Co-seismic stress changes and damage to tunnels in the 23 October 2004 Mid-Niigata Prefecture earthquake

• Published in: Canadian geotechnical journal 2018-05, Vol.55 (5), p.736-748
• Main Authors: Kazmi, Zaheer Abbas, Konagai, Kazuo
• Format: Article
• Language: English
• Subjects: Deformation mechanisms; déplacement de sol; Earthquake damage; Earthquakes; fault slip; glissement de sol; ground displacement; Half spaces; Mid-Niigata Prefecture earthquake; Mountain tunnels; Railway tunnels; Sedimentary rocks; Seismic activity; Seismic engineering; Seismic response; seismic stresses; Soil; stress sismique; Tensors; tremblement de terre de la préfecture de Mid-Niigata; Tunnels; tunnels ferroviaires; Zonation
• ISSN: 0008-3674; 1208-6010
• DOI: 10.1139/cgj-2016-0658

Recent near-field earthquakes accompanied by large soil deformations have been clouding the notion that mountain tunnels would be safe places during earthquakes. One of the recent eye-openers was the damage to railway tunnels in the 2004 Mid-Niigata Prefecture earthquake. Changes in stresses in the interior of a half-space of stratified sedimentary rocks, as a representative of the earthquake-hit region, are obtained using the authors’ previous works on co-seismic deformations of this region to study the damage mechanism of deeply embedded railway tunnels. The values of square root of the second invariant of the stress deviator tensor, , and the first invariant of Cauchy stress tensor, , are compared with the reported damages along the entire stretch of selected tunnels and a very good correlation is observed between the peak values of and the damaged sections of the tunnels. A yield surface is defined as the boundary between clusters of points for damaged and undamaged tunnel sections in the scatter diagram of and . This yield surface and rock–soil deformability can be used to examine the margin of safety of both existing and new tunnels as well as for hazard zonation in a given scenario earthquake.