This paper describes a numerical simulation with 3D finite elements of a tunnel. The viscoplastic law of Perzyna represents the rockmass behavior. The concrete, shotcrete or precast, is modeled as a viscoelastic material through the Maxwell and Kelvin chain models. Finite element simulations are performed by incorporating subroutines for viscoelastic concrete models in the ANSYS code. The method to simulate tunnel excavations is by activating and deactivating elements in sequential steps. In the first part of the paper two validations are performed. The analytical solution and the deformation achieved on the stabilization in the ANSYS code are compared with an unlined tunnel. A lined tunnel, with an elastic and viscoplastic rockmass combined with an elastic lining, is compared with the results of the GEOMEC91 code. In the second part, it is compared the same tunnel with two different concrete lining for two chain models. Finally, it is modeled the Kielder experimental tunnel, which in situ measured data is available.
The tunnel design is a subject that demands a three-dimensional analysis dealing with two different players: lining and rockmass. The traditional methods of getting the necessary parameters for design do not consider a correct interaction between the two players, but the New Implicit Method (NIM) takes this characteristic in its core and develops some formulations for elastic, plastic and viscous rockmasses. Understanding that the stiffness of the lining and the distance between the lining and the tunnel face change the convergence of the tunnel, a code in MatLab for NIM is validated through Finite Element (FEM) with its results being presented. The validation of this method was compared with FEM analysis and the results obtained an average accuracy of 12% what represents a good approximation regarding geotechnical issues.
ResumoThe tunnel design is a subject that demands a three-dimensional analysis dealing with two different players: lining and rockmass. The traditional methods of getting the necessary parameters for design do not consider a correct interaction between the two players, but the New Implicit Method (NIM) takes this characteristic in its core and develops some formulations for elastic, plastic and viscous rockmasses. Understanding that the stiffness of the lining and the distance between the lining and the tunnel face change the convergence of the tunnel, a code in MatLab for NIM is validated through Finite Element (FEM) with its results being presented. The validation of this method was compared with FEM analysis and the results obtained an average accuracy of 12% what represents a good approximation regarding geotechnical issues.Keywords: tunnel design, new implicit method, elastic, plastic and viscoplastic rockmass, convergence.O dimensionamento de túneis requer uma análise tridimensional lidando com duas estruturas muito diferentes: o maciço e o revestimento. Os mé-todos simplificados tradicionais de dimensionamento de túneis não consideram a correta interação entre essas duas estruturas. O "Novo Método Implícito" leva em consideração a correta interação e é desenvolvido para maciços elásticos, plásticos e viscoplásticos. O parâmetro chave desta interação é a convergência no instante da colocação do revestimento que é afetada, entre outros, pela rigidez do revestimento. Um código em MatLab do NIM foi desenvolvido e validado com resultados de cálculos numéricos em elementos finitos. Os resultados desta comparação fornecem uma precisão de 12%, demonstrando um ótimo resultado para obras geotécnicas.Palavras-chave: dimensionamento de túneis, Novo Método Implícito, maciços elásticos, plásticos e viscoplásticos, convergência.
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