Column Group Analyses for Stone Column Reinforced Foundation

Stone column reinforced foundation has gained popularity as an effective ground improvement technique available in practice. The design of large group of columns is normally done assuming infinite columns grid under a wide loaded area (i.e., unit cell concept). However, the design for small column groups is often approached empirically due to the lack of research on this issue. This study is aimed at investigating the behavior of small column groups by establishing the relationship between the number of columns and the settlement improvement factors. Two-dimensional (2D) concentric ring approach is adopted. This 2D approach is validated by comparison with a three-dimensional model before being used subsequently for detailed analyses. From the results, the optimum length for the columns group is determined where further lengthening of the column provides no further improvement for the system. Simple design method is suggested for rigid spread footings supported by small column groups, and the comparison is made to the settlement performance obtained from the unit cell concept.