ABSTRACT
The present research aims to investigate the optimal design parameters of the tunnel face pre – support, where the conventional tunnel excavation method is implemented, by using forepoling umbrella and/or fiberglass nails. The research is based on numerical investigation, in both cases of shallow and deep tunnels, by usage of the Simulia ABAQUS FEM. During the numerical analysis, the tunnel face deformation (extrusion) and the tunnel face pre – support measures response were recorded, in occasions of different rockmasses and various tunnel overburden heights. From the results of the several design parameter, was specified the optimal length of the support measures in order to achieve the maximum effectiveness. For both tunnel face reinforcement with fiberglass nails and/or tunnel face pre – support by forepoling umbrella, were exported non – dimensional nomographs and expressions, in order to be useful for the tunnel designer.
