| 摘要 |
PURPOSE: A tunnel expanding construction method is provided to expand a tunnel on an existing tunnel without limiting the traffic. CONSTITUTION: A ground reinforcing layer(2) is formed around a tunnel(5) to be expanded by one of existing reinforcing methods. While an existing tunnel(1) is surrounded with a tunnel excavating device(4) of which inner diameter is larger than the outer diameter of the existing tunnel and on which both lower ends caterpillars(3,3') are installed, the tunnel is excavated. An evacuating safety guard of which outer diameter is smaller than the inner diameter of the existing tunnel is placed inside the existing tunnel. Thereafter, the existing tunnel is removed. Therefore, the tunnel is expanded without limiting traffic.
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