| Soft rock engineering as a worldwide problem was proposed as early as in the lastcentury60s. Especially in the coal mine safety construction and production, it plagued theenginner and technicist for a long time. Soft rock has some geologiccal features such asswelling, plasticity, dispersibility, disintegrative and rheological properties.The biggestproblem of soft rock tunnel in engineering practice is dfficult to support beacause of itshuge plastic deformation. In order to study the deformation failure mechanism and supportmethod of excavted soft rock tunnel, based on the exixting research results, finite elementnumerical simulation and field research are used to study and validate the combinedsupport system.The failure deformation characteristic and influencing factors of surrounding rock insoft rock tunnel are analyzed. Based on fileld observation and analysis of tunnelsurrounding rock lithology, the cause of large deformation in of roadway related toenginering geology conditon. Tunnel surrounding rock is easy bibulous deliquescence withobvious plasticity and dilatability because it contain too much aluminum and sandymudstone. The lower intensity of surrounding rock because of its plentiful stratificationmake the tunnel easier to buckling deformation.Based on the geological characteristic that loose, soft, break and smash of surroundingrock in NO.2conveyors tunnel, the rational support principle is proposed that is timelysupport and secondary support. The soft rock tunnel should be supported timely afterexcavation, because the strength of surrounding rock lose quickly for the influence ofweathering and water. The surface of surrounding rock is closed by shotcrete to prevent itsweathering deliquescence. The deformation of soft rock tunnel is so fast and huge that thesupport is very diffcult to suceess for one time. The first time support improve the residualstrength of surrounding rock, avoid excessive expansion deformation. The second time support is implemented after huge deformation finished, provide the ultimate strength andrigidity, guarantee the stabilityof the soft rock tunnel for a long time.The finite element software ANSYS is used to design the cross section of tunnel. It isanalyzed by contrast the stress, displacement and plastic zone of surrounding rock withdifferent support. The combined support, shotcreting and anchor suport, is proposed. Theresults of numerical simulation analysis shows that the support scheme satisfies thestability requirement of tunnel with soft surrounding rock. By means of comparativeanalysis between the fiedl monitoring results and numerical simulation results, it isconcluded that the deformation rule of soft surrounding rock between them is consistentbasicly. It shows that the combined support system by bolt, shotcrete and anchor cansignificantly increase the strength and ability to bear weight of soft surrounding rock,conform to the need of engineering practice. |
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