Research On Construction Stability Of Shenyang Metro Line 9 Ji-Wang Section And Analysis On Monitoring Of Support Structure

With the increasing speed of new subway lines in our country, the connection of two parallel metro tunnel crossing more and more. Opening a horizontal channel in Central Line made soil stress conversion more frequently, so the ingate become the weak parts of the structure. How to choose the best excavation sequence is the necessary condition to gurantee the stability of tunnel structure when it has multiple ingate, so research on construction stability of Shenyang metro line 9 Ji-Wang section with multiple ingate and analysis on monitoring of support structure has very important significance.For the engineering background of Shenyang metro line 9 Jiwang tunnel with multiple ingate in this study,this paper used numerical simulation and field detection. The parallel double line tunnel has two section sizes, the span of standard section is 6.4m, the span of the big cross section which contains crossing line is 13.3m. Using FLAC3D and the positive hole of 4 tunnel cross channel numerical simulation research, and by simulating the construction process,on the surface settlement, internal force, supporting structure internal force distribution to the result of the calculation analyze, studying the stability of the tunnel construction process.By means of three dimensional numerical model for optimal excavation scheme, it is concluded that the most unfavorable position in the process of tunnel construction, and the primary support in these parts of the steel grid layout on the reinforcement stress meter and optical fiber grating sensors, the test section supporting structure internal force and deformation monitoring. Through the analysis of field monitoring in the standard cross section in the process of excavation, the changing rule of the axial force of steel grating as follows:In excavation of double hole diameter, the fastest growing lining structure reinforcement stress in the early, after growth rate dropped significantly, scope for five times the hole diameter, and in the process of tunnel excavation, the lining structure stress at the beginning of the process is a gradual process, not imposed by the surrounding rock bolting supporting structure immediately after assume all forces.Using the standard cross section adjacent large cross section the influence of excavation on the internal forces of the standard section the first primiary lining at the same time. On the internal forces of the big cross section the first primiary lining monitoring at the same time, using fiber Bragg grating sensor for large cross section of the three sections of steel grille deformation monitoring and analysis line is given priority to with compression, converted to maximum compressive stress is 4.14 MPa, it’s smaller than design value of concrete compressive strength of the first primiary lining, the initial lining structure can meet the capacity very well.