By analyzing the mechanical characteristics of the middle-wall, the style of the base of the middle-wall is put forward for the structural stability of the twin-bore connection arch tunnel.

通过对中墙力学特性分析，提出了有利于连拱隧道结构稳定的中墙基底样式。

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Construction began on the twin-bore tunnel in January 2007.

BBC: Hindhead Tunnel

The twin-bore Sasago tunnel is an estimated 4.3km (2.7 miles) long and is on one of the major highways out of Tokyo.

BBC: Japan Sasago tunnel: Collapse traps cars