PURPOSE: To artificially suppress the reaction of the ground by easily controlling the end support pressure of dam by a method in which the counter of filling soil and sand is placed in the inside of housing portions on the front, back, and both sides of a block structure.

CONSTITUTION: A block structure S consists of side plates 4 constituting a vertical partition wall 1 and housing portions 5a and 5b, sheathing plates 3, a bottom plate 2, and a partition plate 6. When constructing a dam, a mound 8 is constructed on the ground and the structure S is settled on the mound 8. In case where tidal wave comes from the seashore, the housing portion 5a is embedded with soil and sand or rubble to equalize the end support pressure of the structure S. Also, when no tidal wave exists, the housing portions 5a and 5b on both sides are filled with soil and sand, etc., to equalize the end support pressure of the structure S. Then, the back side of the partition wall 1 is embedded. By controlling the amount of filling soil and sand for the housing portions 5a and 5b, the end support pressure of the dam can be equalized.