Study of a no-pillar mining technique with automatically formed gob-side entry retaining for longwall mining in coal mines

Due to the complex geostress and mining conditions in the coal seam with depth of 800 m, stability of surrounding rock for gob‐side entry retaining is very difficult to achieve. In this paper, we firstly propose an innovative bolt‐grouting controlled roof‐cutting for gob‐side entry retaining (BCR‐GER) approach for deep coal mines. Secondly, a mechanical model of “surrounding rock‐supporting body” for BCR‐GER is constructed, which consists of coal wall, roadside props, and gangues in gob (the whole supporting body). Thirdly, the key parameters (ie, cutting height, cutting angle, grouting cable length, and row of roadside props) are designed. Finally, field practice was applied at the No. 31120 haulage roadway of the Suncun coal mine in China, and in situ investigations were conducted for verification. Field measurement results show that maximum convergences of roof‐to‐floor and side‐to‐side were 264 mm and 113 mm, respectively. What is more, the maximum support resistance of roadside props was reduced by approximately 58%. The deformation and failure of surrounding rock were effectively controlled, and the pressure on roadside props was greatly reduced. This research fully considers the bearing properties of gangues in gob, eliminates the secondary disasters caused by borehole blasting, and provides guidance and reference for deep surrounding rock control of the same or similar gob‐side entry.

“…According to rock dilatancy, we assume that the collapsed gangues fill the gob. So the length of gangue in gob after roof‐cutting is L G2 .

L_{G 2} = L_{E} italiccos θ - L_{0} - L_{R}

…”

Section: Mechanical Analysis and Key Parameters Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An innovative approach for gob‐side entry retaining in deep coal mines: A case study

Fan

Liu

Tan

et al. 2019

“…The cutting roof and release pressure technology was proposed by Academician He Manchao in 2008 . The working principle of the technology is as follows: When the working face is recovered, the inner surface and the side of the gob are supported by the constant‐resistance and large‐deformation anchor cable, and the working face is advanced by a certain distance.…”

Section: Principle Of the Cutting Roof And Release Pressure Mining Tementioning

confidence: 99%

Evolution and application of airflow permeability characteristics of gob in roof cutting and pressure releasing mining method

Chen

Wang

et al. 2020

Cutting roof and release pressure technology has changed the pressure transmission mode of the roof and the caving characteristics of roof rock, which in turn has changed the permeability evolution of the gob. To obtain the permeability characteristics of the gob for the roof cutting and pressure releasing mining method, a mathematical model for the gob voidage and permeability was established by analyzing the overlying strata movement law and the lateral stress variation in the gob. The airflow migration law of haulage roadway 12 201 in Halagou coal mine was studied using Fluent software and an established mathematical model. The main conclusions obtained are as follows: The overburden pressure and lateral stress in the gob gradually increase with the advancement of the working face; along the direction of the retaining roadway, there are two roadway windflows entering the critical zones (the 22-100 m and 390-398 m sections). The inflow at these two sections accounted for 59% of the total air inflow, of which the most critical is the 28-53 m section, which accounts for 43% of the total air inflow in the two severe air leakage sections. The findings of this work provide a theoretical basis for the implementation of antileakage technology in the gob under the roof cutting and pressure releasing mining method and help reduce the risk of spontaneous combustion in the gob. K E Y W O R D Scaving characteristics of roof rock, cutting roof and release pressure, gob, voidage and permeability model 2074 |

“…The strata in the lower part of the fracture zone fractured into beams near the face end of the longwall face. One end of the rock beam fractured above the coal body and was supported by the coal body and the immediate roof, whereas the other end was supported by the caved stones in the goaf . A “fractured arch” was composed of positions at the end of each fractured strata in the fractured zone …”

Section: Failure Mechanism Of the Gateroad Systemmentioning

confidence: 99%

Field and numerical investigations of gateroad system failure under an irregular residual coal pillar in close‐distance coal seams

Shang

Ning

et al. 2019

The Gaojialiang Coal Mine in Inner Mongolia in China was used as an example to investigate the process of chain pillar and gateroad failure in the lower coal seam under the effect of an irregular residual coal pillar in the upper close‐distance coal seam. The results indicated that after the longwall face in the lower coal seam retreated through the area under the large irregular residual coal pillar in the upper coal seam, the bearing area of the residual coal pillar decreased and the roof pressure continuously concentrated in the elastic core area of the residual coal pillar. Isolated triangular slab rock was formed above the triangular residual coal pillar, and the weight of the overlying strata was transferred downward through the triangular slab rock. When the chain pillar under the residual coal pillar was destroyed due to loading that exceeded its carrying capacity, the upper triangular slab rock rotated and sank, which resulted in the intensification of the concentrated stress in the solid rib of the gateroad in the lower coal seam. Based on the analysis, it is suggested that in the design of a longwall system, a gateroad under an isolated residual coal pillar in the upper coal seam should be avoided when mining in close‐distance coal seams.