Abstract
This work reviews the transient two-phase flow in porous media with engineering applications in Geotechnics. It initially overviews constitutive relationships, conventional theories, and experiments. Then, corresponding limitations are discussed according to conflicting observations and multiphase interfacial dynamics. Based on those findings, the dynamic nonequilibrium effects were so defined, which could also be abbreviated as dynamic/transient effects. Four advanced theories have already been developed to resolve these effects. This review collects them and discusses their pros and cons. In addition, this work further reviews the state-of-art in terms of experimental methods, influential factors in dynamic/transient effects, and modelling performance, as well as micromodel and numerical methods at pore-scale. Last, the corresponding geotechnical applications are reviewed, discussing their applicability in effective stress, shear strength, and deformation. Finally, the entire review is briefed to identify research gaps in Geotechnics.
Highlights
Multiphase flow in porous media is a complex engineering problem
Theoretical, experimental, and numerical efforts on this application might deserve to be more investigated in the future. This comprehensive review is constructed for the transient two-phase flow in porous media and its engineering applications in Geotechnics
It commences from a literature review of conventional two-phase flow seepage in three sections: fundamental multiphase physics and soil water retention curve, steady-state and transient seepage theories with hydraulic properties, and experimental methods for relative hydraulic conductivity
Summary
Multiphase flow in porous media is a complex engineering problem. It covers various disciplines, including agriculture, hydrogeology, geotechnical engineering, petroleum engineering, biological engineering, and medical engineering. The theory of multiphase flow in porous media offers geotechnical engineers solutions to determine the hydro-mechanical behaviour of unsaturated soil under various environmental and hydraulic conditions [4] It can predict oil recovery efficiency during the gas/water injection process in deep reservoirs [3]. All reviews draw similar conclusions on the non-negligibility of dynamic nonequilibrium effects under transient flow conditions, the dependence of dynamic effects on fluid and porous media intrinsic properties, the importance of further experimental development, theoretical expansion, determination of constitutive parameters using inversion analysis, microscale physical and numerical modelling, etc. Based on the considerations mentioned above, this work aims to deliver a comprehensive and state-of-art review of transient two-phase flow in porous media under both instantaneous equilibrium and nonequilibrium conditions for any potential applications in Geotechnics. They did not recommend using the correction factor in the Fredlund and Xing [15] model because it lacks physical support for absolute zero water content at the suction of 106 kPa
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