PERFORMANCE OF GRANULAR COLUMNS IN SOFT CLAY

Abstract

Granular columns are frequently used in soft soils to increase the bearing capacity of soft soils, to reduce the settlement, and to accelerate the consolidation. The soil-column interaction depends on several parameters, such as the stiffness of the column material and of the soft soil, loading rate, area ratio and the drainage conditional for both column and soft soil. The main purpose of this study was to investigate the effect of the area ratio and the drainage conditions on the behavior of soft soil reinforced by granular columns. A modified triaxial cell was used in the project so that trivial compression tests could be perform on the 100 mm composite specimens. Four different area ratios (the ratio of the area of the column to the area of the unit cell) were investigated, a=0.14, 0.25, 0.75 and 0.86. Two series of tests were performed for both drained and undrained conditions. The test results showed that the ultimate bearing capacity of the granular columns depended mainly on the lateral confining pressure that can be mobilized in the soft soil around the columns. The reduction of the compression of the composite specimens increased with increasing area ratio.