Influence Of Initial Water Content Research Articles

Collapse phenomena during wetting in granular media

We present an experimental study of identification and analysis of the collapse phenomenon in granular media, using a sample made of glass beads. The collapse potential of a soil depends on several parameters such as liquid limit, matric suction, dry apparent density, initial water content and the amount of small particles. In this study, we investigate the liquid effect during the wetting process, without external mechanical stress. Experimental tests at different initial water contents were made for different grain sizes. The equipment used is a triaxial device for unsaturated soils, instrumented with local axial and radial displacement sensors. The experimental results determined a critical water content of collapse, as well as the influence of initial water content, matric suction and grain size.

Influence of Initial Water Content on the Mechanical Behavior of Unsaturated Sandy Clay Soil

AbstractThe mechanical behavior of a sandy clay soil was investigated by a series of constant water content triaxial tests on unsaturated samples with suction measurements. The tests were carried out in double-cell triaxial cells on compacted samples and also on samples wetted and dried from the as-compacted conditions. A series of tests on saturated samples was also performed to provide a reference state for the unsaturated tests. Because the specimens were at high degrees of saturation (generally >80%), calculations based on effective stress showed a reasonable interpretation of the data for the critical state parameters M and λ. However, the intercept of the critical state line in the ν-axis (Γ) differed and increased with an increase in water content (at compaction). The data were also analyzed using the Bishop stress (p*) approach, and a better fitting was achieved in the stress plane, where it was possible to define a unique critical state line, where M was 0.91. However, in the ν-p* plane, differen...

Modified Liu-Carter Compression Model for Natural Clays with Various Initial Water Contents

The initial water content has a significant effect on the compression behaviour of reconstituted clays. This effect has to be considered in the Liu-Carter model to ensure the addition voids ratio only related to soil structure. A modified Liu-Carter compression model is proposed by introducing the empirical equations for reconstituted clays at different initial water contents into the Liu-Carter model. The proposed model is verified against the experimental results from the literature. The simulations by the proposed method are also compared with that by old method where the influence of initial water content is not considered. The results show that the predicted virgin compression curves of natural clays are similar, but the values ofbandΔeymay be very different.

Compression Behavior of Secondary Clay Minerals at High Initial Water Contents

This study shows the influence of initial water content on the compression behavior of secondary clay minerals: kaolin, illite, and montmorillonite. Oedometer tests were carried out on these minerals with different initial water contents which are ranging from one to two times their corresponding liquid limits. The findings show that the initial water contents can result in different compression behaviors of secondary clay minerals. The compression indices of secondary clay minerals, and , increase nonlinearly with increasing initial water contents, and compression behaviors among samples become insignificant gradually. Meanwhile, it is also noticed that the effect of initial water content on of montmorillonite is smaller than that of kaolin and illite. However, the effect of initial water contents on of secondary clay minerals is close. Due to the remolded yield stresses existing in remold soils, all the e∼logσ′ compression curves of the three secondary clay minerals present an inverse ‘S’ shape. The initial water contents have different effects on remolded yield stress of secondary clay minerals. It has most significant effect on illite, and less effect on kaolin and montmorillonite.

Experimental study of the air–steam mixture leakage rate through damaged and partially saturated concrete

This study is focused on the tightness of containment walls of nuclear power plants in case of loss of coolant accident. This kind of accident results in the rise from ambient conditions to a temperature of 140 °C and an air–steam mixture pressure of 5.2 bars. This rise creates high hydric, thermal and mechanical stress in concrete, impairing the tightness integrity of concrete wall. In this work, we propose to highlight experimentally the influence of initial water content of the sample, the compressive load and the percolating fluid on the hydraulic behavior of concrete. The tests are carried out on hollow cylindrical samples, using a device which allows to generate a gas mixture at the inlet and to measure the leakage rate at the outlet of the samples. As the tests are performed in isothermal conditions, the results show that at stress levels lower than 70–80 % of the peak stress, the leakage rate of the mixture is slightly influenced by both parameters (degree of saturation and stress). However, it can be noted that as the load exceeds this threshold value, the damage effect due to mechanical loading remains more important in the leakage rate evaluation.

