The full-scale model test on coefficient of friction between a block of foam-treated soil and the base soil was carried out in Kumamoto Port. As the large volume of intrusion of foam-treated soil into rubble stones were observed in the test, the permeation behavior was studied in the laboratory model tests. The results of tests were summarized as follows:
1) The friction between the foam treated soil block and the base soil is determined by the internal frictional angle of base soil.
2) The frictional angle of uncompacted sand mat was 25°ー29°. To take the coefficient of friction recommended in the technical code, the compaction of sand mat is necessary.
3) The coefficient of friction between a block and the base of rubble stone was 1.69- 1.83. These large coefficients were apparent values, obtained due to a large volume of permeation of foam-treated soil into the rubble stones. In the design the use of the frictional angle in the stones can be recommended.
4) The volume of permeation of foam-treated soil in the rubbles is determined by the particle size (or voids between the particles) of rubbles and the flow value.. To prevent the permeation, the particle size of stone should be less than 40mm, or the flow value of the foam-treated soil placed on the stone should be reduced.