Rapid Load Testing of Stone Columns

Stone columns are an economic solution for improving the bearing capacity of shallow foundations on soft soils. A novel impulse load test was developed and used to quantify the load-displacement response of shallow foundations on stone columns at a clay site. The testing methodology used is the rapid plate load tester. Static and dynamic tests were conducted on a 2 m x 2 m footing supported on slightly overconsolidated clay reinforced with stone columns and the results are presented. The stone columns were 6 m deep and constructed using the dry method at different area replacement ratios by varying the spacing and diameter of the stone columns. Static and dynamic field tests were performed to target loads of 2000 kN and equivalent bearing pressures of 500 kPa. Displacement time histories were acquired by both photocells and accelerometers. The unloading point method was used to derive an equivalent static load settlement curve for the footing on clay soil both prior as well as post improvement. The derived static curves show good correlation with measured load settlement curves in the static mode.