Plots Of Water Content Research Articles

Quantification of desiccation cracks using X-ray tomography for tracing shrinkage path of compacted expansive soil

Compacted expansive soils undergo large volumetric changes during wet–dry cycles owing to the seasonal moisture fluctuations, and during drying the shrinkage is accompanied with the desiccation cracks. This paper presents the shrinkage behaviour of compacted expansive soil specimen, under a vertical stress of 12.5 kPa, in terms of void ratio–water content plot during second drying cycle. Accurate characterization of shrinkage behaviour along with the soil–water characteristic curve in terms of degree of saturation versus water content helps in the development of constitutive relation such as void ratio–suction relationship, which is vital for the prediction of unsaturated soil properties. However, the expansive soils develop large desiccation cracks during drying, which hinder the accurate volume measurement of desiccated soil specimen using vernier caliper as the vernier caliper measurements do not capture the volume of cracks developed within the soil specimen. The mercury displacement method and fluid displacement methods measure the volume of the soil specimens accurately, but the methods are either destructive or hazardous, and consequently, the continuous measurements are not possible. In order to overcome these limitations, the XCT imaging experiments were carried out along with the image analysis technique using ImageJ software and vernier caliper height measurements for tracing the volume change during the second drying path. The exact volume change during and at the end of drying process was estimated by deducting the cracks volume from the volume of specimen arrived from the vernier caliper measurements. Also the volume change at the end of drying process was measured using both XCT imaging experiments and mercury displacement method, and the results were compared. The cracks volume was used for defining the void ratios pertaining to specific components like cracks void ratio, annular gap void ratio, discontinuities void ratio (annular gap + cracks), soil pores void ratio and total void ratio (including and excluding the annular gap). The experimental results in terms of void ratio pertaining to various components, during drying process, were presented in terms of void ratio–water content plots and compared with the void ratio–water content plot of specimen reconstituted from slurry. The void ratio–matric suction constitutive relationship was developed from the void ratio–water content plot and soil–water characteristic curve.

New Analytical Solutions to 2-D Water Infiltration and Imbibition into Unsaturated Soils for Various Boundary and Initial Conditions

Fluid infiltration and imbibition into unsaturated soil are of vital significance from many perspectives. Mathematically, such transient flows are described by Richards’ equation, a nonlinear parabolic partial differential equation with limited analytical solutions in the literature. However, the choice of exponential model for water content and hydraulic conductivity linearizes the nonlinear Richards’ equation, making it possible to obtain an analytical solution via classical approaches. In this study, separation of variables and Fourier series expansion techniques are used to derive new analytical solutions to 2-D vertical and horizontal infiltration and imbibition into unsaturated soils for nonsymmetrical boundary and nonuniform initial conditions. A total of 11 cases are considered, where high water content is imposed on the top, side, or bottom edges of the sample and water is infiltrated (from the top and/or side boundaries) and imbibed (from the bottom boundary) into the sample. Residual water content and/or no-flow boundary condition are assumed on other edges of the sample. Initial conditions include 7 cases of constant residual water content, 2 cases of sinusoidal, and 2 cases of exponential water content functions over the sample. Presented analytical solutions are such that both steady and unsteady solutions may be obtained from a single closed-form solution. Two-dimensional and 3-D plots of water content are presented for the transient as well as steady-state conditions. To illustrate the use of the derived equations, water content values from numerical solutions are compared to those from analytical solutions for four cases, showing a maximum error of <2 %. The presented analytical solutions may be used as a benchmark for verification and accuracy assessment of numerical approaches where nonsymmetrical boundary and/or nonuniform initial conditions exist.

Using the Continuously Disturbed Line to Estimate the Mechanical Behaviour of Unsaturated Compacted Soils

A simple technique which approximates the continuously disturbed line (CDL) using the relationship between water content and matric suction of compacted fine-grained soils, or apparent continuously disturbed line (CDLa) is presented. The CDL is defined as the relationship between a soils water content and suction reached by a soil specimen sheared under constant water content conditions (Croney and Coleman, in J Soil Sci 5(1):75–84, 1954). The critical state line (CSL), generated from specimens sheared under constant net normal stress, and the approximate continuously disturbed line (CDLa) appear to overlap at higher suction values. From plots of water content against matric suction, the CSL appears as a bi-linear relationship which lies below the CDLa with a shallower slope at lower matric suctions. The intersection point of the CSL and CDLa corresponds to the point where a unique value of the microstructural water content, e wm , can be back-calculated from the shear strength data. The relationship between the void ratio and the water content of compacted specimens provides an indication of the moisture content when the air entry value is reached.

Unified Analysis of Dewatering and Drying of Sludge Cake

To remove water from a suspension one needs to break down the binding energy between the adjacent water and the solid surface and to convey this water out of the suspension system. Using the binding energy between water and solids and the disrupting energy provided by mechanical and thermal means, this work presents a unified analysis on the dewatering of wet materials using binding energy as a clarification index. The binding energy versus residual water content plot for a wastewater sludge estimated the extent of dewatering each stage and the corresponding energy requirement.

