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Title: Numerical modelling of soft soils improved with stone columns
Author: Kamrat-Pietraszewska, Daniela
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2011
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Natural soft soils are very complex materials and geological processes greatly influence their stress-strain behaviour. Natural soft soils exhibit anisotropy and interparticle bonding, and their stress-strain response is time-dependent. Taking account of those soil characteristics is paramount for realistic and accurate predictions of soft soil behaviour. Geotechnical properties of natural soft soils can be improved with various techniques, such as stone columns. Stone columns are mainly used for settlement and consolidation time reduction, however underneath an embankment stone columns also enhance the slope stability. Despite the wide range of applications of stone columns, current design methods of stone columns are for the greater part based on simple assumptions and do not account for the complex soil-column interaction. Numerical methods are still fighting for their place in industrial design. They could be used, as a complementary solution to well-known empirical design proc edures, for gaining a better understanding of the behaviour of soil improved with stone columns and for the optimisation of existing design procedures. Behaviour of a stone column foundation is largely governed by the surrounding soil, its compressibility characteristics and the stress-strain-strength response. The models commonly used by civil engineering practitioners predict often inaccurate and over-conservative stress-strain response, as characteristics of soft soils are ignored and the complexity of the soil-column interaction is neglected. The novelty of this research lies in accounting for the complex features of natural soft soil behaviour, such as non-linearity, anisotropy, destructuration and viscosity, in soil modelling. Following that, the work enables optimisation of the design of stone column foundations by reducing the risk of unexpected ground movements. Three-dimensional numerical studies on the effect of mechanical and physical properties of stone columns and the impact of soft soil layer thickness are carried out by application of advanced constitutive models to represent the soft soil mass. Additionally, the research aimed for the development of an advanced constitutive model which takes account of all important characteristics of soft soil, leading to more realistic predictions of soft soil behaviour. Next, the influence of anisotropy, apparent interparticle bonding and viscosity on predicted stress-strain response of the stone column foundation constructed on soft soil was studied via a three-dimensional benchmark problem and the application of advanced constitutive models.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available