Multiphase Flow in Porous Media: Dewatering and Consolidation
Date
2023
Authors
Huangfu, Zhihao
Editors
Advisors
Deng, An
Tian, Zhao Feng
Tian, Zhao Feng
Journal Title
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Thesis
Citation
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Abstract
Multiphase flow in porous media represents one of the most complicated processes that occur in a range of applications across science and engineering disciplines. The complexity escalates when the flows are driven under a negative pressure as often encountered in geotechnical engineering, petroleum exploration, and underground water resource cycling. The proposed study aims to model gas−liquid flows in porous media, calculate deformation of porous media induced by the two-phase flows, and capture pressure variation in vertical drains. This thesis comprises four article publications (Chapters 2 to 5) which are either published or submitted to journals for possible publication by the time of thesis lodgement. Chapter 1 is the Introduction. This chapter provides an overview of the research, highlights the research gaps, presents the research aims and objectives, and outlines the thesis structure. Chapter 2 comprises a paper “Large Strain Consolidation of Unsaturated Soil: Model Formulation and Numerical Analysis”. This paper has been published in the ACSE International Journal of Geomechanics. The content presents a novel numerical model to simulate the unsaturated soil consolidation utilising the Lagrangian–Convective coordinate system. The proposed model was solved via the explicit finite difference method and was verified against the conventional analytical solution. The developed model enabled the nonlinear soil properties including soil water characteristic curve, shrinkage curve, compressibility curve and permeability curve. A parametric study was conducted to focus on the effect of the initial soil degree of saturation on the consolidation degree. The results indicated that soil with a higher initial degree of saturation has a greater consolidation settlement, and vice versa. Chapter 3 presents the second paper manuscript, entitled “Vertical drain aided consolidation and solute transport”, which is under review by Computers and Geotechnics. This study coupled the consolidation model in Chapter 2 with the solute transport model and studied the dewatering and solute discharge efficiency under different consolidation conditions. The coupled equations were solved via the alternative direction finite difference time domain method. The model was experimentally verified and then applied to examine the effects of soil saturation conditions, solute transport conditions, and consolidation efforts on solute transport. The results showed that the dispersion process contributes to the solute discharge, whereas the contribution becomes less noticeable in unsaturated conditions. The solute sorption process counteracts the solute transport and delays the clean-up. The consolidation accelerates the transport of reactive chemicals but shows limited effects on the transport of non-reactive chemicals. Chapter 4 presents the third paper manuscript, entitled “Large strain consolidation model of vacuum and air-booster combined dewatering”. This manuscript was submitted to Computers and Geotechnics. The work presented a finite strain model for solving the vacuum and air-booster combined consolidation problem. The model also took account of soil desaturation due to air injection. The model was solved numerically via the alternative direction finite difference time domain method, and the solution was verified against the field test and laboratory measurement. Chapter 5 contains the fourth paper manuscript, entitled “Modelling air-water flow in the vacuum-aided vertical drain”, which was submitted to Geosynthetic International. This modelling work presented a numerical method used to estimate the vacuum-induced two-phase flow pressure distribution along the vertical drain. The soil medium was modelled as the orifice along the vertical drain. The proposed model was validated against the experiment and computational fluid dynamic results. A parametric study was conducted, and the results indicated that the nonlinear pressure distributions occurred in the drainpipe, and the pressure dropped more noticeably in the presence of air. The modelling suggests under one-atmosphere vacuum pressure, the drain lift depth is approximately 6.3 to 7.5m depending on the orifice size. Chapter 6 is the Summary of this thesis, concluding research contributions achieved and suggestions for further work.
School/Discipline
School of Architecture and Civil Engineering
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Architecture and Civil Engineering, 2023
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