| 摘要 |
PURPOSE:To improve safety and strength of the cavity part by standingly providing a cylindrical part along the center axis of a large cavity project territory under ground, constructing a rectilinear tunnel in the radial direction from the lower end side of the cylindrical part, further constructing a curved tunnel along the circumferential direction, and repeating these processes. CONSTITUTION:A vertical shaft 1 of small diameter is drilled up to the upper part of a large cavity part 2 project territory, and the inner circumferential face is given lining 3 in order. Nextly, necessary equipments, materials, and workers are brought in from the ground by use of the vertical shaft 1, and the bottom part part of the vertical shaft 1 is conically drilled to provide a spread drilled part 4 and given a lining 5 connected to the lining 3. Further, a cylindrical pipe 6 is buried and provided on the foundation of the spread drilled part 4 up to the lower part of the large cavity part 2 project territory. A part of the cylindrical pipe 6 is cut off and a rectilinear tunnel is drilled in the radial direction, and sequentially a curved tunnel of respective half circumferences are drilled along the circumferential direction. Hereafter, by repeating these works, a cylindrical outer circumferential wall 28 is constructed, which is continued to the planned upper part of the large cavity part. |