Effect of feedstock water content and pyrolysis temperature on the structure and reactivity of spruce wood char produced in fixed bed pyrolysis

The influence of initial water content and temperature on the pyrolysis product distribution as well as on the structure and reactivity of the pyrolysis char was investigated. Spruce wood chips with 2.4%, 16.4%, and 55.4% initial water content were pyrolyzed in a tubular batch reactor at 500 and 800°C with a heating rate between 4 and 12.6°C/min. The structural features of the char samples were examined with scanning electron microscopy, Brunauer–Emmett–Teller (BET) method, and mercury porosimetry. The reactivity in CO2 was investigated using thermo-gravimetric analysis and a fixed bed quartz reactor.It could be seen that higher water content led to a higher yield of condensable products and a lower amount of char. At a pyrolysis temperature of 500°C the CO-content of the product gas did increase significantly with increasing water content. Moreover, initial water content had no significant effect on the microscopic structure of wood chars.The specific char surface area did increase with increasing initial water content up to the fiber saturation point. It was also observed that the specific char surface area was strongly influenced by the pyrolysis temperature. When the pyrolysis temperature increased from 500 to 800°C, the BET surface area became at least 200 times smaller and the average size of micropores became about 10 times smaller. Most likely, pyrolysis at 800°C induced more secondary reactions that were responsible for the occlusion of the micropores within the char [1].Finally, it was found that reactivity in CO2 significantly decreased with increasing pyrolysis temperature. However, initial wood water content did not have a significant effect on char reactivity in CO2.

Influence of Initial Water Content and Specimen Thickness on the SWCC of Fine-Grained Soils

Earlier researchers have demonstrated that the compaction effort and water content, type of soil and mineralogy, void ratio, fabric, and stress history influence the soil-water characteristics curve (SWCC) of fine-grained soils to a great extent. However, it should be noted that compacting the soil and retrieving specimens from the compacted mass for suction measurements is a tedious task. Also, many times, identical soil specimens with similar compaction states may result in varied pore-size distribution characteristics. Hence, for establishing the SWCC, soil specimens in the form of slurry of adequate consistency would be quite handy, particularly for maintaining uniformity in specimen preparation. With this in view, the current study was carried out to understand the influence of initial water content on the SWCC and to recommend its best suited value for conducting experiments. It has also been noted that suction measurement devices, such as pressure membrane extractor and the dew point potentiameter WP4, have limitations associated with the thickness of the specimen, which may become an important and deciding parameter. Hence, in this study, SWCCs were established for commercially available kaolin and bentonite clays by varying the initial water contents and thickness of their specimens. Details of the methodologies adopted for these investigations are presented in this paper. These investigations reveal that the initial water content influences only the initial portion of the SWCC for soil suction less than 500 kPa, while the specimen thickness does not significantly influence the shape of the SWCC. It has also been demonstrated that specimens prepared from the initial slurried state facilitate uniformity in suction measurements.

Influence of Heat Treatment on the Quality of Functional Gluten-Free Spaghetti

In this study the influence of initial water content and the extent of flour thermal pretreatment on both the dough rheological properties and the sensorial attributes of maize and chickpeas based gluten-free spaghetti were assessed. Results showed that samples with the highest initial water content had the highest values of elongation and shear viscosity, therefore dough with greater extensibility was obtained. Regarding the sensorial properties of non-cooked spaghetti, the overall quality of all samples had a very positive score with the exception of the samples with the highest initial water content and the lowest steam injection time that were scored just above the acceptability threshold because of their low resistance to break. The overall quality values of the cooked dry spaghetti were found to be around the acceptability threshold with the exception of the sample with the highest initial water content that showed a value higher than the threshold due to the highest values of bulkiness and adhesiveness.

Influence of Initial Water Content on the Wettability of Autoclaved Soils

Autoclaving is a commonly used practice to destroy microbial activity in soils but is thought to have a limited effect on other soil properties. Small changes in chemical composition have been reported, but there have been no previous reports of any alteration of physical properties. This study, however, showed that autoclaving can cause a major change in soil hydraulic properties. For samples with intermediate water contents (10–35% v/v), it caused severe or extreme water repellency in three of four soil types tested, although no effect for initially low or high water contents was found. These findings have important implications for any experimental work involving soil autoclaving as a pretreatment procedure but could also be used for generating otherwise similar samples differing only in terms of wettability.

Numerical analysis of water and solute transport in variably-saturated fractured clayey till

This study numerically investigates the influence of initial water content and rain intensities on the preferential migration of two fluorescent tracers, Acid Yellow 7 (AY7) and Sulforhodamine B (SB), through variably-saturated fractured clayey till. The simulations are based on the numerical model HydroGeoSphere, which solves 3D variably-saturated flow and solute transport in discretely-fractured porous media. Using detailed knowledge of the matrix, fracture, and biopore properties, the numerical model is calibrated and validated against experimental high-resolution tracer images/data collected under dry and wet soil conditions and for three different rain events. The model could reproduce reasonably well the observed preferential migration of AY7 and SB through the fractured till, although it did not capture the exact depth of migration and the negligible impact of the dead-end biopores in a near-saturated matrix. A sensitivity analysis suggests fast flow mechanisms and dynamic surface coating in the biopores, and the presence of a plough pan in the till.

