Estimation of bearing capacity of floating group of stone columns

Stone column is one of the ground improvement techniques. This technique has a proven performance, short time schedule, durability, constructability and low costs. The stone column technique has been used as a method of reinforcement of soft ground over the past 30years. The bearing capacity of the stone column still has high level of uncertainties because the existing formulas for the estimation of the bearing capacity are general and do not take into consideration the type of the stone column whether if it’s floating or end bearing and the method of the implementation of the stone columns and the length to diameter ratio of the stone column (L/D) and many other factors that affect the bearing capacity of the stone column. In the present study, a general equation was obtained by carrying out statistical analysis using the SPSS (Statistical Package for the Social Sciences) program from the present experimental work and previous studies. The equation is used to estimate the bearing capacity of floating stone column group installed in clays of different undrained shear strengths between (4–25)kPa and with different diameters and L/D ratios constructed by cased bored method. The equation indicates that the most controlling parameter in the prediction of stone columns bearing capacity, qu, is the area replacement ration, As, where qu increases considerably with increase of As, i.e. decrease of spacing between columns.