Explosives have been used for tunneling for centuries [1,2]. Since the 1960s they have, in many cases, been replaced by mechanical methods (TBMs in particular), due to quicker advancement in favorable conditions, less effect on the environment and controlled overbreak or extra profile, which is less than that caused by explosives. However, mechanized systems also have some negative characteristics, such as the requirement that the shape of the tunnel be circular, the utilization coefficient of the machines is reduced in cases of poor tunnel stability, the high investment costs of the machines and the long setting up and dismantling times hinder their economic use in short tunnels. Furthermore, in large-diameter tunnels, TBM cannot achieve the same rate of advancement as in small or medium diameter tunnels. In poor quality ground, the overbreak caused by the machine is of the same order of magnitude as that caused by explosives. All these factors contributed to making excavation with explosives still the most widely used method in non-circular or larger section tunnels.
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