The study of the coefficient of horizontal subgrade reaction, that is k-value, has been performed in the 3-dimensional ground, such as the load test of pile or the load test in the boring hole. The value of the coefficient of horizontal subgrade reaction in the 2-dimensional ground, however, has lately been required in the field of the design of the sheetpile quay which must be constructed on the soft clay.
　In this report, the auther inferred 3-dimensional k-value by using both the Louis Menard's approximate formula of lateral displacement and 3-dimensional F.E.M. This inferred value agreed rather well with actual measurement value. The same method was applied to the 2-dimensional k-value, and the auther showed both the relation between k-value and cohesion Cu in the clay ground, and the relation between k-value and N-value in the sandy ground.