Research On The Effect Of Long Prestressed Anchor Cable To Control The Large Deformation Of Maoyu Mountain Tunnel

Maoyu mountain tunnel is a soft rock and deep buried tunnel, with in high geostressenvironment. And loose circle range is large, so ordinary anchor length is not enough to passthough loosened zone anchorage to the stable rock mass, that makes the traditional shotcretecannot fully play its role, and construction progress is seriously affected as well as there is abig security hidden danger. According to the above characteristics, choose long prestressedanchor cable with rockbolt concrete supporting structure to test the improvement of largedeformation condition.The research is based on the background of the long prestressed anchor cable test thesection of Maoyu mountain tunnel of Lanzhou-Chongqing railway; expand the followingresearch on the control of large deformation.(1) From12m and18m long anchor cable test sections of the tunnel each choose amonitoring section as the research object, respectively from the deformation of surroundingrock, surrounding rock pressure, the contact pressure and anchor force four aspects, to analyzeand summarize the deformation of surrounding rock stress and strain, as well as secondarylining stress distribution.(2) Using the FLAC3Dsoftware to simulated the tunnel construction process in12m and18m long cable test section, and the12m long cable layout in the location of the18m longanchor position, analysis the tunnel deformation and stress of surrounding rock and the law ofthe contact pressure changing with the construction space..(3) Comparing the actual measured value of the deformation and stress of surroundingrock and initial support and secondary lining contact pressure of MaoYu mountain tunnel ofprestressed anchor cable test section with the numerical simulation results of the comparativeanalysis, comprehensive selection of deformation control effect, to select the optimal anchorapplied scheme.The main research results:(1) The long prestressed anchor cable is a kind of "active" support form, easier to controlthe deformation of surrounding rock, and the12m and18m cable length can be throughabout6m the surrounding rock loose area, anchoring the loose rock surface to deep thestability of the undisturbed rock mass, making full use of the undisturbed body stability of thereinforced tunnel caverns(2) Through analyzing the actual measured value of surrounding rock displacement andstress, it is concluded that the rule of deformation and stress of the tunnel test section longprestressed anchor cable. The measured value of each measuring point of displacement andstress of surrounding rock, as well as the contact pressure in the tunnel, is greatly influenced by tunnel three steps of the construction process, the influence of volatility for a long time,and increase its period is longer, the cumulative amount is large, as well as both side appearasymmetric conditions. The vault accumulated settlement amout of the monitoring section of12m long anchor cable test section was371mm, and the convergence value of top steps was438mm, the convergence value of middle steps was347mm, the convergence value of lowersteps was269mm; the vault accumulated settlement amout of the monitoring section of18mlong anchor cable test section was296mm, and the convergence value of top steps was387mm, the convergence value of middle steps was340mm, the convergence value of lowersteps was279mm. While after prestressed anchor applied, the parts of deformation controleffect is obvious, which can effectively reduce the stress of the second lining.(3) According to the12m and18m two long cable test section and changing layoutlocation section of the three-dimensional numerical simulation analysis, the convergencevalue of middle and down steps of the12m long anchor cable test section of the supportingstructure decreases about30%than the18m long cable test section; the vault settlement ofthe18m long anchor cable test section decreases about15%than the12m long cable testsection, and decreases about20%in the top steps convergence controlling; the vaultsettlement of changing layout location section is less about5%than the18m long cable testsection. The18m long cable test section on deformation of arch department, the surroundingrock pressure and contact pressure has a better control, the changing layout location sectionhas a slightly worse control effect; the12m long cable test section of the supporting structureof wall range has better control effect.