In the practical design of stone column for soft soil improvement, the stress ratio between stone column and soft clay has been largely calculated based on the surface stresses. The vertical stress and pore pressure changes in the surrounding soft clay have not been adequately measured and compared with column stresses in the past research works. Similarly, the influence of the morphological properties of column particles on these stresses has been largely overlooked in the practice. As part of the laboratory testing programme, onedimensional consolidation tests were carried out on a unit cell which comprised of soft kaolin clay and stone column. A number of tests were carried out by varying the morphological properties of column materials such as the particle size distribution and particle angularity. Miniature pressure and pore-pressure sensors were placed at various locations including in the proximity of anticipated bulging location where the column stress was relatively high. The results showed that stress ratios between column and clay at the same depth within the unit cell were influenced by the morphological properties of column materials. Moreover, it was generally observed that stress ratio of a unit cell under sustained loading did not only vary with time but it also varied with the depth.