All tunnels have complex cross section with circular, rectangle, arch, ellipse shape, in accordance with the length of the tunnel is divided into short, medium length of the tunnel, long tunnel.

隧道按截面分为圆形、矩形、拱形、椭圆等形状，按照长度分为短隧道、中等长度隧道、长隧道。

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TBM is commonly used for deep buried and long tunnels and becomes prevailing technique for tunnel excavation in international practices. The total length of No.

埋深大、线路长的隧洞采用TBM施工，已成为国际上快速开挖隧洞的主流。

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First conceived nearly one-hundred years ago during the reign of Russian Tsar Nicolas II, the BST would be the longest tunnel in the world - over twice the length of Europe's 30 mile long "Chunnel" linking Britain and France.

CENTERFORSECURITYPOLICY: The Bering Strait Tunnel Project