| In recent years,there has been an increasing number of underwater tunnel projects in China.Due to the complex stress environment of shield tunnels during construction,and the influence of seepage field on tunnels through rivers,studying their construction mechanical effects and mechanical characteristics under fluid solid coupling has practical research significance;In terms of the design of cutterhead cutters,it is of great research value to study the impact of various cutting tool working parameters on shield tunneling in combination with practical engineering.Taking the tunnel crossing the Yangtze River section under Chongqing Metro Line27 as the background,the mechanical effects of shield tunnel construction are studied by combining theoretical analysis and numerical simulation to design different water level conditions with the minimum and maximum soil cover thickness sections.Establish a three-dimensional fluid solid coupling numerical simulation model for the most dangerous working conditions,and conduct research on the distribution law of seepage field and mechanical characteristics such as stress deformation of lining segments during the construction process.Based on geological exploration data,rock and sandstone with higher strength were selected as the rock breaking soil.Combined with theoretical stress models and rock breaking simulation,the impact of tool working parameters on the rock breaking effect of the tool was analyzed and appropriate suggestions were given.The main work and research results are as follows:(1)Research on the mechanical effects of shield tunnel construction under different water level heights.Six working conditions were designed for different water level heights(historical highest water level,multi-year average water level,and on-site measured water level)under the minimum and maximum soil cover thickness sections.Numerical simulation was used to study and analyze the construction mechanical characteristics under different working conditions.By comparison,it can be concluded that as the water level rises,the deformation of the tunnel surrounding rock and pipe segments continues to increase,the stress becomes more complex,and the pipe segments are more likely to be damaged.It is concluded that condition two is the most dangerous condition for the tunnel.(2)Research on the three-dimensional fluid structure coupling model for the most dangerous working conditions.Combined with the fluid solid coupling theory,the finite difference software FLAC3 D is used to establish the three-dimensional numerical model of fluid solid coupling during the construction period of the most dangerous working condition II,and study the characteristics of the surrounding rock stress,displacement,seepage field,ground settlement law and the deformation characteristics of lining segments under the fluid solid coupling.(3)Research on the rock breaking principle and force model of shield machine cutting tools.Study the principles of cutter head and tool arrangement for slurry shield tunneling machines,study the selection of cutter head and tool classification for slurry shield tunneling machines,summarize the functions and working principles of various tools,analyze the cutting mechanism of cutters and rollers,and summarize the force models of cutters and rollers.(4)Establish a rock breaking model for shield tunneling machine cutting tools for simulation research.Select a reasonable constitutive model as the constitutive model for geotechnical simulation research,and simulate the rock breaking process based on the Abaqus finite element analysis platform.Establish finite element models for cutting rock and soil with cutting cutters and rolling cutters,and analyze the impact of different structural working parameters of cutting cutters and rolling cutters on the cutting rock performance of cutting tools based on theoretical force models and finite element results.It is concluded that the best rock breaking effect is achieved when the current angle of the cutting tool is 15°,the width of the tool is 200 mm,the cutting depth is 15 mm,the cutting speed is 1000mm/s,and the tool spacing is 160mm;When the penetration of the rolling cutter is 9mm,the linear speed is 1000mm/s,and the spacing between the cutters is 90 mm,the rock breaking effect is the best. |
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