Non-harmonious deformation controlling of gob-side entry in thin coal seam under dynamic pressure

Fan, Kegong; Hong-guang, Liang; Ma, Chishuai; Zang, Chuanwei

doi:10.1016/j.jrmge.2014.05.001

Cited by 19 publications

(8 citation statements)

References 3 publications

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“…The high dynamic pressure often results in excessive entry deformation and convergence. The cutting cantilever beam theory [32] was proposed to determine the optimal gob-side entry location in GER and the reasonable rib pillar width in GED [9,12,13,16,17,21,23,31,33,34].…”

Section: Previous Studies On Gob-side Entriesmentioning

confidence: 99%

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A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems

et al. 2018

Energies

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Abstract:The gob-side entry layout is popular at two-entry longwall mine sites in China for the benefit of improving the coal recovery rate. Currently, two methods have been widely used to develop gob-side entries, including gob-side entry retaining and gob-side entry driving. Gob-side entry retaining maximizes the recovery rate by pillarless mining but increases the difficulty in gob-side entry support. Also, this method has limited applications in hard roof conditions. The gob-side entry driving mine site uses the rib pillar to separate the gob entry and the gob area of the previous panel, which leads to additional coal losses. The waste is more intolerable in large-cutting-height panels and longwall top coal caving panels as the Chinese government limits the minimum recovery rate of longwall panels using these mining methods. In this paper, a new gob-side entry layout method, termed gob-side pre-backfill driving, is established to overcome the shortcomings of the existing methods. The new method eliminates rib pillar losses and enhances gob-side entry stability. The feasibility of gob-side pre-backfill driving is studied by numerical modelling and a field trial at Changcun Mine in China. The results indicate that gob-side pre-backfill driving is an alternative for gob-side entry development. This method is practical and also has the potential to bring significant economic benefits to the mining industry.

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Section: Previous Studies On Gob-side Entriesmentioning

confidence: 99%

“…Figure 1. Two method being commonly used in the gob-side entry layout: (a) gob-side entry retaining (GER), revised by Feng and Zhang [9]; (b) gob-side entry driving (GED), revised by Fan et al [16]. …”

Section: Introductionmentioning

confidence: 99%

A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems

et al. 2018

Energies

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“…At the rear of the working face, the load of the supporting structure is related to the length of the suspended roof and the distribution state of cracks and changes sharply with the collapse of the roof. At the same time, it also bears the impact load caused by the collapse of the roof [ 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

A Field Study Implementing New Monitoring Technology for Roof Caving and Systematic Monitoring for Gob-Side Entry Retaining via Roof Cutting in Underground Coal Mining

Chen

Zhang

Cao

et al. 2023

Sensors

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The longwall mining method with gob-side entry retaining via roof cutting is a new underground coal mining method which has the characteristics of a high resource recovery ratio and environmental friendliness. Due to the complexity of this method, the research method of case-based dynamic on-site monitoring, analysis, adjustment, and optimization is usually adopted. Based on a roadway retaining via roof cutting project, in addition to the traditional indirect monitoring method of hydraulic support pressure, this study innovatively establishes a direct monitoring method for roof caving by monitoring the gangue pressure in the goaf, which provides data for the roof cutting effect and offers a new method for studying the overlying strata movement. In the project, a comprehensive monitoring and analysis system was established, including gangue pressure, cable bolt stress, bracket pressure, roadway deformation, and roof separation, which was used to dynamically analyze the effect of roof cutting and optimize the support design. The results show that the pressure of the hydraulic support close to the roof cutting is low, indicating that roof cutting is favorable in the roadway retaining mining method. The roadway deformation in the advanced abutment pressure area of the working face is small. The mining-induced stress caused by the collapse and compaction of the overlying strata in the goaf is the dominant factor affecting the effect of roadway retaining, especially in the 50–100 m range behind the working face, where the dynamic load causes high bearing capacity of the support elements, large roadway convergence, and roof separation. Temporary support and supplementary reinforcement should be added when necessary. The monitoring system presented in this study is highly comprehensive, simple, reliable, and low in cost, providing a reference for roof cutting roadway retaining projects and roof caving-related studies.

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“…In the GER and GED procedures, during the excavation and mining, the stability of the surrounding rock is affected by several factors (Han et al 2019;Jiang et al 2016;Liu et al 2009). Also, asymmetric deformations appear under dynamic conditions (Fan et al 2014). In the GER and GED procedures, the size of the coal pillar (or the width of the backfill wall) and the angle of the cantilevered roof block have a great influence on the stress distribution in the surrounding rock (Wu et al 2019;Zha et al 2017;Chang et al 2018;Feng and Wang 2020).…”

Section: Introductionmentioning

confidence: 99%

Stress and deformation analysis of gob-side pre-backfill driving procedure of longwall mining: a case study

Zhang

Kulatilake

et al. 2021

Int J Coal Sci Technol

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At present, non-pillar entry protection in longwall mining is mainly achieved through either the gob-side entry retaining (GER) procedure or the gob-side entry driving (GED) procedure. The GER procedure leads to difficulties in maintaining the roadway in mining both the previous and current panels. A narrow coal pillar about 5–7 m must be left in the GED procedure; therefore, it causes permanent loss of some coal. The gob-side pre-backfill driving (GPD) procedure effectively removes the wasting of coal resources that exists in the GED procedure and finds an alternative way to handle the roadway maintenance problem that exists in the GER procedure. The FLAC3D software was used to numerically investigate the stress and deformation distributions and failure of the rock mass surrounding the previous and current panel roadways during each stage of the GPD procedure which requires "twice excavation and mining". The results show that the stress distribution is slightly asymmetric around the previous panel roadway after the “primary excavation”. The stronger and stiffer backfill compared to the coal turned out to be the main bearing body of the previous panel roadway during the "primary mining". The highest vertical stresses of 32.6 and 23.1 MPa, compared to the in-situ stress of 10.5 MPa, appeared in the backfill wall and coal seam, respectively. After the "primary mining", the peak vertical stress under the coal seam at the floor level was slightly higher (18.1 MPa) than that under the backfill (17.8 MPa). After the "secondary excavation", the peak vertical stress under the coal seam at the floor level was slightly lower (18.7 MPa) than that under the backfill (19.8 MPa); the maximum floor heave and maximum roof sag of the current panel roadway were 252.9 and 322.1 mm, respectively. During the "secondary mining", the stress distribution in the rock mass surrounding the current panel roadway was mainly affected by the superposition of the front abutment pressure from the current panel and the side abutment pressure from the previous panel. The floor heave of the current panel roadway reached a maximum of 321.8 mm at 5 m ahead of the working face; the roof sag increased to 828.4 mm at the working face. The peak abutment pressure appeared alternately in the backfill and the coal seam during the whole procedure of "twice excavation and mining" of the GPD procedure. The backfill provided strong bearing capacity during all stages of the GPD procedure and exhibited reliable support for the roadway. The results provide scientific insight for engineering practice of the GPD procedure.

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Non-harmonious deformation controlling of gob-side entry in thin coal seam under dynamic pressure

Cited by 19 publications

References 3 publications

A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems

A New Gob-Side Entry Layout Method for Two-Entry Longwall Systems

A Field Study Implementing New Monitoring Technology for Roof Caving and Systematic Monitoring for Gob-Side Entry Retaining via Roof Cutting in Underground Coal Mining

Stress and deformation analysis of gob-side pre-backfill driving procedure of longwall mining: a case study

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