Shukla, Palak;
(2019)
Modelling of a stone column-clay composite system using the discrete element method.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Stone columns have been studied extensively over the last 40 years via experimental and finite element models. The use of the discrete element method (DEM) to investigate the particle level behaviour of a stone column is relatively unexplored, and the few studies that have been carried out use a coupled modelling technique. Investigating the behaviour of a stone column using DEM could be utilised to test and suggest improvements to stone column design. The first part of this study presents a new DEM model for clay; it takes into account the structure of a clay soil, where clay platelets and adsorbed and free water are modelled using clump and balls respectively. Volume changes due to pore water changes are modelled for the first time through an algorithm that changes the free water particles sizes depending on the load of the model, i.e. they reduce their size when loaded above a threshold and increase upon unloading. The method employed to model pore water dissipation can then also be used for the same purpose in a DEM model of granular soil. The new clay model enables DEM to be used to model problems where the behaviour of clay and its interaction with the surroundings is important. The model was validated against oedometer test data with a view to replicate reasonably the compression and swelling indices of clay. A good agreement was found between the DEM and the experiments. The second part of this study uses the clay DEM model to investigate the stone columnclay composite system. Three column lengths and a single column diameter are modelled; clumps are used to model the column material and the material properties determined via biaxial tests. Experiments were again used to validate the behaviour of the composite system. Finally, using the validated column-clay interaction, three new column geometries have been proposed and tested, showing that increasing the diameter of a column along the critical length, such that the column has a partial conical shape results in nearly doubling the load-carrying capacity of the column. This initial study opens the doors to the development of new installation techniques that will increase the scope of use of stone columns, possibly enabling them to be considered as foundation systems and not only for ground improvement.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Modelling of a stone column-clay composite system using the discrete element method |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10085985 |
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