ABSTRACT
For shield tunnels, seismic isolation layer is an effective countermeasure to reduce structural damage during earthquakes. In this paper, the physico-mechanical properties of asphalt-cement (A-C) materials applied to backfill grouting of shield tunnels were investigated by laboratory tests. Then, fragility curves were developed by analytical approach for shield tunnels before and after setting three typical A-C isolation layers (i.e. A-C Iso-layer1, 2, and 3), which were used to express the seismic vulnerability of tunnel lining and evaluate the seismic-reduction effectiveness under earthquakes. The results reveal that A-C isolation layers are effective in seismic-reduction under excitation of low input intensity (less than 0.5 g), while its effect is not significant at high-input intensity. The fragility curves for tunnel lining after setting A-C isolation layers show less vulnerability than not setting one at all seismic intensity levels. From the perspective of damage probability, the seismic-reduction effectiveness decreases with the increasing shear modulus of A-C isolation layer. The probability of minor damage of examined tunnel lining setting up with A-C Iso-layer1 decreased from 23% to 15% at most.
Acknowledgments
The authors are grateful to anonymous reviewers for their valuable and most helpful comments.
Disclosure Statement
No potential conflict of interest was reported by the author(s).