مقاله انگلیسی رایگان در مورد رفتار لرزه ای تونل آسیب دیده در طی پس لرزه – الزویر 2018

This paper studies the seismic behaviour of tunnels that are damaged during aftershocks. The tunnels were made from three different materials that had different flexural rigidity. An undamaged tunnel was constructed out of one material, while the damaged tunnels were built with the other two materials. The seismic load was applied with a unidirectional shake table. The peak ground acceleration for various input motions varied from 0.1 g to 1.2 g. The dynamic earth pressure around the tunnel was measured using three soil pressure transducers. The tunnel was placed in the transverse direction of shake table motion. The properties of the surrounding soils were calculated from bender element. The peak dynamic stress generated in the soil was used to study the behaviour of the damaged tunnels. A hand-held vibration analyser was used to measure the motion of the shake table. The results show that the damaged tunnel is more vulnerable to low frequency seismic motion.

Introduction

The demand for underground spaces has increased with the increased population. The underground structures were constructed mostly in mountainous region with hard rock strata and with little or few human population. However, during the last few decades, underground structures have been constructed beneath cities with large human populations living in densely packed buildings. Comparatively shallow cover and soft ground conditions make such structures more vulnerable. Thus, any damage to the underground structure beneath the city can cause severe damage to the surrounding structures and human lives. Therefore, the underground structures constructed beneath the city need greater safety and functionality during main shocks (MS) and aftershocks (AS). Aftershocks (AS) are very common phenomena observed after the MS and are believed to follow the Gutenberg-Richter Law. The randomness and large magnitude of AS have the potential to collapse structures damaged during MS. Most often, the larger MS are followed by larger AS [1–6]. Hence, this research focuses on the seismic behaviour of the damaged tunnel during AS. The severity of earthquakes to underground structures can be seen from the results of the Kanto earthquake, which occurred in year 1923 and damaged about ninety-three tunnels. Twenty-five out of ninety-three tunnels damaged in the Kanto earthquake had to be reconstructed. Also, the ground collapse resulted from lining damage. The Izu-Oshima-Kinkai earthquake damaged nine tunnels that crossed the fault line. The Kobe earthquake in 1995 caused the tunnel lining to fail under shear and compression. In a more recent Niigataken-Chuetsu earthquake in 2004, twenty-four tunnels were damaged. The tunnels near the epicentre (within 10 km radius) sustained heavy damage. Spalling of concrete lining was observed along with a reduction in the tunnel’s diameters [7]. The tunnels passing through rock were also damaged during the Niigataken-Chuetsu earthquake [8]. Dowding (1978) collected data about seventy-one (71) tunnels and found that the tunnels are vulnerable to damage only if the peak ground acceleration (PGA) exceeds 0.19 g. Furthermore, PGAs of 0.19 to 0.5 g are moderately damaging and PGAs of 0.5 g or more are heavily damaging [8]. Many researchers have reported that the sections damaged occurred during MS become more vulnerable during AS [9–12].