A New Analytical Formula for Estimation the Bearing Capacity of Stone Column Group in Soft Soils

Stone columns are a well-known, effective, and efficient method for increasing the bearing capacity of soft soils. The most common application is in the form of a group of stone columns. A simple analytical formula is necessary to estimate the bearing capacity of a group of stone columns. In this study, the problem's geometry is simplified by first homogenizing the soil and stone column, then applying the imaginary retaining wall method to evaluate the ultimate bearing capacity of the stone column group. The proposed analytical approach requires the Mohr–Coulomb shear strength parameters of the stone column material and soft soil, the area replacement ratio, and the stress concentration ratio to estimate the ultimate load-bearing capacity. The bearing capacity is verified against laboratory test data and numerical simulations. Comparison of the analytical formula with numerical results shows an average difference ranging from + 4 to 25%. When compared with experimental data, the difference ranges from − 21 to + 24%, with an average variation between − 5 and 8%. Design steps and a practical example are also provided.