PURPOSE: To prevent the liquefaction of the ground when earthquake occurs by a method in which gravel drain of gravel columns is provided in the sandy ground, the area from the upper end of the drain to low-water level at low tide is covered with a clogging preventive water-permeable tube, and gravel mat is laid on the drain.

CONSTITUTION: Gravel drain 1 consisting of gravel columns is set in sandy ground 2, and the area from the upper end of the periphery of the gravel drain 1 to the position about 30cm below the water level L.W.L at low tide is covered with a water-permeable tube 4 of vinyl chloride. Gravel mat 3 is laid on the gravel drain 1. The clogging of the gravel drain when earthquake occurs can thus be prevented and the liquefaction of the ground can be prevented.