Effect of voids on the seismic vulnerability of mountain tunnels

Developments in Seismic Vulnerability Assessment of Tunnels and Underground Structures

“…Zi et al [56] examined the effect of voids that may be found behind the linings of mountain tunnels in rock on the seismic vulnerability of the tunnels. A deeply buried two-lane expressway tunnel in western China was selected as case study.…”

“…Some studies used 2D numerical models of the examined ground structure configurations to perform pushover analyses, to estimate the structural capacity of, and set the thresholds for, the damage states to develop fragility functions. In most cases the general-purposed FE code ABAQUS was employed to perform the analyses (i.e., more than half of the studies) [56,[63][64][65][66]82,84,85,[89][90][91][92][93][94]. Other FE codes, such as PLAXIS 2D [61], MIDAS [51,60], and SAP2000 [79,80] were also used.…”

“…In the simplest case, a linear elastic model [53,54], or approaches that employ the equivalent linear approximation in simulating the effect of the nonlinear response of ground under seismic shaking, were employed [63][64][65][66][67][68][69][70][76][77][78][79]. Nonlinear models that employ a Mohr-Coulomb yield criterion were also used widely [44,52,55,56,60,72,73,82]. In some studies, these models were calibrated by adjusting the stiffness and damping of the examined ground, based on results of separate 1D soil response analyses, aiming for a more realistic simulation of the ground response under lower earthquake-induced strains [52,65,71,73].…”

“…Regarding lining behavior, most studies referring to mountain tunnels in rock or bored tunnels in alluvial employed a linear elastic model [51][52][53][54][55][56]60,61,65,[70][71][72][73]79]. The damage index and the damage state thresholds were defined using a separate section analysis for the examined liners, accounting for the effect of axial loading on the capacity of the liners in a simplified manner.…”

“…Andreotti and Lai [44] reported a better correlation of the computed response of examined mountain tunnels with PGV compared to PGA. To identify optimal IMs for bored tunnels in soft soil, Huang et al [56] tested the correlation, efficiency, practicality, and proficiency of 18 IMs, based on regression analyses between the IMs (estimated at free-field conditions) and the dynamic response of the examined tunnels (expressed through an EDP), computed via a series of full dynamic analyses. A better performance of PGA (referring to ground surface) was reported for the examined case of a shallow tunnel, whereas in the cases of a moderately deep or deep tunnel, PGV (at the ground surface) was found to be the optimal IM among the tested ones.…”