Seismic Behaviour of Urban Underground Structures in Liquefiable Soil

Soil liquefaction has been often one of the most significant causes of damage to aboveground structures in urban areas during recent earthquakes, e.g. 2012 Emilia (northern Italy), 2011 Tohoku Oki (Japan) and particularly 2011 Canterbury-Christchurch (New Zealand), where about half of the e25 billion loss was directly caused by such a phenomenon. In some cases, sewer pipes or open-cut tunnels in liquefied deposits have been affected by floatation and large uplift. The current and future construction of relatively shallow and light underground structures in seismic regions may involve areas that are exposed to the risk of liquefaction thus increasing possible associated damages. This paper investigates the behaviour of a tunnel during soil liquefaction, from an experimental and numerical point of view, focusing on the combined effects of soil liquefaction in urban areas, where underground structures are likely to interfere with buildings. Such an aspect is rather unexplored, and the research in this field may contribute to the performance-based design of urban underground facilities.