Analysis Of Soil Deformation And Pile Response Due To Tunneling In Soft Soil Considering The Creep Behavior

With the process of modernization,the construction of urban metro line also reaches into rapid development stage.However,related problems also become severe during the construction periods.Especially in regions with clay widely spread,it is inevitable that some metro lines have to cross the clay,which needs to take account of the problem that the long term displacement of clay is large.Large soil displacement or apparent differential settlement will lead to disadvantageous effect on the structure of tunnel and adjacent buildings.To study the problems appeared when tunnel crosses clay,this thesis firstly studied short-term and long-term deformation of soil by numerical and analytical methods,and then established numerical model to evaluate the influence of soil deformation on adjacent piles.The main contents of this thesis include three parts:(1)The features of relation between stress and strain of basic creep components and their series or parallel connections are introduced.And the regulation of the relationship between stress and strain of CVISC model is analyzed.The CVISC model,which is mainly used in this thesis,can appropriately simulate the three stage of creep displacement development:initial stage,decelerate stage and accelerate failure.(2)A new analytical solution of long term soil displacement under plane strain condition is derived,and then an improved solution to consider three dimension effect is furtherly proposed,which aims to consider the effect of tunnel advance.The effect of soil buck modulus,advance rate,cohesion,and friction angle on the long term soil development is studied.The results show that,soil buck modulus,cohesion and friction angle all have important influence on both the rate of displacement and the final displacement,tunnel advance rate only has apparent effect on the rate of displacement during construction period,but has trivial effect on the final displacement of soil.(3)The excavation and operation period are simulated in two stages.In the first stage,the displacement controlled method is applied in the construction process,the result is verified with related researches.In the second stage,the creep behavior is considered after tunnel construction,the effects of the four mechanical parameters in the creep model on soil deformation and pile response are discussed,and the relationship between creep parameters and long term settlement is summarized to predict long term settlement in practice.The results shows that the internal axial force and moment of pile increase apparently when the creeping behavior of soil is considered.