Behaviour of geosynthetic-encased granular columns in porous collapsible soil

Abstract

ABSTRACT: The construction of embankments on soft saturated soils can be a challenge due to the low shear strength and high compressibility of these soils. The same may be true for constructions on porous collapsible soils, because the collapse of the soil structure can lead to large foundation soil deformations leading to damage to the embankment, particularly in the case of bridge abutments. Conventional piles and granular columns have been used to stabilize such embankments when there are limits for embankment settlements. More recently, geosynthetic-encased granular columns have been increasingly used as an alternative solution. This study examined the performance of geosynthetic-encased columns for the stabilization of embankments on porous collapsible structured unsaturated soil. Field load tests were performed on conventional sand and gravel columns and on geotextile-encased sand columns and on geogrid-encased gravel columns. During testing, the collapse of the surrounding soil was induced by water injection through the granular column top to investigate the influence of the casing on the column performance. The results obtained show that significant increases on pile load capacity can be obtained depending on the materials used and construction conditions. The effects of foundation collapse can also be reduced with the use of a geosynthetic casing in the granular column.