Numerical Modelling of Tunnel Based On a Non-Contact Geological Survey Method

The development of new methods for the geostructural survey that do not need direct contact with the rock mass have been developed by several authors and applied to rock slopes. The new idea of this work was to apply a non-contact method based on photogrammetric techniques at the tunnel excavation for a complete rock mass 3D geometrical reconstruction. The core of the method is the possibility to obtain all the information by taking just few photographs, reconstructing automatically a digital surface model (DSM) of the excavation surface and then applying a code (Rockscan) for the determination of the discontinuity orientation and location on the excavation surface. The rock mass knowledge allowed to perform both equivalent continuum and discrete modelling and to compare the results with in situ convergences. The method has been developed through the application to two real cases: a mining gallery in dolomite underground quarry in Tassullo (TR) and a railway tunnel face in the Parma province (North Italy). The paper describes the method, the developed code and their application to the tunnels, showing the influence of the rock mass structure to the anisotropic convergence.