Numerical analysis of underground tunnels subjected to surface blast loads

Alaa Ata,Mahmoud Nawar,Marwa Nabil,Sally Hassan

doi:10.3221/igf-esis.55.12

Alaa Ata, Mahmoud Nawar + Show 2 more

Open Access

https://doi.org/10.3221/igf-esis.55.12

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Abstract

The increased terrorist attacks on important public structures and utilities have raised the vital necessity for the investigation of performance of structures under blast loads to improve the design and enhance the behavior of structures subjected to such threats. In this study, 3-D ﬁnite element analysis is used to study the effect of surface explosions on the response of RC bored tunnels. The soil behavior is modelled using Drucker-Prager Cap model. Two types of soil are investigated, and the blast load is considered through various weights of TNT explosive charges at heights of 0.50 m and 1.0 m from ground surface. To study the effect of horizontal standoff distance, six different horizontal distances are considered. The results show that the soil type has a significance effect on tunnel response due to surface blasts. Also the weight and the location of charge have a great effect on the safety of the tunnel. Finally, a parametric study is established to define the borders of the restricted area around the tunnel location to be safe.

Highlights

Blasts have a devastating effect on structures, as well as, human beings
A finite element model is developed to study the performance of underground tunnel under surface blast load
Two types of soils are considered with different TNT weights and different horizontal distances. the following conclusions are obtained: 1) The developed model is able to predict the pressure propagating into the soil with a fair agreement to the empirical equations

Summary

Introduction

Blasts have a devastating effect on structures, as well as, human beings. Blasts may affect humans by injury, health problems and loss of lives. When an explosive charge is near the ground surface, the super and shallow structures, foundations and shallow tunnels, are subjected to ground shock. When the charge is exploded near the ground surface, there will be two types of transmitted energy that cause ground shock. A part of energy goes directly through the soil causing a direct ground shock, while additional part is transferred through the air and compresses the ground surface and sends pressure into the ground under layers known as air-induced-ground shock [1]. If the explosion is directly above the surface, a conical-shaped crater is formed in the ground [2, 3]

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