Simplified method for consolidation rate of stone column reinforced foundations

Field observations and numerical studies demonstrated that stone columns co uld accelerate the rate of consolidation of soft clays. A simplified method for computing the rate of consolidation is presented in this paper by assu ming that stone columns; (1) are free draining; (2) have higher drained ela stic modulus than soft clay; and (3) are deformed 1D. The formats of the fi nal solutions in vertical and radial flows are similar to those of the Terz aghi 1D solution and the Barron solution for drain wells in fine-grained so ils, respectively. Modified coefficients of consolidation are introduced to account for effects of the stone column-soil modular ratio. The new soluti ons demonstrate stress transfer from the soil to stone columns and dissipat ion of excess pore water pressures due to drainage and vertical stress redu ction during the consolidation. Comparisons between the results from this s implified method and the numerical study by Balaam and Booker in 1981 exhib it reasonable agreement, when the stress concentration ratio is in the prac tical range (2-6). The discrepancies in the results from these two methods are discussed. This paper also includes design charts and a design example.