Evaluation of Distinct Factor Affecting the Bearing Capacity in Ground Improvement with Stone Column Group

Increasing construction industry and the need to build structures on lands that do not have sufficient load-bearing capacity resulted in the development of soil improvement techniques to enhance site capability. The use of stone columns for the ground improvement for reasons such as environmental compatibility, cost effective, minimizing the liquefaction potential of the ground, settlement reduction, increase of the load-bearing capacity and significant reduction in the period of consolidation is considered as one of the most effective soft soil reinforcement methods. Stone columns can be designed to bear on the hard stratum or as a floating system where the toe is embedded in the soft layer. What in recent years were as the basis for designing of groups of stone columns were based on the theories developed for single stone columns ignoring the group interaction. Most of the existing design methods for stone columns adopt unit cell idealization which is not applicable to spread footing. To assess the influence of various parameters on the performance of a group of stone columns, in this paper which is based on the finite element method, the effect of hardness and resistance parameters affecting the load bearing capacity was discussed. More than 140 analyses of different parameters of soil and stone columns were carried out and were discussed in the form of graphs to compare the effects of these parameters. Results showed that using stone columns had a significant impact on increasing the bearing capacity of the soft grounds. The rate of growing enhances with increase of replacement ratio of stone columns into the soft soil due to group interaction. Increase of elasticity and internal friction angle of column materials as well as soil Poisson's ratio have a significant impact on increasing load-bearing capacity on the other hand when Poisson's ratio of stone columns increases any substantial change isn’t see. In addition of bearing capacity increase, growth of replacement ratio enhances the impact of strength and stiffness parameters of soil and columns on bearing capacity increase which shows the influence of the group interaction. End bearing columns were observed as a factor influencing the increase of bearing capacity and intensifying the effect of stiffness and strength parameters on column bearing capacity.