CODING THE 'NEW IMPLICIT METHOD' IN MATLAB FOR PRELIMINARY TUNNEL DESIGN

Wallace Cavalcante Ferrão¹; Denise Bernaud Maghous¹

¹ Federal University of Rio Grande do Sul

doi:10.20906/CPS/CILAMCE2017-0026

Resumo

The tunnel design is a subject that demands a three-dimensional analysis dealing with two different players: the lining and the rockmass. Nevertheless, simplified methods like Convergence-Confinement Method are useful for preliminary studies. In most of the time, the traditional methods of getting the necessary parameters for design, convergences (closure) and stresses, do not consider a correct interaction between the two players. Concerning this, the New Implicit Method (NIM), that uses principles like those of the Convergence-Confinement Method, shows that the lining stiffness influences the convergence at the moment of lining installation of the tunnel. The NIM develops formulations for time-independent conditions (elasticity and plasticity) and for time-dependent conditions (viscoplasticity) of rockmasses where a non dimensional tunnel advance rate is an important parameter. A code in MatLab of NIM for rockmasses was developed and validated through Finite Element analysis in elasticity, plasticity for Tresca and Coulomb plasticity criteria and viscoplasticity with the same previous criteria. The FEM numerical analysis are performed with the numerical code GEOMEC91. This code uses the deactivation/reactivation method for the elements to simulate the steps of excavation and the lining installation. The obtained results gives an average accuracy of 12%. The code in Matlab is simple and its results agree very well with the numerical results, what represents a good approximation regarding geotechnical issues.

Palavras-chave: Tunnel Design; New Implicit Method; Convergence