| 摘要 |
PROBLEM TO BE SOLVED: To stoop down an unexcavated area on the existing tunnel side in a heading method to be excavated even when the peripheral natural ground is softened. SOLUTION: In a flat semicircular tunnel section containing the section of a newly-constructed tunnel 2 and the section of an existing tunnel, the space of a quarter of the section on the newly-constructed tunnel side is first excavated, a steel timbering 20 is installed, and the end thereof is fixed to the natural ground. After that, an unexcavated area M on the existing tunnel side is stooped down to be excavated above the finally provided timbering structure installation surface by a heading method, and a temporarily provided steel timbering 50 is erected to be fixed by shotcrete. After that, the peripheral natural ground where the end 27a of the newly provided steel tembering 27 collides is improved and reinforced, and the space up to the finally provided tembering structure installation surface SA in the space in a pilot tunnel is filled with shotconcrete. After that, the finally provided steel tembering 27 is extended to finish the finally provided tembering structure, and the lining concrete 25 on the existing tunnel 1 side of a part, the need of which is removed by the junction to the newly provided tunnel is knocked and removed. |
