An Investigation on Stability of Clay Ground Improved by Sand Compaction Piles

A series of centrifuge tests was conducted in an attempt to study the effect of the weight of a caisson and the width and the area ratio of improvement by sand Compaction piles(S.C.P.) on the stability of improved ground under a backfilled caisson. Following conclusions are derived from this study. l.Horizontal deformations are much more dominant than vertical deformations when a backfilled caisson is built on soft clay improved with S.C.P. 2. For improved ground, a well-defined circular slip surface is observed. However for improved ground, horizontal deformations increase gradually with the increase of horizontal load and at a certain load the horizontal deformations suddenly start to increase, showing no slip surface in the ground. This leads to a conclusion that consideration of horizontal deformations is more important than that of stability against failure for this type of structure. 3. When the safety factor calculated by the modified Fellenius' stability analysis exceeds 1.4, considerable horizontal deformation appear. This leads to a conclusion that the minimum safety factor for this type of problem should be taken as 1.5.