Finite Element Analysis of Embankment Supported by Stone Columns in Soft Clay

Abstract

A finite element computer program model for analysis of soil stone column-system in soft clay is developed. The model has the capacity to represent the linear and non-linear behavior of both constituent materials (soft clayand gravel). Settlement predictions of the computer program were compared with the previous published results and existing field results from New White Nile River Bridge in Sudan. The predictions of the computer model were in good agreement with other models and field measurements. The program can be used to find the bearing capacity of the soil stone column system .The program also can be used to find the distribution of the vertical and horizontal stresses and the shear stresses on the columns. Parametricstudies were conducted to study the parameters, which have profound effect on the performance of the system. These studies showed that the settlement of the soil stone column-system decreases with increase in column diameter and increase in diameter spacing ratio. Spacing ratio greater than 0.4 (i.e. spacing > 2.5 *diameter) is inefficient in designing stone columns. Also depth ratio greater than 0.5 is ineconomical in designing stone columns when the soft clay layer is thick. The study showed that higher degree of compaction of stone column material has a profound effect on settlement reduction. The bearing capacity of the stone column soil system is found to be significantly higher than the bearing capacity of soft soil alone. It is found that the vertical stresses in the columns are significantly higher than in the soil, and is practically constant with depth exceptat the top and bottom where it decreases slightly. And the distribution of the vertical stress increases from the toe towardthe centerline of the embankment. It is also found that the horizontal stress is high at the top of the column and decreases down to a depth of 0.1L before it increases again with depth