| With the increase of roadway section, support of gateroads for fully mechanizedcaving faces become difficult increasingly. The problem of supporting is prettyserious especially under the impact of plane of weakness. It is difficult to meet theneed from supporting of large-section gateroads for fully mechanized caving faces byutilizing existing theories and techniques of supporting. Based on the analysis of lawof distribution for deep tectonic stress in Juye coalfield, the thesis performs asystematical research on the mechanism of failure and control techniques forlarge-section gateroads for fully mechanized caving faces by using theoreticalanalysis, numerical calculation, field test and other means synthetically. The mainfindings are:（1）Analytic solutions for stress field of rectangular roadway are got by usingcomplex variable. The effect on stress field of rectangular roadway from aspect ratio,buried depth and coefficient of horizontal pressure under confining pressure of highlevel and low level are investigated. Based on these laws, criterion for large section isput forward.（2）Mechanism of interaction between width of roadway and plane of weaknessas well as law of influence on modes of roof failure from width of roadway areanalyzed through numerical calculation. Mechanism of roof failure for large-sectiongateroads for fully mechanized caving faces is revealed. With the growth of width ofroadway, horizontal displacement in surrounding rocks also increases constantly.Shear failure in surrounding rocks around plane of weakness become increasinglyserious, which would contribute to bed separation. Roof subsidence increasescontinuously, as well as subsidence speed. Modes of failure in fallow surroundingrocks transform from shear failure or combination of tensile and shear failure totensile failure. The width and scope of tensile failure goes up gradually with itsstability decreasing dramatically. Bed separation and deformation would occur whenthe tensile stress resulting from bed separation and deformation outnumbers tensilestrength of roof.（3）Mechanical model of supporting beam with elastic build-in on both sides isestablished. The position of build-on and distribution of normal stress on contactsurface are achieved with the consideration of the effect of damage. Relationshipbetween stability of roadway roof and width of roadway is got on the basis of criterion for large section. These theories are applied in headentry of7105working face inWangzhuang coal mine. The width of section-large gateroads for fully mechanizedcaving faces is determined to4.728m. When the width of roadway exceeds4.728m,depth of tensile failure outnumbers the thickness of anchorage zone. In this case, it isdifficult to maintain the roadway which can be defined as large-section roadway.（4）Position of the plane of weakness determines the stress state of the roof oflarge-section gateroads for fully mechanized caving faces. When plane of weaknessexists in the sides of the roof, right above the roof or the middle and fallow part ofroof, the roof of large-section gateroads for fully mechanized caving faces locates inhigh-level shear displacement zone, shear slump bed separation zone and tensiledamage zone respectively. In allusion to the mechanism of the three modes of failure,surrounding rocks control techniques named “intensive and hierarchical anchorsupporting for critical parts of three zones†is put forward.（5）In allusion to large-section gateroads whose width and buried depth are5.5m and400m respectively for fully mechanized caving face in Wangzhuang coalmine, field test was performed in headentry and open-off cut for7105working faceby using surrounding rocks control techniques for large-section gateroads. Field testsuggested that surrounding rocks control techniques named “intensive andhierarchical anchor supporting for critical parts of three zones†controlled thedeformation of surrounding rocks effectively and achieved the stability of surroundingrocks and supporting structure. |
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