Laboratory results from hydro-mechanical tests on a water unsaturated bentonite

Highly compacted bentonite has been proposed as the buffer material for embedding waste canisters in the Swedish concept for the disposal of nuclear waste. Although the bentonite is expected to become saturated in the repository, it is of importance to understand the process of saturation as it develops with increasing swelling pressure and decreasing suction. A laboratory programme has been carried out with the purpose to improve both the general understanding and the available models of the hydro-mechanical behaviour of unsaturated, swelling bentonite. The water saturation process is often modelled as driven by a gradient in suction (or negative pore water pressure). This study investigated the impact of factors such as void ratio, degree of saturation and external load on suction. The majority of the tests were designed to determine the increase in water content during free swelling or during constant volume conditions, where the swelling pressure derived by the prevented swelling has been measured. The water content was controlled by imposing a specified relative humidity for each test. Tests with constant water content and externally applied load were also performed. Relative humidity was measured in these tests. The clay used in the tests was MX-80, a commercial bentonite from American Colloid Co., with a liquid limit w L of about 500%. This paper illustrates the impact of confinement and influence of initial water content on the final swelling pressure and water content at an imposed relative humidity. Details of the testing techniques have also been given. In an associated paper a proposed hydro-mechanical model for the saturation process in bentonite, based on these results, has been presented [Dueck, A., Börgesson, L., 2007. Model suggested for an important part of the hydro-mechanical behaviour of a water unsaturated bentonite. Engineering Geology 92, 160–169].

Effect of high initial water content on cement-based sludge solidification

When solidifying/stabilising high water content materials, the water/cement (w/c) ratios are higher than those usually found in concrete engineering. However, an important question about the availability of the total measured water content can be asked. In this paper, the influence of initial water content on the mechanical behaviour of solidified dredged sludge is investigated. Water consumptions for three types of cement are measured after solidification with different w/c ratios. It has been observed that the three types of cement consume different quantities of water. The theoretical water consumption value expressed by unit mass of anhydrous cement is 0·42. Many observations concerning the water consumption compared with the replacement level suggest that the measured initial water is not totally available to hydrate the added cement. Lorsque l'on solidifie/stabilise des matériaux à forte teneur en eau, les rapports eau-ciment (w/c) sont plus élevés que ceux trouvé s habituellement dans l'ingé nierie du ciment. Cependant, on peut s'interroger sur la disponibilité de la teneur en eau totale mesuré e. Dans cet exposé, nous étudions l'influence de la teneur en eau initiale sur le comportement mécanique de la boue dragué e solidifié e. Nous avons mesuré les consommations en eau de trois types de ciment après solidification avec trois proportions w/c diffé rentes. Nous avons observé que les trois types de ciment consommaient diffé rentes quantité s d'eau. La valeur thé orique de la consommation en eau exprimé e par masse unitaire de ciment anhydre est de 0·42. De nombreuses observations concernant la consommation en eau comparé e avec le niveau de remplacement suggèrent que l'eau initiale mesuré e n'est pas totalement disponible pour hydrater le ciment ajouté

In vitro drug release mechanism and drug loading studies of cubic phase gels

Glyceryl monooleate/water cubic phase systems were investigated as drug delivery systems, using salicylic acid as a model drug. The liquid crystalline phases formed by the glyceryl monooleate (GMO)/water systems were characterized by polarizing microscopy. In vitro drug release studies were performed and the influences of initial water content, swelling and drug loading on the drug release properties were evaluated. Water uptake followed second-order swelling kinetics. In vitro release profiles showed Fickian diffusion control and were independent on the initial water content and drug loading, suggesting GMO cubic phase gels suitability for use as drug delivery system.

Changes in Clay Swelling and Shear Strength Properties with Different Sample Preparation Techniques

Abstract This paper presents the effect of compaction methods on soil swell pressure, unconfined compressive strength, and swell potential of three types of soils in Jordan. Undisturbed and disturbed soil samples were collected from the field and used for this study. Compacted soil specimens were prepared using dynamic compaction, static compaction, and kneading compaction. Swell potential test, swelling pressure test, and unconfined compression test were conducted on identical samples compacted by different methods, and having similar initial conditions to the undisturbed samples. Other sets of experiments were also conducted to examine the influence of initial water content on swell pressure and unconfined compressive strength under different compaction techniques. Results indicated that the undisturbed samples have the highest swelling pressure and swell potential values followed by dynamic compaction, while kneading compaction gave the lowest values for the three soils. For the same soil, it has been found that the swelling pressures of the undisturbed samples were 1.5, 1.96, and 3.07 times of that for the dynamic, static, and kneading compaction, respectively. Similar trends were obtained with regard to unconfined compressive strength and swell potential. The unconfined compressive strengths of the undisturbed samples were 1.35, 1.6, and 2.53 times higher than that of the soil specimen compacted according to the dynamic, static, and kneading procedures, respectively.

