PURPOSE: To reduce earth pressure by providing a material contracted in acting compressive forth to the peripheral surface of a culvert.

CONSTITUTION: A material 2 contracted in acting compressive forth of foamed styrene resin, etc., is provided to the peripheral surface of a culvert member, and filling is executed. After that, a contraction member 2 is contracted by the action of earth pressure, the strain of the earth in a parallel direction with the peripheral surface of the member is increased, the stress of the earth in the same direction is increased to wrap the member 1 in the main stress of the earth and is distributed in the shape of an arch. Then, The stress of the earth at a right angle to the peripheral surface of the material 2 is reduced to minimize earth pressure acted on the material 2.