Study On Unsymmetrical Load Stress Ratio And Structural Optimization Of Shidaoyangcha Tunnel

Tunnel construction in China is in rapid development stage.Due to surrounding rock stress of the left and right sides of the unsymmetrical load tunnel is not uniform,it caused that the initial support and secondary lining is under the unsymmetrical load.The current study of the unsymmetrical load tunnel mainly concentrated on the support of unsymmetrical load tunnel and surrounding rock stress,construction,monitoring,but the study on quantitative definition of unsymmetrical stress in unsymmetrical load tunnel is not much;On the other hand,due to the complexity of the unsymmetrical load tunnel,the asymmetric distribution of the load,and the imbalance of support structure stress,etc.,difficulties was arised in the construction and support.In this paper,the unsymmetrical stress ratio of shallow-buried tunnel is quantitatively defined by means of finite element numerical simulation.Relying on the shallow-buried the unsymmetrical section of Shidaoyangcha tunnel,the asymmetric initial support parameter optimization design was carried out for the unsymmetrical load tunnel.The support strengthening was carried out for the weak part,and the support weakening was carried out for the safe part.The main achievements are as follows:(1)Based on the engineering support of shallow-buried side section of Shidaoyangcha tunnel and using numerical simulation method,we can draw that overburden depth,surface inclination and rock class all influence unsymmetrical stress ratio of lining and surrounding rock unsymmetrical stress ratio.In both lining and surrounding rock,spandrel stress ratio has obvious change rule with the change of overburden depth,surface inclination angle,and the level of surrounding rock.The abutment can be used as an effective location to judge whether the tunnel is unsymmetrical or not.(2)Combined with the Code for railway tunnel design,with analysis of lining stress ratio and surrounding rock stress ratio respectively,we can draw a conclusion that using the stress radio of surrounding rock arch shoulders to determine whether it is a unsymmetrical load tunnel when rock class level for ?stone??soil ??.(3)Based on the geological conditions of shallow buried bias section of Shidaoyangcha tunnel and considering the bias load on the tunnel,the asymmetric structural optimization of the selected section is carried out on the concrete thickness,bolt length and bolt spacing.By means of the indexes of the plastic zone surrounding rock analysis comparison including stress ratio,the lining of the axial stress of surrounding rock,bending moment and the anchorage force of bolt,it is determined when the concrete spray layer thickness of 25 cm,anchor length of buried side in 3.5 m,shallow buried side taken 3 m,bolt spacing buried side in 0.8 m,shallow buried side take 1.0 m that is the section optimal design conditions.