Research On Principle Of Canceling The Inverted Arch Of Highway Tunnel Based On Fluid-solid Coupling

As an important building of tunnel lining structure，the arch plays an importantrole in the tunnel engineering．Inverted arch can improve the stability of the wholetunnel，strengthen the overall stiffness of supporting structure and inhibit the excessivedeformation of surrounding rock．The setting of tunnel inverted arch also caneffectively reduce the probability of tunnel disease．Highway tunnel design standardJTG D70-2004stipulates that tunnel should be set with inverted arch in the low levelof surrounding rock．The lot with Ⅳ，Ⅴ level surrounding rock needs to design theinverted arch，when the engineering analogy method is used to design composite lining;Three lane road tunnel in the lot with Ⅲ，Ⅳ，Ⅴ level needs to design invertedarch．Under what conditions of surrounding rock，but need to set the inverted archtunnel sPan under the condition of the highway tunnel specification does not give cleartheory basis． The standard doesn’t give Clear theory basis that what kind ofsurrounding rock conditions and tunnel sPan conditions need design invertedarch．There is a little study of the highway tunnel inverted arch under the condition oflow surrounding rock on its set and Parameters．Considering the role of the invertedarch，the relevant standards and economic benefits，study of the surrounding rocktunnel with low level on canceling the inverted arch principle is Particularlyimportant．Based on the fluid-structure interaction theory，this Paper relied on the ChongqingNanshan tunnel engineering uses large-scale finite element software ANSYS tosimulate the tunnel excavation process according to the actual geological condition ofthe tunnel with Ⅳ level surrounding rock，cross section form，supporting Parameters，excavation step sequence and ground water and the following three contents areanalyzed：（1）Aiming at the case that Nanshan tunnel with Ⅳlevel surrounding rockcancels inverted arch，the finite element software ANSYS is used to simulate theexcavation process．Respectively considering the stress field and the coupling ofseePage field-stress field， Ⅳlevel surrounding rock strength is reduced and thestrength Parameters of the inverted arch tunnel structure damage are got based on thetunnel stability criterion considering the combine of ANSYS calculationmisconvergence and tunnel structure characteristics’ displacement mutation．The general principles of canceling inverted arch in Nanshan tunnel with Ⅳlevelsurrounding rock section are got．Through the contrast analysis of finite elementcalculation results and field monitoring measurement data，the rationality of the finiteelement calculation results are examined．（2）Assuming that the tunnel with Ⅲ，Ⅳ surrounding rock does not set theinverted arch with different sPans，different working conditions are established using finite element method．The mechanics behaviors of tunnel with no inverted arch inexcavation process are analyzed with different sPan conditions． The safetyperformance of the tunnel with Ⅲ，Ⅳ surrounding rock is evaluated with differentsPans based on analyses．The feasibility of the grouting bolt instead of inverted archmeasures is analyzed．（3）assuming taking different inverted arch design Parameters applying to thetunnel with Ⅳ surrounding rock，different working conditions are established usingfinite element method based on Nanshan tunnel engineering．The tunnel structure’smechanical properties of every construction sequence step are analyzed with differentworking conditions．The reasonable Parameters of inverted arch the tunnel with Ⅳsurrounding rock and two lanes are got．...