Measuring the water retention capacities (MRC) of different microcrystalline cellulose grades

The ability of various types of microcrystalline cellulose (MCC) to hold water when subjected to an applied force has been assessed by a centrifuge technique. By considering the final percent of water retained after a standard centrifugation, as a function of the initial water content, a moisture retention capacity (MRC) can be determined. Statistical analysis of the results identified that it was possible to divide the nine samples of MCC into six sub-sets in terms of final moisture content retained. Those types which contained added polymer had by far the highest water level remaining. In terms of the MRC value, statistical analysis again sub-divided the celluloses into six sub-sets, although different from those for the final water content. Again those types containing added polymer gave much higher MRC values. As experiments were carried out with initial water/MCC ratios of different levels, statistical analysis of the influence of initial water content on the MRC values was undertaken with each type of MCC. The results showed a varying dependence on initial water level with the different types of cellulose. To provide a value of MRC which characterised the cellulose, the maximum value of MRC at the lowest initial water level was identified. Samples of MCC with low values of MRC have been shown previously to require less water for processing by extrusion/spheronization, while celluloses with a high MRC value appear better for the limitation of water movement during the process of extrusion/spheronization. The water retention must, however, also be considered in association with the rheological properties of the wet powder mass. Thus, while the Avicel RC591 had the highest MRC value, its rheological properties are so that the production of pellets with such a type can be less effective than with other types of MCC.

The influence of soil structure and stress history on the soil–water characteristics of a compacted till

The soil–water characteristic defines the relationship between the soil suction and gravimetric water content, w, or the volumetric water content, θ, or the degree of saturation, S. Theoretical and empirical relationships are available to model the unsaturated soil properties such as the coefficient of permeability and shear strength using the soil–water characteristic and the conventional saturated soil properties. These procedures are attractive to engineering practitioners because rigorous laboratory tests on unsaturated soil are difficult and time-consuming and, therefore, costly. Various investigators generally have used the soil–water characteristic over a limited suction range (usually 0 to about 1500 kPa) to model the unsaturated soil behaviour. Soils, however, change from a saturated to a dry condition over a range of suctions from 0 to 1000 000 kPa. A rationale for extending the soil–water characteristic up to 1000 000 kPa is provided in this paper, and a method for estimating the residual state of saturation is presented. Soil–water characteristics were developed for the entire range of suctions from 0 to 1000 000 kPa on statically compacted clayey till specimens prepared at three different initial water contents. The influence of initial water content, soil structure and stress history, as it relates to the soil–water characteristic, has been studied and is reported in this paper. The initial water contents selected for this study represent the dry of optimum, optimum and wet of optimum conditions with corresponding densities determined from the standard AASHTO test. The results indicate that initial moulding water content has considerable influence on the resulting structure (and aggregation), which in turn influences the soil–water characteristics. In the low suction range (i.e. 0–1500 kPa), macrostructure governs the soil–water characteristics for specimens compacted with dry of optimum initial water contents and they exhibit a steeper slope. However, for the specimens compacted at wet of optimum, microstructure governs the soil–water characteristic behaviour. The soil–water characteristic of the specimens compacted at dry of optimum are influenced by the stress history; however, stress history appears to have no significant influence on the soil–water characteristics of the specimens compacted with wet of optimum conditions. The soil–water characteristic behaviour of specimens compacted with optimum initial water contents lies in between those of specimens compacted with water contents that are dry and wet of optimum. It appears that soil–water characteristics are not significantly influenced either by the soil structure (aggregation) or the stress history for the high suction ranges (i.e. 20 000–1 000 000 kPa).

Infiltration over Heterogenous Watershed: Influence of Rain Excess

Once the soil surface reaches saturation, rain excess is generated. This rain excess may run over and infiltrate in other areas of the watershed. In this study, we consider three scenarios of distributing rain excess/run-on to examine how it affects infiltration over a watershed. For these scenarios, we introduce simple solutions that allow the users to (1) estimate the ponded area-fraction of the watershed, and (2) determine the area-averaged infiltration. The solutions are practical because they require trivial computations. The solutions of ponding time and area-averaged infiltration account for the influence of initial water content and contain parameters with precise physical meaning. We find that area-averaged infiltration depends strongly on the distribution of rain excess at the surface. Thus we question the use of many stochastic area-averaged infiltration models that ignore the influence of rain excess.

Influence of initial water content and soaking on compressibility and shear strength of decomposed granite soil : Onitsuka, K; Yoshitake, S Proc Symposium on Environmental Geotechnics and Problematic Soils and Rocks, Bangkok, December 1985P545–553. Publ Rotterdam: A A Balkema, 1988

Influence of initial water content and soaking on compressibility and shear strength of decomposed granite soil : Onitsuka, K; Yoshitake, S Proc Symposium on Environmental Geotechnics and Problematic Soils and Rocks, Bangkok, December 1985P545–553. Publ Rotterdam: A A Balkema, 1988