| Nowadays,Hefei Rail Transit Line 2 is in full swing,the construction of rail transit projects is in urban bustling places and tunnel projects are mostly located in the trunk roads and below the street buildings.Accordingly,construction risks are getting higher and higher.In this thesis,with the help of Qian Shan Road Station.Subway Tunnel of Hefei City Rail Transit Line 2.Application of Finite Element Software MIDAS / GTS NX realizes Two-Dimensional and Three-Dimensional Numerical Simulation about Temporary Support Demolition in CRD Construction of Shallow Buried Excavation Tunnel.The displacement deformation of surrounding rock and the stress change of lining caused by temporary support structure of tunnel are analyzed emphatically.In addition,The different length of the dismounting support is simulated,and further,the influence of the sequence dismantling temporary shoring and the interval dismantling temporary shoring on the tunnel surrounding rock is analyzed.The main work and conclusions are as follows:(1)The thesis summarizes the study on temporary support structure removal about Home and abroad and the related deformation rules of the tunnel surrounding rock support structure.At the same time,the thesis presents the research content and research methods of this paper.(2)The deformation analysis of the tunnel's straight wall curved arch,side wall and bottom plate shows that The impact of the lateral temporary support structure on the tunnel surrounding rock is very weak,but the convergence displacement changes slightly.The main deformation Takes place in the process of vertical temporary support structure demolition.In the process of removal,the maximum absolute value of the stress increases gradually with the Demolition process when the top support structure is dismantled firstly.The maximum absolute value of the stress increases first and then gradually decreases with the removal process when the bottom support structure is dismantled firstly.About Support structure demolition,Whether it is to consider the impact of the lining stress or the deformation of the tunnel surrounding rock.Remove the top support structure first is superior to remove the bottom first.(3)In the process of temporary support removal,when the dismantling temporary shoring length is less than 9 meter,the displacement of the surroundingrock will increase with the increasing of the length of a support Demolition,but the increase is small and the change is not obvious.However,when the dismantling temporary shoring length is longer than 9 meter,the displacement of the surrounding rock will increases with the increasing of the length of the support Demolition.This may result in the local instability of the surrounding rock due to the dismantling temporary shoring length is too large.Therefore,in order to control the displacement of the surrounding rock caused by the excessive dismantling temporary shoring length and combining with the results of this simulation determine that the maximum length of 6 meter is more reasonable of the temporary support structure on Hefei rail transit line 2 Qian Shan Road Station shallow buried tunnel construction.(4)The settlement value of the tunnel surrounding rock increases smoothly and regularly when the temporary support structure is removed intervally,and the settlement of the tunnel surrounding rock increases suddenly in a certain condition.And the settlement increase is larger than that of the interval temporary support structure.Therefore,the impact of the Temporary support removed from the interval for the settlement of the surrounding rock is less than the temporary support removed in order.(5)The comparison between numerical simulation and actual results shows that the displacement law,the displacement size and the maximum displacement law of the deformation are basically similar,the change trend is roughly the same,and the difference is small,so the rationality of numerical model is verified. |
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