Abstract: A research program of strengthening of saturated silty soils by vibro replacement stone columns was conducted, including measurement of dynamic pore water pressure during each stage of vibroflotation, such as stage of inserting vibroflot, dissipation of pore pressure after sinking down to the design depth, effects of repeated vibroflotation and the stage of forming stone column, and some parametric analysis. Wave velocity method for determining effectiveness of densification of vibroflotation and some comments are presented.