Model pile loading tests in dry sand were conducted with applying confining pressure of 50-200kPa at the surface of
the model ground to investigate the behavior of a group pile. The group pile consisted of 9 cylindrical model piles of 40mm in
diameter, while two kinds of the pile spacing between pile centers were used; 2.5 times of the diameter of the pile and 5.0 times of
the diameter. For comparison, a single pile with a large diameter was also tested under the same condition. The test results were
discussed based from the following 4 points of view; the settlement at the yielding point of the total load, tip stress distribution by the
pile location in the group pile, pressure distribution in the soil measured by the tactile sensors and ground deformation after the
loading tests. All discussion suggested that the group pile of 2.5D spacing caused significant interactional effect between piles and
behaved in one block. In contrast, each pile in the group pile of 5.0D spacing behaved more individually