Study On Internal Force Effect Of The Closely Spaced Tunnels Excavation On The Surface Frame Structure Buildings

With the rapid development of the city, the urban traffic is becoming crowded.People make full use of the ground space and develop to the underground at the sametime, so the tunnel becomes an important part of the underground development, whilethe urban tunnel excavation will affect inevitably the surface buildings.On base of Chongqing Nanshan Tunnel, in order to analyze various factorsaffecting the calculation result comprehensively and rationally, and decrease the timesof simulation calculation, this paper will be adopted orthogonal experiment designmethod to design numerical simulation plan and ANSYS finite element analysissoftware for three-dimensional elastic-plastic analysis.Firstly, studying the stress and strain condition of the surface frame structurewithout tunnels is prepared for the following comparative analysis. Then studying thedisplacement and the stress field of the closely spaced tunnels surrounding rock andthe stress field of the frame structure independent foundation in the condition of threefactors combination of the closely spaced tunnels center line-building axis distance(L), the soil thickness(H) of the tunnel top and surrounding rock rank, that canconclude the change rule of surrounding rock, stress and the frame structureindependent foundation and the placement of max displacement and max stress in thedifferent of construction condition. According to the displacement and stress of thesurface frame structure, studying the internal stress distribution of the surface framestructure above the closely spaced tunnels can find out the key part (the mostdangerous section) of the frame structure. The result shows that the key part of theframe structure is in the middle of the beam-column joint by simulation analysis ofthe nine construction condition.In order to better acknowledge the effect of the closely spaced tunnels excavationon the surface frame structure, this paper will research the protective measures of theframe structure building during construction to minimize the broken degree of thetunnel excavation on the surface frame structure and further to analyze the stresscondition and various factors sensitivity degree of the key part of the beam-columnjoint. The research shows that the better test plan (the biggest impact test plan) is: thetunnel center line-building axis distance L=0m, the soil thickness of the tunnel topH=36m and the â…£rank of the surrounding rock. By sensitivity analysis, to analyzethe effect of the various factors on the frame structure is through inspecting the threetest indicators of the frame structure bending moment, axis stress and shear stress. The poor analysis indicates the effect degree of three factors on the frame structurefrom high to low is: the tunnel center line-building axis distance (L), the rank of thesurrounding rock and the soil thickness (H) of the tunnel top.