1、翻 译 部 分英语原文Stability and deformation of surrounding rock in pillarless gob-side entry retainingZhang Nonga,Yuan Liangb,Han Changlianga,Xue Junhuab,Kan Jiaguanga(a School of Mines, State Key Laboratory of Coal Resource and Mine Safety, China University of Mining and Technology,China;b National Engine
2、ering Research Center for Coal Gas Control,China)Abstract:We analyzed the stability of the retained gob-side entry in four different Chinese coal mining sites and evaluated the influencing factors of roadway deformation such as mining depth, support strength and area of gob-side hanging roof. It was
3、 found that the length of cantilever roof block above roadway has a major impact on the deformation, whereas the impact of mining depth is minor if the depth is less than 500 m. Minimum support resistance of 0.3 MPa is essential to effectively confine the deformation of a retained roadway. We perfor
4、med physical experiments to further study the features of roof fracturing and their impact on roadway deformation under three typical immediate roof conditions, i.e., thick-immediate roof, thin-immediate roof and non-immediate roof. In addition, equations to calculate desired support resistance of f
5、illed gob-side wall were derived based on superimposed continuous laminate model. The results provide valuable theoretical and practical guidance for implementing pillarless gob-side entry retaining in engineering practices.Keywords:Gob-side entry retaining; Surrounding rock; Structural stability co
6、ndition; Deformation impact factor1. IntroductionGob-side entry retaining refers to maintaining either a main-gate or tailgate behind mining face by constructing a fill-in sidewall on gob-side with special support to be reused for the next panel. Pillarless gob-side entry retaining can effectively i
7、ncrease coal recovery, reduce roadway development, and mitigate outburst risk. Since the 1950s, pillarless roadway has been practiced worldwide and extensive research has been carried out on support resistance, stability control principles and related technologies. Since 2005, gob-side entry retaini
8、ng has been further developed as a key technology for integrated coal production and methane extraction in China, which serves an important role in providing safe and longterm room for drilling and maintaining gas drainage boreholes. Nowadays, this coal extraction method has become a safe and effici
9、ent approach for mining gassy coal seams.The gob-side retained roadway has quite special deformation characteristics due to its special roof structure and stress change. The dynamic pressure loaded to a retained roadway is much higher than the abutment pressure ahead of mining face. This high dynami
10、c pressure often results in excessive roadway deformation and rapid shrinkage. As the mining depth increases, maintaining a pillarless gob-side roadway becomes more and more difficult. Therefore it is crucial to clearly define the impact factors of deformation and the structural stability conditions
11、 of retained roadway to meet the requirement of complex mining environments.2. Typical geological conditions and engineering results2.1. Engineering and geological conditionsFour cases in different mining areas of China were selected here for comparison. These geological conditions are very represen
12、tative and common in China. Detailed information is shown in Table 1.Table 1 Engineering and geological conditions of the four selected casesPanelsE1403 of Tiefa12418 of Huainan154307 of Jincheng1205 of FenxiFace width (m)220200180180Mining depth (m)405638200406Coalseam dip ()313.6612Coal thickness
13、(m)2.13.12.21.8Coal stiffnessf = 1.5f 1f = 2.2f2Main roofSandstone,5.9m thickSandstone,partly mingled with carbonaceous mudstone, 5.85 m thickLimestone, unique quality and density, UCS 116 MPa, 9.1 m thickCompound roof, no stable layerImmediate roofMudstone, 4m thickMudstone, 4.65 m thickMudstone, 1
14、.1m thickImmediate floorSiltstone,3.4m thickMudstone, 4.45 m thickMudstone, 8 m thickSandy shale, 1.53 m thickSurrounding faultsOne small faultSeventeen faults, including two large faults with more than 2 m throw.Three to four smallfaultsThree small faults2.2. Section shape and supporting strength o
15、f retained gob-side entryMaintenance of a retained gob-side entry subjected to strong mining influence is difficult. Incompatible deformation often occurs, which can lead to roof separation, sidewall convergence, and eventual failure of surrounding rock. Field tests showed that passive shed support,
16、 such as contractible U-shaped steel support, does not work under strong mining influence.The support resistance of the prop can be obviously improved only when the surrounding rock deformation fully fills up the space behind the support. However, it was observed that incompatible deformation often makes the prop turn pointed, flat or
