There are essential differences between the composite grounds improved by stone columns and by rigid piles,such as reinforced concrete piles,steel-pipe piles and other rigid piles.The voids of the stone columns can act as vertical drainage channels and accelerate the consolidation of the surrounding soft soil resulting in the improvement of the ground strength.Meanwhile,the improvement effect of the stone column depends directly on the lateral support of the surrounding soil.How to accurately determine the overall shear strength of stone column-soil composite ground is the key task to make full use of stone columns.Taking Hong Kong boundary crossing facilities-reclamation works for example,we compare different calculating methods for the overall shear strength of the composite ground,and carry out some analyses of the parameters using the finite element analysis and in-situ monitoring.This study has significant effect for the calculation of overall shear strength of the composite foundation under similar conditions.