The Construction Numerical Simulation And Stability Analysis For Ganshan Tunnel Of Tianping Railway

In this paper, the Guanshan special long tunnel that belong to the new railway Tianshui to Pingliang as the engineering background, combined with the research results in the field of deep buried long tunnel at home and abroad recently, using ANSYS general-purpose finite element software, complete numerical analysis on the whole contraction process of Guanshan tunnel, start from the quantitative evaluation of the impact for stability of surrounding rock from tunnel construction, optimize the construction step of the Guanshan tunnel at the all levels of surrounding rock and different section conditions of this tunnel, provided theoretical support for the rapid construction of this tunnel.Because of ANSYS finite element software have not the M-C yield criterion inte-rnal, using the D-P yield criterion (DPI) to approximate calculation that base on not isometric hexagonal circumcircle M-C yield criterion in geotechnical engineering numerical simulation, the result tend to unsafe. To solve this problem, firstly, this paper use the equivalent area D-P yield criteria(DP4) to correct ANSYS software that approach to the M-C yield criterion more accurately. And using APDL language to achieved the yield approach index (YAI) secondary development under the three-dimensional numerical simulation environment of ANSYS software, quantitative evaluation of the surrounding rock stability analysis for Guanshan tunnel has been achieved under these conditions of all levels of surrounding rock, different sections and different working cases,intuitive reflect the stress level of risk for tunnel surrounding rock under complex stress state and this result applied to the optimization of the tunneling construction steps.In this paper, the following works was been completed and draw the corresponding con-elusions:(1) The optimization for excavation construction method under the different sections at all levels of surrounding rock:It is advised that the Guanshan tunnel of grade Ⅱ、Ⅲsurrounding rock using full-face method of construction; grade Ⅳ surrounding rock using two-step method of construction, surrounding rock poor section can consider using the construction of the CD method instead; class Ⅴ surrounding rock single line section lot using two-step method of construction, two-lane section lot runnel using three-step method of construction, surrounding rock poor section can consider using the construction of the both side heading method instead.(2) Determine the length of each construction cycle’s step-size for established construction methods under the different sections at all levels of surrounding rock:It is advised that the Guanshan tunnel of grade Ⅱ each the footage length selecting3.6m proper; grade Ⅲ each the footage length selecting3.2m; grade Ⅳsurrounding rock single line section lot each the footage length selecting2m, two-lane section lot using1.5m; grade V surrounding rock single line section lot each the footage length selecting2m, two-lane section lot using1.2m.(3) Selecting the right construction step-size of the step method under the different sections at all levels of surrounding rock:It is advised that the Guanshan tunnel of grade IVsingle line section lot the length of bench no more than0.75D (about4m), two-lane section lot the length of bench no more than0.75D (about9m);class Ⅴ surrounding rock single line section lot the length of bench no more than0.5D (about3m),for two-lane section lot, the length of the middle bench no more than0.75D (about9m),the length of the lower bench no more than D (about12m).(4) Calculate the length of construction safety under the different sections at all levels of surrounding rock of tunnel early support conditions:It is advised that the Guanshan tunnel of grade Ⅱ the safety length of self-stability for this tunnel under the condition of primary support no more than125m; the safety length for grade Ⅲ no more than100m; grade IVsurrounding rock single line section lot the safety length no more than72m, two-lane section lot tunnel no more than18m; grade Ⅴ surrounding rock single line section lot the safety length no more than45m, two-lane section lot tunnel no more than7.5m.In this thesis, the concept of yield approach index (YAI) was been used, through the secondary development of ANSYS software and with its powerful to post-processing features to achieve the quantitative evaluation the stability of surrounding rock under the impact of tunnel construction, this way been used to guideline for engineering practice, these conclusions can provide some guidance on the Guanshan tunnel rapid and safe construction, it is hope that the methods and conclusions of this paper can provide information and reference for these similar projects in the future.