| With the vigorous development of urban underground space,many large cross-section,large buried depth,long distance and complex shield tunnels have emerged.Up to now,26 super-large cross-section urban tunnels have been built and under construction in China,accounting for 62% of the world's total.The scale and speed of construction have led the world with remarkable achievements.However,under the background of the flourishing development of underground space,the phenomena of lining cracking and destruction,seepage and mud leakage of tunnel,longitudinal distortion and deformation of internal structure caused by longitudinal uneven deformation of tunnel are frequent.At present,there are few studies on the longitudinal structural characteristics and design model of super-large cross-section shield tunnel.Based on Shandong Province's key research and development project "Longitudinal Deformation Characteristics and Design Model of Shield Tunnel in Variable Composite Strata Based on Soil-Water Coupling",this paper takes the Yellow River tunnel project in Jinan as the project background,a size effect and tunnel longitudinal stiffness between efficiency and tunnel under complex strata stiffness and longitudinal deformation relationship and the size effect and the longitudinal performance of shield tunnels in composite strata are analyzed and studied by means of theoretical analysis.Through model test and numerical simulation,the factors causing longitudinal uneven deformation of super-large cross-section shield tunnel are analyzed.Based on Winkler elastic foundation beam theory and modified longitudinal equivalent continuity model of shield tunnel,the longitudinal design model of shield tunnel based on super-large section and composite stratum is constructed.The longitudinal design method of super-large section shield tunnel is proposed.The main work and results of research of this paper are as follows:(1)The longitudinal performance of lining structure of shield tunnel is deeply studied from the effect of dimension and the complexity of crossing strata.Based on the longitudinal stiffness model of shield tunnel with the influence range of transverse stiffness and annular joint,the relationship between the dimension effect and the longitudinal stiffness efficiency of the tunnel is established,and the longitudinal stiffness efficiency and the longitudinal equivalent stiffness of the tunnel crossing the Yellow River are obtained.By analyzing the influence of cohesive soil and sandy soil on tunnel deformation,the longitudinal deformation mechanism of tunnels in two different strata is found.And the relationship between tunnel stiffness and longitudinal deformation based on composite strata is established.(2)The influencing factors of longitudinal deformation of shield tunnels are analyzed from construction and operation stages,and the main factors causing the longitudinal deformation of the super large section shield tunnel are found.(3)Based on similarity theory,reasonable selection of physical quantities is made to determine appropriate similarity ratio and tunnel and bolt model materials to meet similarity requirements.According to the geology of the Yellow River area in Jinan,the model silty clay and model sand pebble soil satisfying the requirements are prepared through geotechnical tests.Through model tests,the longitudinal deformation law and mechanical characteristics of shield tunnels in silty clay and sandy gravel composite stratum under static loading are studied,and the influence of soil characteristics on the longitudinal deformation of tunnels is searched.(4)A three-dimensional finite element model for the coupling of stress field and seepage field under shield tunnel excavation is established by using finite element analysis method.The influence of different soil layers,different water pressures and different burial depth on the longitudinal deformation and mechanical characteristics of the shield tunnel with super-large cross-section through the Yellow River is discussed.(5)According to Winkler elastic foundation beam theory and modified equivalent longitudinal continuity model of shield tunnel,the longitudinal design model of shield tunnel based on super-large section and composite stratum is constructed,and the longitudinal design method of super-large section shield tunnel is put forward. |
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