Study On Floating And Control Of Tunnel Segments Using Method Combined With Minie Tunneling Method And Shield Method

In recent years,with the development of underground rail transit,the application of method combined with minie tunneling method and shield method has solved the difficult problem of shield tunneling in some hard rock areas.Because of the particularity of the construction method,the phenomenon of segment floating in the shield construction has become more obvious,which has attracted the attention of some construction and researchers.This paper mainly studies the causes and control methods of floating phenomenon of combination construction method:According to the Wuhan Metro Line 3 project,this paper systematically analyzes the technological process and construction features of the combination construction method section,and gets some factors that may cause the segment to rise.For the local float of segment,this paper presents a clear calculation procedure and method based on the basic principle of mechanics.Considering the contact surface,axial pressure,grouting pressure,grouting capacity,shear strength and deformation of the adjacent segment,the maximum float and maximum grouting pressure of the segments under different working conditions are calculated.For the whole float of segment,numerical analysis is used.Based on previous research on shield method,a vertical equivalent continuous model suitable for combination method is put forward in this paper,and the model is adjusted and improved according to the construction practice of the support project.In this paper,the bolt at the segment joint is equivalent to the bolt ring,and the stiffness of the equivalent bolt is reduced according to the deformation relation between the bolt and the segment so as to satisfy the simulation of the model to the actual situation.Through the analysis of an engineering example,it is shown that the maximum float amount calculated is approximately consistent with the monitoring data.Based on the longitudinal equivalent continuous model,the main factors affecting the floating of the segment are quantitatively calculated,includes: The number of bolts,the time of grout solidification,the speed of the shield machine,the amount of grouting and the location of grouting.Through the fitting of the curve relation of the calculation results,the relation between the different factors and the maximum float of the segment is obtained.Different parameters of the equation are adjusted so as to effectively control the floating amount of the segment,which provides a theoretical basis for the similar project to control the rise of the segment.Finally,the problems and further research are discussed briefly.