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CASE STUDY: THE INFLUENCE OF TUNNELLING ON SLOPE STABILITY

Session: Landslides and Slope Stability I / Mouvements de terrain et stabilité des pentes I

Nicholas Vlachopoulos, Royal Military College of Canada (Canada)
Ioannis Vazaios, Queen's University (Canada)

Tunneling projects oftentimes involve the design and construction of two adjacent (twin) tunnels with respect to underground infrastructure projects for road, railway or subway systems within mountainous terrain. Currently, there is limited investigation associated with the interaction generated between the excavations of two adjacent tunnels, especially in conjunction with slope stability issues. One of the major drawbacks with regards to such inherently complex, 3D investigations (i.e. a precursor to design) is the increased computational cost required to model the detailed three-dimensional excavation process utilizing 3D numerical analysis tools. As such, the use of idealized two-dimensional simulation can be employed in order to draw selected preliminary results with respect to the impact of the interaction between twin tunnels constructed within or adjacent to slopes. Despite of being conservative, these slope stability problems can be satisfactorily simulated in two dimensions. In this particular paper, twin tunneling excavation interaction within slopes is investigated utilizing 2D numerical models for tunnels close to the ground surface within weak rockmasses. A case study of the S3 tunnel of Egnatia Odos is also incorporated in order to highlight the very real requirement to take such factors into consideration prior and during the twin tunnel design stage.