Experimental investigations on the influence of embedment depth and frequency on the dynamic behaviour of tunnels under repeated shaking events

Abstract

ABSTRACT Recently, occurrence of repeated shaking events such as the Kobe earthquake (1995), the Wenchuan earthquake (2008), the Chi-Chi earthquake (1999) and the Kumamoto earthquake (2016), Kahramanmaras earthquake (2023), etc., posed a severe threat to the safety of infrastructures. Studies on the influence of repeated shaking events on underground structures are minimal. Considering the above, tunnel-soil interaction under repeated shaking events is attempted in the study. One-gram shaking table tests were conducted in this study by varying loading frequency (5 Hz, 10 Hz) and tunnel embedment depth (H/W − 0.85 and 1.2 where H is the tunnel embedment depth and W is the width of the tunnel) and subjected to incremental shaking conditions, i.e. 0.2 g, 0.3 g and 0.4 g. A tunnel-embedded ground with 60% relative density was prepared and instrumented with conventional sensor schemes and a non-contact-based 2D digital image correlation technique. It was observed that the loading frequency and tunnel embedment influences tunnel’s performance during repeated shaking events. About 37% to 62.4% increment in tunnel displacement was observed in the case of H/W-0.85, and 20% to 29% increment in tunnel displacement was observed for H/W-1.2 when subjected to incremental acceleration shaking, i.e. 0.2 g to 0.4 g for varying embedment depth conditions.