A fire broke out on a freight train yesterday as it traveled the Channel Tunnel, which links England to France. Fortunately, all passengers were escorted to safety, though some suffered injuries. How are tunnels constructed?
A tunnel can be simply defined as a tube hollowed through soil or stone, but actually constructing a tunnel is a complex task. While some are hailed as technological masterpieces, others suffer major setbacks. Learn how tunnels are built and examine an ongoing tunnel project that continues to make headlines -- Boston's "Big Dig."
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