Centrifugal modeling of continuous shallow tunnels at active normal faults intersection

Abstract

Both traffic and water conveyance tunnels’ networks are being extended in many earthquake-prone areas as to its faulting sense. Active fault and tunnel intersections lead to an intense coercive displacement of tunnel lining. Here, a series of 1/60 scale centrifuge tests are run on such intersections normal dip-slip fault mechanism. Experimental surface faulting model of 60 degrees is applied on a set of soil and tunnel models through a fault simulator box. The Location and the mechanism of failure together and damage states of the modeled tunnels are assessed, and the fragility curves related to each damage state are plotted. Tunnels are very vulnerable to normal faulting; therefore, a displacement of about 20 to 30 cm could generate the initial cracks in the lining. Any increase in displacement would lead to cracks expansion and enlarging the displacement to 50 cm, causing soil and rockfall into the tunnel, thus blockage. Fault rupture propagation is assessed in soil deposits with and without tunnel. The effects of fault displacement and tunnel collapse on the ground surface, including fault scarp, graben and sinkhole, are observed and assessed. The existence of each one of these surface features can be a potential risk for both surface and buried structures.