Highly heterogeneous and anisotropic conditions in rock comprising double porosity and complex geometries of defects affect stability, stress conditions, groundwater vulnerability and recharge, drainage and dewatering practices, corrosivity, and integrity of infrastructure, to name a few examples. Movement of water at partial and highly variable saturation is very complex, depending on very smallscale variations (e.g. orientation, aperture, roughness, bridging, infill) in ground conditions as well as very subtle changes in moisture content (e.g. wetting vs drying). In contributing to this, a number of physical experiments were conducted in the laboratory or mimicked in the field. Experiments progressively assessed the influence of parameters, including assessment of the cubic law under smooth parallel plate models, fracture intersection, geometrical variation and verification with natural rocks at highly variable hydraulic head conditions. Some were subjected to differing gravitational accelerations to scale the vertical dimension. Studies contribute to flow regimes (laminar, turbulent, rotational, irrotational), mechanisms (droplets, rivulets, films, etc.) and scenarios (capillary barriered vs basally confined perched systems, etc.) of variably saturated rocks, as well as the interface between soil and rock. Where possible, a link is established between available theoretical understanding and empirical approaches to physical experiments and field verification experiments. Here, hydraulic parameters are estimated to improve the quantification of said parameters at discrete scale rather than assuming single values for bulk systems with the hope of eventually upscaling the models to larger representative elementary volumes, or to infer the behaviour under differing pressure conditions such as for pressure tests. Behaviour is inferred for fractures of changing orientation, changes in medium from soil to rock, and for alternation between wetting and drying of different media. Selected experiments are presented to highlight novel findings and the way forward. The incorporation of behaviour under variable saturation contributes to fundamental rock mechanics theory.

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