The elastic settlement of foundations and other structures, bases and subbase layers of paved and unpaved highways, and runways of airports is an important consideration in the design and construction process. Laboratory and field studies have shown that geogrid can be used as a reinforcing material in granular soil to increase the stiffness of the soil-geogrid composite system and thereby reduce elastic settlement. This implies that the modulus of elasticity of the soil-geogrid system is increased due to reinforcement. In order to evaluate the modulus of elasticity of the granular soil-geogrid composite in the field, cyclic plate load tests were conducted at a site at the Incheon International Airport (Korea) during its construction phase. The test results and the method for obtaining the modulus of elasticity are presented in this paper.