This paper presents results of experimental tests on soil specimens reinforced by stone columns. The experimental investigations have been conducted by setting up a laboratory scale model. The main objective is to evaluate the effects of various reinforcing materials and stone columns configurations on the axial deformation during a vertical loading test of cylindrical samples of unreinforced and reinforced soil. The findings have been compared to existing experimental results proposed in literature. The specimens of soil consisted in an analogic material of poly-dispersed glass beads with a grain size smaller than 50 µm. Two reinforcing materials have been considered as ballasts: crushed sand and coarser granularity glass beads (0.7-1.0 mm). The results show that the material type and spacing between columns in a triangular or square configuration can greatly affect the reinforcement efficiency. The proposed results are applicable to predict the improvement of granular soils of medium density when subjected to the vibrocompaction technique.