- Title
- Adaptive discontinuity layout optimisation for geotechnical stability analysis
- Creator
- Crumpton, Mason
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Discontinuity Layout Optimisation (DLO) is a novel geotechnical stability analysis method which is based on the upper bound limit theorem. In principal, the method works by identifying an optimum collapse mechanism in a mesh of many potential mechanisms which are constructed by drawing velocity discontinuities between pairs of nodes in a grid. This approach leads to a simple formulation and avoids the numerical complications associated with modelling complete load-displacement relationships. It also has a low dependence on a priori information as meshes do not explicitly employ rigid blocks or finite elements which perform best when orientated according to the stress or velocity field at failure. However, the DLO method leads to large optimisation problems which are impractical to solve without smart algorithms. Since DLO was pioneered by Smith & Gilbert in 2007 [1], it’s functionality has been extended to model a wide range of geotechnical processes and phenomena, but there have been few developments published that concern its efficiency. This thesis describes a range of new developments for enhancing the performance of the DLO method. These include modifications to the iterative optimisation procedure at its core, and a new Adaptive Discontinuity Layout Optimisation (ADLO) procedure. The ADLO procedure improves performance by using a posteriori interpolation error estimates to refine meshes so that fewer nodes are needed to attain a specific degree of solution accuracy. Ultimately, all the new developments seek to improve performance by reducing the DLO optimisation problem size, or number of iterations needed to solve it. The new developments have been incorporated in an enhanced DLO algorithm and an adaptive DLO algorithm which were implemented in a Layout Optimisation Analysis Software (LOAS) package. This software was used to analyse a series of geotechnical stability problems so that the performance of the algorithms could be studied and compared with the Finite Element Limit Analysis (FELA) method ([2],[3],[4],[5]). It was found that all but one of the new developments consistently improved the performance of the DLO method by reducing the analysis time and optimisation problem size needed to attain a specific degree of solution accuracy. When the enhanced DLO, adaptive DLO, and FELA analysis methods were compared it was found that, for the stability cases considered, the DLO based methods were competitive with FELA in terms of computational performance.
- Subject
- geotechnical stability analysis; limit analysis; discontinuity layout optimisation; adaptive meshing
- Identifier
- http://hdl.handle.net/1959.13/1390955
- Identifier
- uon:33147
- Rights
- Copyright 2018 Mason Crumpton
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 4 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 235 KB | Adobe Acrobat PDF | View Details Download |