Behaviour of deep immersed tunnel under combined normal fault rupture deformation and subsequent se.pdfVIP

Bull Earthquake Eng (2008) 6:213–239 DOI 10.1007/s10518-007-9055-0 ORIGINAL RESEARCH PAPER Behaviour of deep immersed tunnel under combined normal fault rupture deformation and subsequent seismic shaking Ioannis Anastasopoulos · Nikos Gerolymos · Vasileios Drosos · Takis Georgarakos · Rallis Kourkoulis · George Gazetas Received: 22 June 2007 / Accepted: 25 November 2007 / Published online: 18 December 2007 © Springer Science+Business Media B.V. 2007 Abstract Immersed tunnels are particularly sensitive to tensile and compressive defor- mations such as those imposed by a normal seismogenic fault rupturing underneath, and those generated by the dynamic response due to seismic waves. The paper investigates the response of a future 70 m deep immersed tunnel to the consecutive action of a major nor- mal fault rupturing in an earthquake occurring in the basement rock underneath the tunnel, and a subsequent strong excitation from a different large-magnitude seismic event that may occur years later. Non-linear finite elements model the quasi-static fault rupture propagation through the thick soil deposit overlying the bedrock and the ensuing interaction of the rup- ture with the immersed tunnel. It is shown that despite imposed bedrock offset of 2 m, net tension or excessive compression between tunnel segments could be avoided with a suitable design of the joint gaskets. Then, the already deformed (“injured”) structure is subjected to strong asynchronous seismic shaking. The thick-walled tunnel is modelled as a 3-D massive flexural beam connected to the soil through properly-calibrated nonlinear interaction springs and dashpots, the supports of which are subjected to the free-field acceleration time histo- ries. The latter, obtained with 1-D wave propagation analysis, are then modified to account for wave passage effects. The joints between tunnel segments are modeled with special non-linear hyper-elastic elements, p