Experimental evaluation of stress concentration ratio of soft soil reinforced with stone column

Ground improvement using stone column reinforcement is an effective treatment technique to increase the stiffness and reduce the total and differential settlement of the soft deposits. Even though stone column reinforcement is a well-established technique, detailed experimental study regarding the load-sharing characteristics and parameters influencing the stress concentration ratio (SCR) between the soil and column is very limited. In the present study through a systematic laboratory investigation, time-dependent and peak SCR between the stone column and surrounding soil has been evaluated for a practical range of stone column, surrounding soil, top sand blanket thickness and column material properties. Stress experienced from the foundation loading to stone column and surrounding soil in a unit cell has been measured using earth pressure cells. Peak SCR has been observed to be in the range of 4–6 for the set of material parameters investigated in the present study. Peak SCR is in the range of 4–5.5 when internal friction angle of the stone column material varies from 38° to 42°. SCR is significantly influenced by the thickness of the top sand blanket. However, an insignificant influence of sand blanket material properties on the SCR has been observed. Additionally, surrounding soil strength significantly influences the SCR of the composite system. The results of the present study will be useful for the estimation of stiffness and settlement of the stone column-reinforced composite ground.