Improve Geotechnical Design Parameter of Some Soft Clayey Soils

The shallow Soft Clayey deposit is common in Alexandria-Egypt. Most soft clays in their natural state are unsuitable for supporting any structure. Thus, improvement treatments exist to strengthen these soils so that improved soil can have adequate bearing capacity without undergoing failure or producing substantial excessive settlement post construction and applied loads to them. This paper presents a case study of an improved site in the city center, which reclaimed part of Maryout Lake, where the highly compressible clay with water content varies from 200% near the surface to 90% at the base of the shallow clay deposit. A prefabricated vertical drain with preloading has been used to improve this soft soil. Values of shear parameters and consolidation coefficient back-calculated from field measurements and have been compared with the values from lab and in situ tests. The study provides different relationships from comparisons of prediction and estimation compressibility and consolidation settlement from laboratory studies and particularly field case studies. Also, some correlation related to the compressibility with index properties of soft clay is presented. The results display that a substantial improvement is noticeable in the compressibility properties.