Stone column, one of the ground improvement techniques, was developed for the substitution of sand compaction piles. Stone column is being used for not only accelerating consolidation but also increasing bearing capacity of loose sands or soft clay grounds. Although the merit of stone column, compared with sand compaction piles, is not drainage but reinforcement, the research on the stone column as reinforcement is insufficient. Therefore, in this paper, in order to observe the characteristic of stone column as reinforcement by laboratory experiments, the stress distribution characteristics which is one of the important factors to estimate the settlement reduction are studied.
The experiments are composed of five cases. In three cases, three test ground are formed in the steel drum. Then, each of the stone columns having the same particle size and distribution is installed. On the other hand, in two cases, test grounds having the same stiffness are formed in the steel drum and each stone column is installed with different size and distribution. Then, the Test ground is pressed by a static load with equal strain condition and stresses in the stone column, stresses in the ground, the settlement and excessive pore water pressures are measured. The results obtained from the experiments are compared with the results estimated by the modified Baumann and Bauer`s equation. Numerical analyses are also carried out to investigate the effect of stone column`s replacement ratio on the stress distribution characteristics.
