PURPOSE: To exhaust the ground-water smoothly by providing drain holes through foam styrene members to be buried under concrete blocks which are buried in the soft ground, and inserting connecting pipes into them.

CONSTITUTION: Drain holes 6 are provided in the longitudinal, the lateral and the vertical directions of a foam styrene body 4 formed into a block having a constant thickness, and short cylindrical connecting pipes 7 are inserted to it so as to connect the foam styrene bodies 4 positioned in front and rear thereof. Next, the foam styrene bodies 4 are laid through a sand layer or a crusher run layer 3, and concrete blocks 1 are placed thereon through a crusher run layer 5 to provide a channel 2 to be buried in the soft ground A. Snaking and lateral dislocation of the foam styrene bodies 4 are thereby prevented, and the ground-water is discharged smoothly, and the channel 2 to be buried is held stably.