In order to satisfy the similarity of scales between model and prototype of foundation structure, the test equipments using hydraulic gradient method were developed, and the results of load tests on model piles performed by the test technique were reported (e. g. Zelikson, 1969; Taito, 1977; Shimazaki, 1978). The hydraulic gradient method is used to create artifical gravity (increasing of unit weight) inside porous media like sand. In their tests, however, it is apprehended that the friction forces are caused on the inner surface of test cylinder and uniform distribution of unit weights is not created within sand.
This paper presents the data of fundamental test on the effect of the above friction force and the results of test reducted the friction resistance by using the layer of teflon sheets and silicon grease. These experimental data are compared with analytical results from finite element method. The ratio of horizontal to vertical effective stress within sand measured during the tests are also discussed.