PURPOSE: To raise the efficiency of draining from soft ground by providing a small-diameter tube having a high pressure resistance against consolidation loads and a high flexibility, and also having large numbers of small holes in its periphery into a sand pillar formed in the soft ground in such a way as to insert it longitudinally into the sand pillar.

CONSTITUTION: A pit 2 is drilled in soft ground 1, and a sand pillar 3 protected with a water-permeable bag 6 is formed in the pit 2. A flexible small-diameter tube 7 having large numbers of small holes impervious to sand on its periphery and also having a high pressure resistance against consolidation pressure is longitudinally inserted into the sand pillar 3. A sand layer 4 and a banking 5 are formed on the ground. The water discharged from the soft ground 1 by the load of the banking 5 goes into the small-diameter tube 7 through the sand pillar 3 and then is discharged through the tube 7 to the ground's surface.