Soil improvement manner of bed and application manner of bed tunnel.

摘要

PURPOSE:To surely support the lower surface of a subaqueous tunnel with the heads of foundation piles by setting the height of the head parts of the foundation piles to be slightly lower than the height of the bottom surface of the subaqueous tunnel, and by excavating a part which surrounds the head parts of the piles and in which the foundation has been improved. CONSTITUTION:The heights of steel pipe piles 2 which have been driven into the submarine foundation with the use of auxiliary members are uniformly set to be slightly lower than the height at which the bottom surface of an excavator 6 passes. Then, casing pipes 3 are driven with the use of the auxiliary members as guides, and then the auxiliary members are withdrawn before sediment is discharged from the casing pipes 3, and then caps 4 are hung down so as to close the upper ends of the steel pipe piles 2. Thereafter, the foundation around the piles 2 are improved so as to form an improved layer 5 along which the tunnel excavator 6 is moved. The passage of the excavator 6 constructs the subaqueous tunnel, and since the bottom part of the subaqueous tunnel or the whole part thereof is positioned in the improved layer 5, the tunnel can be supported. Thereby it is possible surely support the tunnel even though the heights of the head parts of the piles 2 are inaccurate.