Eexperimental study on Equivalent shear strength of cohesive soils improved with Stone columns by Triaxial Testing

The use of stone column is an effective method in modifying of poor soils. One of the methods of studying the behavior of soils improving with stone columns is homogenization method. In this method, the stone column and the surrounding soil are replaced with a homogenous soil. In homogenization method the equivalent parameters are calculated by means of weighted average of soil and column parameters with linear relations. In this study, equivalent shear strength and shear strength parameters of the soil improved with stone columns was calculated based on the analytical relationships and the accuracy of the relationships used was evaluated through triaxial tests. In this study with help of simulation of the unit cell in the laboratory scale and investigating the shear strength of soil improved with stone columns, behavior of stone columns was investigated. The laboratory experiment consisted of series of the triaxial tests with a diameter of 100 mm and height of 200 mm and sand column with diameter of 37.5 and 51 mm and 3 confining pressure 50,100,200 kPa. The results of this study shows that with the use of a stone columns in soft soil, the undrained shear strength and the stiffness of the sample is increased and with increased confining pressure, the percentage of undrained shear strength increased. The difference between shear strength parameters obtained from experiments and those predicted by analytical relationships with the increase in the stress concentration ratio increased and decreased with increasing undrained shear strength of the surrounding soil.