| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of constructing a main tunnel by using a drilling machine at normal low water pressure while conserving ground water by performing water conveyance without performing complete drain. SOLUTION: A guide tunnel is excavated in a large depth and at high water pressure in parallel with the main tunnel and ahead of the main tunnel, and a headrace is provided by conducting borings from the guide tunnel. The headrace is formed in an umbrella shape from a cross-sectional view where it covers the top of the main tunnel. Then the ground water positioned at the top of the main tunnel is discharged from the headrace, and a low water pressure block 4 is formed under the umbrella-shaped headrace, The main tunnel is excavated by the conventional construction method of a tunnel in a state where the main tunnel penetrates the low water pressure block. COPYRIGHT: (C)2010,JPO&INPIT
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