Study On Ground Settlement Induced By Shield Tunnel Construction In Nanjing Wei Three Pass River

Traffic congestion and environmental factors are creating a demand for greater utilization of underground spaces in urban areas.Excavation of tunnels in urban areas can induce considerable ground movements,which have negative effects on existing structures.Accordingly,the analyze of tunnel induced surface settlements is of high importance in tunneling construction especially in urban areas.Surface settlements of soil due to tunneling are caused by stress relief,subsidence due to movement of support by excavation and trend depending on several factors such as tunnel geometry,ground conditions,and so on.In engineering practice different design methods tend to be used available to estimate ground surface settlement varying from simple empirical and analytical formulations to advanced finite element analyses.Depending on the tunneling method,different procedures are applied for the modelling of the excavation and support sequence.Based on the above issues,this thesis “STUDY ON GROUND SETTLEMENT INDUCED BY SHIELD TUNNELLING METHOD” was carried out and aims to:Firstly,it begins with a summary of prediction of the tunnel induced surface settlement namely empirical solutions,analytical solutions and numerical solutions.by finite element method.Subsequently the characteristics of ground surface settlement due to tunneling and the causes for construction induced settlement are developed.The analysis of lateral and longitudinal settlement and the stability of excavation face have also been describedSecondly,this thesis introduces a construction background and scale of Nanjing Wei three passing river tunnel project in baojian village and natural conditions of Nanjing Wei three passing river tunnel construction are given.The data collected at the implementation phase of the Nanjing Wei three passing river Tunnel Construction Project have been thoroughly processed and analyzedThen,the numerical simulation analysis was performed by Finite Element Method(FEM)using numerical simulation software ABAQUS which focus is on three-and two-dimensional finite element analyses.Besides the influence of some basic modelling aspects of finite element analyses,the importance of adequately modelling the excavation and support sequence,in particular the appropriate boundary conditions are examined.The analysis of ground settlement under different tunnel buried depth and different grout quality condition was carry out.Finally,the numerical simulation result was compared with the field measurement data;moreover,the numerical simulation result and the field measurement data was compared with the empirical prediction methods such as Peck(1969),Atkinson and Potts(1977),O'Reilly and New(1982)and Mair(1993).The research shows that the obtained result from empirical prediction methods are good agreement between performed numerical analysis result and the field measurement data.In addition,the results indicate that ground surface settlement is sensitive to effect of some important factors such as tunnel geometry,ground properties tunnel buried depth and grouting quality.