Effect of sand columns on the drained load response of soft clays

Abstract

Compacted sand columns constitute an economical and environmentally friendly technique to treat and reinforce weak soils to increase their load-carrying capacity and to allow the soil to support loads from overlying structures. This method has been used for almost 30 years to improve the quality of both fine and coarse grained soils by increasing the bearing capacity, accelerating consolidation and improving the settlement response of the foundation. The extent of improvement depends on the confinement ensured by the surrounding soil, the presence of reinforcing material around the columns (geosynthetics) and the properties of the sand columns. The inclusion of geosynthetic reinforcement enhances load transfer from the soil to the columns and reduces total and differential settlement. The objective of this thesis is to study the performance of clay specimens that are reinforced with sand columns of different diameters, heights, and confinement conditions and which are loaded under fully drained conditions to represent long-term stability conditions. The study is comprised of a series of triaxial tests that will be performed on back-pressure saturated normally consolidated Kaolin specimens that are prepared from slurry. The parameters that are varied in the study are the diameter of the sand column (2cm and 3cm), the height of the column relative to the height of the clay specimen (0.75 and 1.0), and the type of sand column reinforcement (no sand column, unreinforced sand column, and sand column reinforced with a geotextile). All tested samples will be consolidated and tested at confining pressures of 100 kPa, 150 kPa, and 200 kPa to study the effect of sand columns on the load response of soft clays.