Effects of metal–counterion interactions on the percolation in microemulsions composed of bis(N-octylethylenediamine)metal(II) complexes in water/benzene and water/chloroform systems

Self-diffusions and electric conductivities of microemulsions composed of surfactant metal complexes, dianionobis(N-octylethylenediamine)zinc(II) (aniono=chloro or nitrato), dichlorobis(N-octylethylenediamine)cadmium(II), and bis(N-octylethylenediamine) palladium(II) chloride (=ZnCl2(oct-en)2, Zn(NO3)2(oct-en)2, CdCl2(oct-en)2, and [Pd(oct-en)2]Cl2, respectively) were studied in water/benzene or water/chloroform mixed solvent system. The electric conductivities of the solutions increase in the order, CdCl2(oct-en)2<ZnCl2(oct-en)2<Zn(NO3)2(oct-en)2≪[Pd(oct-en)2]Cl2 systems. The profiles of the plots of the diffusion coefficients and of the electric conductivities versus water content depend on the ionicity of the metal-anion bond, i.e. in the [Pd(oct-en)2]Cl2 and Zn(NO3)2(oct-en)2 systems both the diffusion coefficients and the electric conductivities are positively dependent while for the other two systems the slopes of the plots are negative. Among them, it is characteristic that the electric conductivity versus water content plot for the palladium complex system shows a sharp peak at W0 (=[water]/[Pd complex])=43. These properties were explained on the basis of the pre-percolation phenomenon.

Deep-reaching liquefaction potential of marine slope sediments as a prerequisite for gravity mass flows? (Results from the DSDP)

Plots of water content ( w) and Atterberg liquid limits ( w L) versus depth, coupled with measurements from young submarine mass flows, support the concept that many fine-grained, but low-cohesive slope sediments are susceptible to liquefaction and can, as a result of dynamic loading (earthquakes and storm waves), be transformed into mud flows without the uptake of additional water. The in-situ water content w can be higher or approximately equal to w L (boundary between the plastic and liquid state of a soil) usually in the uppermost few meters, but frequently also tens or even some hundreds of meters below the sea floor. Such a substantial liquefaction potential is particularly common in sediments rich in silt-size biogenic particles and in regions of high sedimentation rates, causing underconsolidation. It is not clear whether changes in the salt concentration and chemistry of interstitial water versus depth in core exert some influence on w L and the liquefaction potential. The average “field liquid limit” of the total mass flow can be even lower than w L of small, only fine-grained homogenized samples, if part of the dislocated material is carried unchanged as lumps of mud by a liquefied matrix. w and w L often decrease in a similar way versus depth in sediments rich in microfossils due to the onset of slight chemical diagenesis with increasing burial depth. Thus, in spite of increasing compaction, a high liquefaction potential may be maintained, until finally substantial lithification reduces w to values lower than the plastic limit, w p, and completely alters all the mass physical properties.

Electrical impedance changes and water content in O/W emulsions during evaporation

Synopsis A method for measuring the variation of electrical impedance (Z) of thin layers (0.1 mm) of O/W emulsions during evaporation in a controlled environment is presented. The evaporation of an emulsion base (A) either as such and containing 1% glycerin (B) or 1% sodium pyrrolidonecarboxylate (C) was investigated for 120 min at constant air temperature (25 degrees C) and relative humidity (55%). The measured impedance of the emulsion layers increased by three orders of magnitude during the evaporation cycles. The relationship between impedance and water content of the evaporating emulsion layers was investigated. Each emulsion showed a complex linear relationship between log Z and water content, the relationship being represented by two (three, for emulsion A) linear portions in the graph. Plots of water content vs. time, temperature vs. time and rate of water loss vs. water content of the emulsion layers are presented. The data appear to indicate that evaporation proceeds via distinct stages, whose correspondence to different mechanisms of water evaporation is discussed. The potentiality of the present method for water analysis, and for investigating structural changes in emulsions during evaporation, is also discussed.

Dielectric properties of water of adsorption on protein crystals

AbstractThe dielectric properties of dry and wet protein crystals were studied in a wide frequency range. The dry protein crystals did not have appreciable dielectric constant until the water content was about 15–20%. However, further increase of water of hydration (and/or adsorption) suddenly increased the dielectric constant of the crystals, and it reached a very large value which cannot be explained merely by the orientation of water of hydration (and/or adsorption). However the increase of dielectric constant leveled off rapidly, and further addition of water did not have significant effect. Thus the dielectric constant–water content plot followed a curve which was similar to the Langmuir adsorption isotherm. This fact strongly indicates that the dielectric constant of hydrated crystals arises, for the most part, from the polarizability of the first hydration layer of the protein molecules, which supposedly have an icelike structure.