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Soil Pores (soil + pore)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Dependence of the surface fractal dimension of soil pores on image resolution and magnification

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2003
A. Dathe
Summary Two recent investigations have reported contradictory trends concerning the effect of image resolution on the surface fractal dimension of soil pores, evaluated via image analysis. In one case, dealing with a preferential flow pathway and an ideal fractal, image resolution had no influence on the estimated fractal dimension, whereas in the other case, involving images of soil thin sections, the surface fractal dimension decreased significantly with image resolution. In the present paper, we try to determine the extent to which these conflicting observations may have been due to the different ways in which image resolution was varied. By narrowing down (up to 400 times) the field of view on progressively smaller portions of a textbook surface fractal, the von Koch island, one causes its apparent surface fractal dimension to decrease significantly. On the other hand, changing the resolution of images of soil thin sections (up to 6 times), while keeping the magnification constant, does not lead to appreciable changes in the surface fractal dimension. These results demonstrate that there is no real conflict in earlier reports, as long as both the resolution and the magnification of images are taken into account in image-based evaluations of surface fractal dimensions of soil pores. [source]

Applicability of the Washburn theory for determining the wetting angle of soils

HYDROLOGICAL PROCESSES, Issue 17 2007
Henryk Czachor
Abstract The Washburn theory is frequently applied to determine the wetting angle of soils. It is based on the porous medium being characterized as a set of cylindrical, straight capillaries. It is clear that this is an oversimplification as real soil pores vary at least as regards two important features: cross-section and tortuosity. In this study, a mathematical model of meniscus movement in a tortuous, sinusoidal shaped capillary was developed and the obtained analytical expressions for the wetting angle and for the pore radius were compared with the appropriate formula concerning the Washburn theory. The results demonstrate that the wetting angle of water in soil determined on the basis of the measured wetting front kinetics and of Washburn equations is likely to have an overestimated value due to the wavy, tortuous nature of inter-soil grain pores. The above conclusion was confirmed by capillary rise experiments. Wetting angles of methyl alcohol and of water measured on flat glass were 0 and 27·4° , respectively. Apparent wetting angles calculated from capillary rise in powdered glass kinetics and Washburn equation were 70 and 83° respectively. If the pore structure characteristics of porous media are not taken into account the applicability of the Washburn theory for soil wettability estimation seems to be very limited. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Groutability of cement-based grout with consideration of viscosity and filtration phenomenon

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 16 2009
Jong-Sun Kim
Abstract The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement-based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition, the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed-form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement-based grout in the soil matrix. The closed-form solution relevant to a particular spherical flow was modified by a step-wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot-scale chamber injection tests was performed to verify that the developed step-wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step-wise numerical calculation. Based on the filtration phenomenon, a viable approach for estimating the groutability of cement-based grout in a porous medium was also suggested, which might facilitate a new insight in the design of the grouting process. Copyright © 2009 John Wiley & Sons, Ltd. [source]