| With the further expansion of our country’s infrastructure construction, the railways and roadscontinuously extend into remote and mountainous areas, where the tunneling engineering ofcomplex topography and geology is common. Tunnel with unsymmetrical loading is a commonproblem. But the present tunnel design specifications only provide unsymmetrical loading designformulas considering the topographic condition only. So the studies of the deformation damagecharacteristics of tunnel unsymmetrical loading, the cause of unsymmetrical loading and process ofconstruction are significant. With methods of theoretical analysis, numerical simulation and thescene monitoring, this thesis makes the following studies on the cause, construction and safety ofunsymmetrical loading tunnel relying on the related tunnel sections based on the Lishan tunnelingengineering of Hefei to Fuzhou railway.(1)In order to analyze the reasons for Tunnel with unsymmetrical loading, the unsymmetricalloading caused by common topography was chose to carry out plane finite element model. Themodel analyzed and compared the following two conditions: one is with fixed gradient slope andvariant cladding thicknesses, and the other is with fixed cladding thickness and variant gradientslopes. The conclusions are as follows: Under the condition of the cladding thickness being fixed,when the included angle between sloping surface and horizontal plane is below35°, theunsymmetrical loading caused by topography is of little difference and can be ignored; when theangle is above35°, surrounding rock stress of both sides and preliminary bracing are greatly affected,and the impact of unsymmetrical loading should be considered; when the angle is45°and thecladding thickness is above60m, its influence on Tunnel with unsymmetrical loading can be ignored.But it must be considered when the cladding thickness is below60m.(2)Combined with the basic theories of rock elastic-plastic and mechanical behaviors ofconstruction of tunnels, this thesis builds the model of the construction of tunnels in the Ansys withfinite element method.(3)Considering the geological conditions of unsymmetrical loading sections of mountaintunnels, this thesis carries out plane finite element model on full section method, bench method,CRD method, and double side drift method so to compare their influences on the displacements ofsurrounding rock, stress, primary support internal force and economic benefit, which prove that thebench method is much more proper. (4)Considering different excavation lengths, unsymmetrical loading section of mountain tunnelsis carried out with three dimensional simulation which indicates surrounding rock and supportingstructure’s mechanical effect on time and space. With comparions of different excavation lengths,2m is found to be proper.(5)This thesis sets up the mountain tunnel construction monitoring system and analzys the datawith exponential relation model to compare and verify the consistency of the data of regressionanalysis method and actual situations, which proves that the method chose for finite elementsimulation is rational.This thesis mainly uses the Ansys to make numerical simulation analysis on the construction ofunsymmetrical loading tunnels and make validation by field data at the same time which has acertain guiding significance on the design and construction of unsymmetrical loading tunnels. |
