Study Of Failure Mechanism And Supporting Technology On The Deep Roadway At Qujiang Colliery

The research relies on the project of “The Support of Deep, Thick Composite Roof CoalRoadway and Soft Rock Roadway”. The combined support is proposed based on the failuremechanism of Qujiang Coal mine’s roadway full analyzed. The application of fractional stepand combined support in the field to take a good effect.By laboratory experiments and field analysis, it is concluded that the creep of roadwaysurrounding in high stress and the unreasonable supporting are the main reasons of supportfailure in Qujiang Coal. The low strength of surrounding, lithologic difference, constructionquality of bolt is poor and the floor rock strength weaken by water are the important reasonsfor roadway instability. In addition, roadway molding is irregular, roadway floor reworkedconstantly and vibration by shooting affect the stability of the roadway to a certain extent. Thestress in roadway surrounding is analyzed. By lsqcurvefit function, the monitoring data ofroadway deformation conducted least squares fit based on the rheological theory, whichdefined the secondary supporting opportunity of anchor cable. The superiority of fractionalstep and combined support fully discussed.By the FLAC3D software, the anchor cable parameters (strength, length, preload)analyzed based on orthogonal experiment. It is concluded that the influence of anchor cablepreload on roadway’s stability is largest; the influence of anchor cable length is second; theinfluence of anchor cable strength is smallest. With the inner boundary position of outerbearing structure changes to surrounding rock depth, plastic zone size and the maximumsubsidence of roof are increased. There is a reasonable anchor cable strength which caninhibit the deformation of the surrounding rock and achieve economic rationality. The optimalscheme which shows as A3B2C2(the strength of anchor cable, length, preload is19mm,6m,100KN respectively) is obtained at last.By FLAC3D software, numerical simulations of four different support programs on eastmain entry are conducted. It is concluded that the supporting effect of3,4scheme whichtakes anchor and grouting support are better than1,2scheme’s and in the role of anchor andgrouting, floor-heave is controlled on a large degree. Deformation of the surrounding rockwhich exist minor differences can be well controlled in the condition of3,4scheme. But fromcontour maps of vertical displacement, only the shallow strata of floor move up in thecondition of fractional step and combined support. In addition, force performance of roadwayupper arch is better than floor rectangular structure is a reason for roof subsidence smallerthan floor-heave.Fractional step and combined support used in engineering practice and the surface anddeep surrounding rock deformation of roadway are monitored and analyzed. It is concludedthat compared with shotcrete support, surrounding rock deformation is relatively small andgradually stabilized in experimental roadway. Compared with U-shaped bracket support (secondary support), the floor-heave significantly is smaller in experimental roadway. Thesurface surrounding rock deformation is caused by the deformation of the surface to1.5mdeep in surrounding of roadway, and the deep surrounding rock is not damaged inexperimental roadway. The practice shows that good supporting effect is get in the technologyof fractional step and combined support and the long-term stability of east main entry’ssurrounding rock in Qujiang mine is realized.