Integrating Terrestrial Laser Scanning and Discrete Fracture Networks Approaches for Tunnel Modelling in Fractured Rock Masses
Pedro Pazzoto Cacciari1; Marcos Massao Futai1
1 EPUSP
Resumo
Several old tunnels in Brazilian roads and railways were constructed in rock masses without any support system. Recently, some of these tunnels are presenting localized problems of rock falls related mainly with rock discontinuities distributions and some punctual weathering processes. The Vitoria-Minas Railway (VMR), owned by VALE SA, is one of the oldest railways in Brazil and has about twenty tunnels in this condition, requiring geological and geotechnical investigations to provide parameters and evaluations of the stability state. Considering this problem, a partnership between Polytechnical School of University of São Paulo and VALE SA was initiated to propose a methodology and study these tunnels. The lengths of these tunnels varies from hundreds of meters to a few kilometers, which makes conventional field discontinuity mapping a strenuous and time-consuming job when considerable detail is required. In addition, with the conventional geological mapping in tunnels, it is difficult to obtain the actual position and geometrical parameters (generally described as orientation, frequency and size) of all discontinuities, mainly in the higher regions of the tunnel section. This paper presents an approach to tunnel modelling in fracture rock masses using discontinuity mapping obtained from terrestrial laser scanning images and discrete fracture networks generations. A faro focus 3D laser scanner (Faro Inc.) was used to generate the tunnel point clouds (3D tunnel images) and the rock discontinuities were mapped in these images using the Polyworks (InnovMetric Software). The discontinuity analyses were performed in Visual Basic-Excel programs and both the discrete fracture networks and 3D block model were generated in 3DEC software (Itasca Consulting Group). The great amount of discontinuity data obtained by terrestrial laser scanner mapping allows the application of several sophisticated discontinuity analyses (orientation, length and frequency), and the definition of the volumetric intensity of each disconti
Palavras-chave: Tunnel; Terrestrial Laser Scanner; Discrete Fracture Networks