Study On Three Dimensional Numerical Modeling Method Of Shield Tunnel And Mechanical Properties Of Lining

As the development of economics of our country and demand of acceleration of urbanization process according to China's 13th plan of five-year national development,Urban public transport infrastructure in large scale is inevitable.When it comes to construction of subway tunnels,shield method is preferred due to its lesser influence upon ground transportation and producing activity.The key to design shield tunnel lining is to adopt the structural model which can reflect actual working condition.Currently,there are five mainstream tunnel lining horizontal numerical analysis methods/models:wont method,revised wont method,multi-hinge loop model,beam-spring model and beam-joint model.The vertical analysis methods/models are:the vertical beam-spring model and the vertical equivalent continuous model.These methods/models all simplify the segment to beam in horizontal direction and length wise direction and consider structural properties in both direction respectively without exception.In many cases it is difficult to reflect actual wording condition of shield tunnel segment using methods/models above.In view of existing study on statics of shield tunnel lining models,this paper uses finite element software ANSYS and its programming language APDL to modeling joint and segments and study effect of underneath pass construction on inner force and deformation of existing shield tunnel.The main research contents are below:(1)Two-dimensional water proof gasket numerical model is built to achieve its mechanical properties.Three-dimensional joint numerical model in considering of mechanical properties of water proof gasket is built to calculate its flexural rigidity which shall be used in shell-spring model of shield tunnel lining.(2)Three dimensional shell-spring shield tunnel lining model is set.Shell elements are used to simulate lining segments and spring elements are used to simulate joints.Flexural rigidity of each joint bearing different axial force shall be calculated by iterated calculation.Distribution rule of bending moment and axial force along the lining is study in both straight joint and staggered joint assembling condition.(3)Three dimensional solid-spring shield tunnel lining model is set.Solid elements are used to simulate lining segments,Spring elements are used to simulate bolts and contact elements are used to simulate contact action between segments.Nonlinearity of bending/axial/shear properties of joints can be achieve by the assembly of elements mentioned above.Distribution rule of bending moment and axial force along the lining is study in both straight joint and staggered joint assembling condition.Results of shell-spring,solid-spring,wont method and multi-hinge loop model are compared.(4)Numerical model is build to simulate the whole construction process of shield underneath passing existing shield tunnel.Thermal-volumetric strain analogue method is adopted to simulate volume reduction of grouting slurry during condensation.Existing tunnel is simulated by solid-spring model to study its inner force and deformation under the influence of underneath pass construction.Variation regularity of the inner force of bolts,the opening and staggered distance of joints are also deduced.