E-Thesis 259 views
Improving Deep Foundation Construction by Simulation Approaches: CFD and CFD-DEM / SHUAI SHU
Swansea University Author: SHUAI SHU
DOI (Published version): 10.23889/SUThesis.69348
Abstract
Deep foundations, such as piles and diaphragm walls, are increasingly being applied in modern high-rise or high-strength-required buildings. Based on the cooperation with EFFC/DFI Task Group, we participated in their field research study, which includes 20 site visits and experimental studies in Euro...
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Swansea University, Wales, UK
2025
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Li, C., and Thomas, H. R. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa69348 |
| Abstract: |
Deep foundations, such as piles and diaphragm walls, are increasingly being applied in modern high-rise or high-strength-required buildings. Based on the cooperation with EFFC/DFI Task Group, we participated in their field research study, which includes 20 site visits and experimental studies in Europe and US. With numbers of data acquired and two times site visits and works involved, we got the understanding of how deep foundations are constructed, what topics that industries are concerning about, and what can be concluded from the systematic experiments. Importantly, we have also identified challenges that cannot be addressed through site tests or traditional experiments, while can be effectively resolved using numerical simulations. Concrete is the most widely used building material in modern construction, consisting of at least four components: water, cement, fine aggregate (sand) and coarse aggregate (gravels).With the addition of superplasticizer, concrete adopts more fluid properties and is referred to as Self-Compacting Concrete (SCC). The SCC does not need any extra compaction and is able to compact itself by flowing with its own weight. In numerical simulations, SCC is often regarded as pure Bingham fluid. However, most part of fresh concrete is actually solid, and regarding it as pure fluid cannot study segregation, bleeding, passing through rebars and some more defects. Therefore, regarding SCC as a combination of fluid (mortar) and particles (gravels) makes more sense. Hence, in this thesis, both modelling schemes of SCC, pure fluid modelling and fluid-particle coupling modelling, are employed. Computational Fluid Dynamics (CFD) is powerful and well-established technique to simulate fluid flow. Discrete Element Method (DEM) is a common method used to solve particle interactions. However, although CFD-DEM coupling has rapidly developed in the recent decade, a lot of issues still need to be studied. In this study, the interaction forces between the particles and between fluid and particle are systematically reviewed, which includes contact forces between particles (normal, tangential and rolling forces), non-contact forces between particles (the van der Waals force, electrostatic force and capillary force) and fluid-particle interaction forces (buoyancy force, drag force, lift force, virtual mass force and Basset force). The most suitable model of each force is selected to be employed in the CFD-DEM simulation according to the literature statement, yet some forces like non-contact forces between particles are ignored in our concrete simulation due to inadaptability. Based on these involved interaction forces and CFD, DEM theories, an in-house code was written by C++to achieve CFD-DEM coupling simulation. The in-house code was initially developed by senior members in the research team and then improved by myself in some aspects including the comprehensive interaction forces implementation as previously introduced, and some corrections regarding volume fraction mapping between the CFD and DEM solvers. With these works done, the calculation accuracy of the in-house code is massively improved, which makes it possible to run some simulations to achieve decent parametric study or experiment validation. At the end of the study, two scales of simulation, the smaller-scales concrete workability tests and larger-scale pile concreting procedures, were conducted. For the concrete workability tests simulation, three tests, slump flow test, V-funnel test and L-box test, were included, and both CFD simulation and CFD-DEM simulations were implemented to compare with the lab experimental result. A methodology to obtain the rheological parameters of concrete/mortar from workability test results were developed so that it is possible to duplicate experiments by numerical simulations with a well-designed process. For the pile concreting simulation, a feasibility study is introduced since the dimension of the pile can vary in a quite large range and many different types of simulation can be implemented according to the industries’ concerns. Hence, a 8 m long pile was modelled as a benchmark to demonstrate the simulation pattern so that different dimensions of pile element can be modelled and simulated as well. Unfortunately, in this framework, only CFD scheme was employed to simulate due to the super high computational power needed for CFD-DEM simulations. However, it is still valuable to establish this benchmark and CFD-DEM simulation is hopefully to be achievable when the computational method and computer hardware are further developed in the future. |
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| Item Description: |
A selection of content is redacted or is partially redacted from this thesis to protect sensitive and personal information |
| Keywords: |
Computational Engineering, Deep Foundation, Computational Fluid Dynamics, Discrete Element Method, Self-Compacted Concrete |
| College: |
Faculty of Science and Engineering |
| Funders: |
CSC |