| Since the 21 st century,with the acceleration of urbanization and the diversification of transportation modes,the demand for road construction has gradually increased.Underground space for people is a treasure,full of infinite charm,therefore,human gradually develop and use underground space.Shield tunnel is a structural form with high utilization rate of underground space,which plays an important role in the construction of urban underground rail transit.Shield segment is the skeleton of the whole subway tunnel,and the safety of segment structure has a crucial impact on the whole subway project,so it is very important to consider the safety and economy and meet the reasonable requirements of segment design.The innovation of this thesis is mainly reflected in the fact that most other scholars only study the internal force of the segment,and this thesis not only studies the internal force,but also analyzes the stress to explore the mechanical characteristics of the shield segment,the main contents are as follows:(1)This thesis expounded the shield method and segment lining,the finite element analysis model of the interaction between the tunnel segment lining structure and the surrounding soil was established by using the finite element theory and the commonly used shield segment calculation model and load calculation method.(2)The factors influencing the mechanical characteristics of shield segment were analyzed.The static analysis of shield tunnel segment structure under the influence of lateral earth pressure coefficient,concrete strength grade and segment diameter were mainly studied.The results show:with the increase of lateral pressure coefficient,the maximum bending moment,axial force,shear force,von Mises stress,the first principal stress and the maximum displacement of segment structure decrease,showing an obvious downward trend.When the lateral pressure coefficient increases by 0.1,the maximum bending moment of shield segment decreases by about 144 k N·m,the maximum axial force decreases by about 50 k N,and the maximum shear force decreases by about 62 k N;the maximum von Mises stress decreases by about 3.1MPa,the maximum first principal stress decreases by about 3.8MPa,and the maximum segment displacement decreases by about 0.325 cm.(3)With the increase of concrete strength grade,the maximum bending moment,maximum shear force and von Mises stress of the segment increase slowly,the maximum displacement decreases,and the maximum axial force has almost no change.With the increase of the segment diameter,the maximum bending moment,shear force and the first principal stress of the segment gradually decrease,while the maximum axial force and the maximum displacement gradually increase;the change of the segment diameter has little effect on the von Mises stress and the first principal stress,and the stress decreases slowly with the increase of the segment diameter.(4)The basic method of modal analysis was expounded,and the first six modes of segment structure were calculated by block method.Time history analysis method was used to analyze the seismic dynamic response of segment structure of shield tunnel.The results show that the maximum stress and displacement of the segment under vertical earthquake are greater than that under transverse earthquake,and the maximum stress of the segment under vertical earthquake wave is about 23.5% higher than that under transverse wave,and the maximum displacement is about 18.6% higher than that under transverse wave.The maximum stress of the segment waist and the maximum displacement of the vault are greatly affected by the earthquake load,that is,the segment waist and the vault are the most unfavorable positions. |
