I. Hosseinpour

Strength and Compressibility Characteristics of a Soft Clay Subjected to Ground Treatment

The compressibility properties, undrained shear strength, and stress history are essential for reliable calculations of settlement and bearing capacity of soft soils. However, it is sometimes a challenge to determine representative parameters for very soft and high plasticity clays, which are often found in Brazilian coastal areas. In this study an extensive site investigation was planned aiming to interpret the behaviour of a trial embankment on stabilized soft ground. The site investigation was carried out in a test area located in the west of city of Rio de Janeiro, consisted of three clusters in which standard penetration tests, vane shear tests, and piezocone tests (CPTu) were performed. A number of correlations was developed and compared with empirical equations in order to verify their reliability. The results of these tests made it possible to define geotechnical parameters of the soft clay to use in the numerical and analytical computations of the embankment on reinforced ground.

Embankment on Encased Columns: Numerical Study of the Influence of Working Platform on the Development of Geosynthetic Basal Reinforcement and Encasement Tensile Forces

conventional stone columns are widely used to improve soft soils in which high compressibility and low shear strength are observed. In very soft soils, granular columns may undergo excessive bulging due to lack of lateral support provided by the surrounding soil. Wrapping the granular columns with appropriate geosynthetic material can reduce the total and differential settlements while improve the load carrying capacity of the composite ground. Using a compacted sand or gravel mat (known as working platform) placed below the embankment in common to prevent excessive lateral deformation of the foundation soft soil. In the circumstance of very high applied load, this granular mat may be further reinforced with a geogrid layer to enhance its effectiveness and to control the overall stability of the embankment. This paper presents the results of a series of three-dimensional numerical analyses performed to study the development of hoop forces in geosynthetic encasement under different combinations of working platform thickness and horizontal geogrid stiffness. The results showed that for a constant working platform thickness the hoop forces increased with the height of the embankment. The maximum values of the encasement hoop forces were also observed to reduce significantly as thickness of the working platform increased