Assessment of Underground Structure–Soil Interaction Under Dynamic Conditions

Abstract

Recently, underground structures constitute a vital component for transportation systems. Despite of its wide selection for infrastructure development, experimental studies related to dynamic assessment of these structures under dynamic conditions were limited. This was mainly due to improved confinement characteristics offered by the soil or rock with underground structures. However, underground structures experienced significant damages in recent earthquakes, i.e. 1995 Kobe, Japan earthquake, the 1999 Chi-Chi, Taiwan earthquake, etc. This justifies the need and importance for understanding the behaviour of tunnels under dynamic conditions. In India, 1489 tunnels spanning 4144 km are in various stages—under implementation, awarded, under bidding, approved, planned/proposed and in construction. Also, according to recent survey, northern part of India, i.e. Jammu and Kashmir and Ladakh, would likely to have 6 tunnels which lies in major seismic prone areas. Considering the safety of tunnel systems, this paper addresses the factors influencing tunnel–soil interaction under dynamic conditions. 1-g shaking table experiments were conducted with scaled down tunnel model installed inside ground having 60% density. The experimental tests were performed with repeated incremental 0.3 and 0.4-g acceleration loading conditions simulating repeated occurrence of earthquake shaking in real conditions. The dynamic behaviour of tunnel–soil interaction was evaluated in terms of acceleration response, dynamic soil pressures. The maximum tunnel displacement and strain development also assessed using DIC technique. Finally, this study presents the factors contributing tunnel deformation, especially under repeated incremental shaking events.KeywordsUnderground structuresTunnel–soil interaction1-g shaking table experimentsDigital image correlation (DIC)