Stability analysis of integral load-bearing structure of surrounding rock of gob-side entry retention with flexible concrete formwork

Huang

Energy Science & Engineering

et al. 2021

Recently, concerns regarding coal resource waste and safety mining have grown worldwide. The no-pillar mining method without advance tunneling, known as the N00 longwall mining method, represents a rational alternative in this regard.Since the 20th century, coal mining technology has undergone long-term development in China. The mining methods used in China's coal industry can be classified into three types: longwall mining, gob-side entry retaining, and N00 longwall mining.The longwall mining method, which originated in Britain during the early 18th century, was first used in China in the 1930s and has been developed for approximately 90 years. It has become one of the landmark achievements in the field of coal mining in China. 1,2 However, a large coal pillar measuring 20-50 m and double advance tunneling roadways should be set up before stopping a working face when using this mining method. This results in low coal recovery rates and mining productivity. Hence, the contradiction between this mining method and China's energy characteristics has become more prominent.

mentioning

confidence: 99%

Validation study of no‐pillar mining method without advance tunneling: A case study of a mine in China

Huang

Energy Science & Engineering

et al. 2021

Energy Science & Engineering

“…where m is coal seam thickness, 5.40 m; A is lateral pressure coefficient, taken as 1.2; φ 0 is the internal friction angle of coal seam, 20°; c 0 is the cohesion, 0.6 MPa; k is stress concentration factor, taken as 1.5; γ is average bulk density of rock, 25 kN m −3 ; H is buried depth of coal seam, 630 m; p z is support resistance provided by bolt support to coal wall, 0.25 MPa. [30][31][32] According to the above conditions, X 1 = 3.03 m and X 2 = 1.45-2.42 m are obtained. Therefore, it can be concluded that reasonable range of coal pillar width B is 6.28-7.25 m.…”

Section: Theoretical Calculationmentioning

confidence: 99%

Determination of coal pillar width for gob‐side entry driving in isolated coal face and its control in deep soft‐broken coal seam: A case study

Wang

Xie

2022

Large deformation control of surrounding rock in deep soft-broken coal roadway has always been a key scientific and technological problem restricting the deep coal resources exploitation. Taking the gob-side entry driving (GED) in isolated coal face under deep soft-broken coal as research object, the prominent difficulties of surrounding rock control were clarified. Through numerical simulation, the evolution laws of deviatoric stress and plastic zone of GED under different coal pillar widths were studied. Combined with rational calculation, reasonable coal pillar width was determined to be 7.0 m. The study shows that severe disturbance distance in the front section of the coal face is 22 m, and makes it clear that coal pillar and roof are the key control areas. A subregional asymmetric combined support technology named anchor cable truss in roof and coal pillar + anchor cable in solid coal + single prop reinforced support in 25 m ahead of the coal face was proposed. The field application and ground pressure observation results show that good control effect has been achieved after adopting subregional asymmetric support technology under 7 m coal pillar width. The research results have important reference significance for safe mining in deep coal resources.

“…During the coal extraction process of longwall working face, with the advancement of the longwall working face, the immediate roof above the coal seam will sink, displace, break, and collapse, but the main roof above the coal seam will break to form an arc-shaped triangle block (Zhang et al, 2020a;Shen et al, 2021). There has been an amount of research on gob-side entry driving, gob-side entry retaining, and other no-pillar layout systems (Shen et al, 2018;Xie et al, 2020;Zhang et al, 2021b). Hou and Li (2001) explained the "small structure" of the roof in detail, and provided the layout position of the narrow coal pillar roadway.…”

Section: Introductionmentioning

confidence: 99%

Study on the Stability of Coal Pillars Under the Disturbance of Repeated Mining in a Double-Roadway Layout System

et al. 2021

The double-roadway layout system, which is extensively applied in large mines, has the potential to significantly balance excavation-mining and improve mine ventilation and transportation capacity. However, the coal pillar in the double-roadway layout system is easily destabilized due to the disturbance of repeated mining, which has a significant impact on the safety and reliability of coal mines. This paper takes the coal pillar and its supporting structure of the double-roadway layout system as the research object, establishes a UDEC trigon numerical calculation model, and systematically corrects the input parameters, while explaining the excavation method of roadways and the simulation method of the supporting structure element. The numerical simulation results show that under the conventional support intensity conditions, the internal damage of the coal pillar during the excavation period is about 20%, while the internal damage to the coal pillar develops to 55% throughout the first-panel mining. During the disturbance of repeated mining, the damage in the coal pillar increased to 90%, and the coal pillar was already in a state of failure. Under the combined control of rock bolts and counter-pulled anchor cables, the coal pillar damage does not change significantly during the excavation and first-panel mining. During the disturbance of repeated mining, the damage of the coal pillar is reduced to 63%. There is a certain low damage area in the coal pillar, which can ensure the stability of the coal pillar and its supporting structure as a whole. Furthermore, the on-site monitoring results show that the maximum value of the floor-to-roof and rib-to-rib convergence of a W1310 tailgate during the repeated mining disturbance stage is 730 and 620 mm, respectively. The findings of this study give an approach to—as well as estimated values for the design of, including its “small structure” control technical parameters—the double-roadway layout system.