obvious influence on the roof deformation and could not prevent the given deformation that was caused by the rotation of the upper main roof. Based on comprehensive theoretical analysis and calculation results, ideas and countermeasures to control short cantilever roof deformation-that is, designing a reasonable height of roof cutting and a controlled width of retaining entry-were proposed and tested. Field monitoring shows that the entry control effects were satisfactory.

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“…The width of the wide pillar is 20-50 m. 10 It guarantees the stability of the GSE during the mining of thin, medium, and normal coal seams. [11][12][13] However, the abutment stresses of extra-thick coal seams are large and their influence ranges are wide. 14 Thus, the applicability of wide pillars in extrathick coal seams must be further studied.…”

Section: Introductionmentioning

confidence: 99%

Field and simulation study of the rational coal pillar width in extra‐thick coal seams

Zhao

2019

Energy Science & Engineering

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The principles of mining pressure in extra‐thick coal seams are different from those of medium‐thick and thick coal seams. Field investigation, laboratory test, and simulation analysis methods were used to study the correlation between the gob‐side entry (GSE) stability and coal pillar width during longwall top coal caving mining in extra‐thick coal seams. The test site is in Datong City, Shanxi Province, China. The mining pressure in N5209 tailgate with coal pillar of 30 m is severe based on the field investigations during the N5209 panel retreat. Global constitutive double‐yield and strain‐softening models were built to study the abutment pressures and plastic failure ranges of coal seams with different thicknesses and coal pillar widths. The simulation results show that the GSE with an 8‐m coal pillar is destressed and minimal GSE deformation occurs. In addition, the abutment stress in the coal pillar decreases with increasing coal seam thickness. The field tests indicate that the GSE with an 8‐m‐wide coal pillar is stable in extra‐thick coal seams. This study provides a reference for the coal pillar design in coal mines with similar geological and mining conditions.

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An Innovative Approach for Gob-Side Entry Retaining in Thick Coal Seam Longwall Mining

Cited by 120 publications

References 22 publications

Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

Roof Deformation Characteristics and Preventive Techniques Using a Novel Non-Pillar Mining Method of Gob-Side Entry Retaining by Roof Cutting

Field and simulation study of the rational coal pillar width in extra‐thick coal seams

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