Consolidation of clay-granular medium composites

The thesis deals with the study of soil composites that are constructed by combining regions of soft clay and granular materials in various spatial configurations. The underlying basis for the work stems from the practical application of the results of the research to offshore land reclamation practices. Due to depletion of local coarse-grained soil sources and the high cost of imported granular fill, the use of dredged and excavated marine clay has become the preferred source of materials in reclamation activities. A common reclamation technique involves placing dredged clay lumps directly on top of other layers; these lumpy fills contain large initial inter-lump voids with the result that the fills experience substantial compression purely due to the closure of the void space. A practical solution therefore is to fill the void space with a granular soil to enhance the load-carrying capacity and to minimize the settlements of the reclaimed fills.;In this research a coordinated experimental investigation was undertaken to examine the consolidation behavior of composites fabricated using a number of spherical and disk-shaped clay inclusions placed within an artificial granular medium (ballotini). The results of this experimental research program indicated that the volume fraction, shape, configuration and the constitutive properties of both the clay inclusions and the granular component are all important factors that could affect the mechanical response of the soil composites. A computational scheme, validated using the results of the bench-scale experiments, was used to analyze the response of an idealized composite lumpy fill subjected to self-weight stresses, surcharge and a load applied through a rigid footing. The computational results indicated that the consolidation behavior of the composite lumpy layers can be significantly influenced by the volume proportion, location and configuration of the clay inclusions interspersed within the granular fill. The incorporation of the constitutive behaviors of the soil components, used in reclamation activities, into such a computational analysis could assist engineers in designing reclaimed fills where the least ultimate settlement occurs within the shortest time.