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Vulnerability of earth material to water: A state of the art
Published in Paulo J.S. Cruz, Structures and Architecture: Bridging the Gap and Crossing Borders, 2019
E. Pauporté, L. Sgambi Université Catholique
First, in an unsaturated granular medium, it is the capillary bridges created by the liquid phase between the solid grains that determine the degree of cohesion. Thus, between the plastic soil used to shape an adobe brick and the water-equilibrium brick, or dry brick, the proportion of water decreases from +/-25 % to +/-2% (Moevus et al., 2013) and the compressive strength, initially practically zero, can reach up to +/-2,5 MPa (Kouakou and Morel, 2009). Excess water causes the capillary bridges to fuse and reduces the cohesion of the material, just as the total absence of water causes the capillary bridges to disappear and thus disintegrate the soil. The aim is therefore to determine an optimum water content. Moreover, between a pile of loose earth and the same earth freshly rammed into a mud wall, the water level does not vary, but the cohesion of the earth is radically different. The reorganization caused by the ramming, by increasing the compactness and coordination of the earth, multiplies the capillary bridges and thus its cohesion.
Mechanical behavior of road materials
Published in Bernardo Caicedo, Geotechnics of Roads: Fundamentals, 2018
Two stages of capillarity between spherical particles can be distinguished, as shown in Figure 5.12: At low levels of saturation, water is in its pendular regime, and capillary bridges are created between particles. These bridges generate intergranular forces located at the contact points between particles and whose directions are orthogonal to the tangent planes, see Figure 5.12a.At high levels of saturation, air is in the form of isolated bubbles and does not contribute to the strength of any arrangement of particles but does affect compressibility (i.e. funicular regime), see Figure 5.12b. For this range of saturation, Terzaghi’s concept of effective stress remains valid.
Measuring stiffness of soils in situ
Published in Fusao Oka, Akira Murakami, Ryosuke Uzuoka, Sayuri Kimoto, Computer Methods and Recent Advances in Geomechanics, 2014
Fusao Oka, Akira Murakami, Ryosuke Uzuoka, Sayuri Kimoto
ABSTRACT: The micro-mechanism of the capillary strengthening effect is studied in this paper with the aid of Discrete Element Methods (DEM) and the Stress-Force-Fabric (SFF) relationship. For an unsaturated granular material in pendular regime, pore water is discontinuously distributed at contact points in the form of capillary bridges, leading to the capillary force being the sum of the force component induced by air-water pressure difference on the section of the bridge neck and the force component induced by surface tension. Such a formulated contact model has been implemented in the DEM simulations. Directional statistical theory has been applied to study the statistical features of the contact interactions, the water bridges and the capillary forces. The impact of water bridges on the strength of unsaturated granular material has been interpreted through the SFF relationship to explain the capillary strengthening effect. Specimens with more uniform water distributions were found of higher shear strength, suggesting the impact for water distributions, a topic for more research.
A review of moisture migration in bulk material
Published in Particulate Science and Technology, 2020
Jian Chen, Kenneth Williams, Wei Chen, Jiahe Shen, Fangping Ye
However, Equation (13) can only be used to calculate the force between two particles. For the liquid bridge force and energy among three particles, some researchers gave the equations in different circumstances including pendular, funicular and capillary bridges, but they did not consider the effect of gravity, either (Urso, Lawrence, and Adams 1999). Murase, Mochida, and Sugama (2004) explored the retention ability and the shape of the liquid bridge between two spheres and among three spheres. They also researched the dynamic tensile strength when the upper sphere was moving upward at the speed of 0.2 m/s and 2.0 m/s, and concluded that it was much larger than static tensile strength. In other research, they gave the dimensionless form of their experimental results about the tensile strength when the upper sphere was moving upward (Murase et al. 2008).
Compact aerosol aggregate model (CA2M): A fast tool to estimate the aerosol properties of fractal-like aggregates
Published in Aerosol Science and Technology, 2023
Cyprien Jourdain, Jonathan P. R. Symonds, Adam M. Boies
Upon aggregation, agglomerates originally in point contact coalesce to create chemically-bonded (sintered) aggregates, resulting in a change of particle transport, radiative, and electron transfer properties (Eggersdorfer et al. 2012). The aggregates morphology evolves following the extent of the sintering process, from the formation of necks between primary particles to a spherically-shaped particle. By analogy with the excess free energy responsible for the gas-liquid phase transition in the vicinity of negatively curved surfaces building capillary bridges (Orr, Scriven, and Rivas 1975; Crouzet and Marlow 1995), a gradient of stress (solid phase) results in material diffusion toward the necks.
Theoretical and experimental study of capillary bridges between two parallel planes
Published in European Journal of Environmental and Civil Engineering, 2022
Hien Nho Gia Nguyen, Olivier Millet, Chao-Fa Zhao, Gérard Gagneux
A capillary bridge is created when a small volume of water is injected between two adjacent solids due to the surface tension of liquid. Capillarity is responsible for a wide range of natural phenomena and engineering processes (Duriez & Wan, 2017; Hicher & Chang, 2007; Nguyen, Zhao, Millet, & Gagneux, 2019d; Scholtès, Chareyre, Nicot, & Darve, 2009; Soulié, Cherblanc, El Youssoufi, & Saix, 2006; Zhao, 2017; Zhao, Kruyt, & Millet, 2019), such as water movement in soils, sand castle, fertiliser storage and handling, adhesion of small particles to solid surfaces, attraction between hydrated hydrophilic surfaces. It is therefore valuable to study the capillarity at the micro scale: liquid bridging between spherical particles and planar surfaces. This problem has received high attention for a long time by using theoretical and experimental approaches, based on a consistent theory proposed by Young and Laplace in the early nineteenth century (Delaunay, 1841; Fisher, 1926; Gagneux, Millet, Mielniczuk, & El Youssoufi, 2017; Gagneux & Millet, 2014; Zhao, Kruyt, & Millet, 2018; Zhao, Kruyt, et al., 2019, Zhao, Kruyt, & Millet, 2020). Analytical studies of the meridional profile of liquid bridges of revolution are originated from the pioneering work of (Delaunay, 1841) which considers surfaces of revolution of constant mean curvature. Based on this consideration, the meridional profile of capillary bridge may be a portion of nodoid, unduloid or some limit cases (catenoid, cylinder or torus). In particular, (Plateau, 1864) has succeeded in classifying surfaces of liquid bridge between two solids into a sequence known as ‘Plateau’s sequence’. Besides, (Erle, Dyson, & Morrow, 1971; Gagneux & Millet, 2014; Kruyt & Millet, 2017; Lian, Thornton, & Adams, 1993; Zhao et al., 2018; Zhao, Kruyt, et al., 2019, Zhao et al., 2020) have investigated the capillary bridge between two spherical particles; (Orr, Scriven, & Rivas, 1975; Rubinstein & Fel, 2014) concentrated on the classification of the meniscus shape of the liquid bridge between a sphere and a plane for imposed capillary pressure; (Reyssat, 2015) has studied experimentally and theoretically capillary bridges between a plane and a cylinder. Relating to the capillary bridge connecting two planar surfaces, some relevant analytical studies on the stability of capillary brige have been presented in Dejam, Hassanzadeh, and Chen (2015), Vogel (1987), and Vogel (1989). These mentioned studies of capillary bridges between parallel plates are limited to the case of identical material of the surfaces, where the contact angles stay the same, yielding symmetrical liquid bridges (see for instance Fortes, 1982). From the solution of Young-Laplace equation, several useful properties of the capillary bridge can be obtained, such as surface area, volume of liquid and capillary force (Kralchevsky & Nagayama, 2001).