Limited Water Content Research Articles

Effect of initial water content and pore water chemistry on intrinsic compression behavior

ABSTRACTThe effect of initial water content (w0) and pore water chemistry on the intrinsic compression curve of clays was investigated experimentally. The test results indicate that w0 had a considerable effect on the intrinsic compression curve of a clay, and the degree of the effect is a function of pore water chemistry. The fundamental mechanism of the effect of w0 and pore water chemistry on the intrinsic compression curve is through its influence on the microstructure of clays. For relatively stable flocculated microstructures, the effect of w0 will disappear under a small value of effective vertical consolidation stress, σ′v, for example, σ′v < 20 kPa; under one-dimensional deformation condition, but for a dispersive microstructure, the effect of w0 can remain up to σ′v > 1,000 kPa. Furthermore, it has been shown that when σ′v is larger than the remolded yield stress, almost all the test data follow the intrinsic compression line (ICL) proposed by Burland. Finally, based on the test data, a new equation for estimating void ratio () under σ′v = 100 kPa on ICL from the void ratio (el) corresponding to the liquid limit water content has been proposed.

Factors influencing undrained strength of fine-grained soils at high water contents

ABSTRACTUnderstanding the undrained strength of fine-grained soils has been of interest to geotechnical researchers from many practical considerations. In several civil engineering applications, water content of soil is quite high being near or above the liquid limit of soils, and understanding the factors responsible for imparting the strength of soil at high water contents is of great significance. Recently, it has been reported in the literature that the shear strength of soils at these limiting water contents has significant variation. However, the reasons and the factors that probably influence for this variation have not been reported in the literature. This experimental investigation is an attempt in the direction of understanding the reasons for the variation in the undrained strength at higher limiting water content, namely liquid limit considering the various influencing factors like clay mineralogy and fine-sand content present in soil used for determining liquid limit. The results from this study are quite revealing and have been explained based on the mechanisms controlling the undrained strength at liquid limit.

Soil degassing at the Los Humeros geothermal field (Mexico)

The Los Humeros geothermal field is the third most important producer of geothermal electricity (70MW) in Mexico. Geothermal fluids are hosted in fractured andesitic lavas and mostly consist of high enthalpy steam with limited water content (vapor fraction>0.9). Despite the high reservoir temperature (~300–400°C), thermal manifestations at the surface are scarce and locally appear as steaming grounds, weak steam vents and advanced argillic alteration. Geothermal fluid upflow from the reservoir towards the surface is limited by welded ignimbrite deposits that act as a low-permeability barrier. In this study, we present the first measurements of CO2, CH4 and H2S degassing rates from the soil performed at Los Humeros. Flux measurements were complemented with δ13C composition of degassing CO2 and soil temperatures to discuss gas origin and thermal anomalies. We measured high soil degassing rates (up to 7530gm−2d−1 CO2, 33gm−2d−1 CH4 and 22gm−2d−1 H2S) in three localized areas (Humeros North – HN, Humeros South – HS and Xalapazco – XA) as well as high soil temperatures reaching the boiling temperature at the local altitude (90.6°C). The particular location of these three areas suggests that the steam-dominated reservoir degases to the surface through permeable faults crossing the ignimbritic deposits. The remaining surveyed areas are characterized by weak CO2 fluxes (≤44gm−2d−1), non-detectable CH4 and H2S fluxes, and lower soil temperatures (5–21°C). The compositions in δ13CCO2 from HN-HS-XA areas (δ13CCO2=−7.94 to −2.73‰) reflect a magmatic source with some possible contribution from the sedimentary basement, as well as fractionation induced by boiling and CO2 dissolution in shallow water bodies. We also discuss the processes causing the spread in CO2/CH4 flux ratios. Finally, we estimate the heat output from the three high degassing areas to a value of 16.4MWt.

Assessment of clay stiffness and strength parameters using index properties

A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is assessed using the site-specific variation of the natural water content with the effective mean stress. Subsequently, an iterative process is envisaged to obtain the clay stiffness and strength parameters. The at-rest earth pressure coefficient, as well as bearing capacity factor and rigidity index related to the cone penetration test, is also acquired from the analyses. Comparisons are presented between the measured clay parameters and the results of corresponding analyses in five different case studies. It is demonstrated that the presented approach can provide acceptable estimates of saturated clay stiffness and strength parameters. One of the main privileges of the presented methodology is the site-specific procedure developed based on the relationships between clay strength and stiffness parameters, rather than adopting direct correlations. Despite of the utilized iterative processes, the presented approach can be easily implemented using a simple spreadsheet, benefiting both geotechnical researchers and practitioners.

High-Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under Ambient Conditions.

Mesocrystals of high-magnesian calcites are commonly found in biogenic calcites. Under ambient conditions, it remains challenging to prepare mesocrystals of high-magnesian calcite in aqueous solution. We report that mesocrystals of calcite with magnesium content of about 20 mol % can be obtained from the phase transformation of magnesian amorphous calcium carbonate (Mg-ACC) in lipid solution. The limited water content on the Mg-ACC surface would reduce the extent of the dissolution-reprecipitation process and bias the phase transformation pathway toward solid-state reaction. We infer from the selected area electron diffraction patterns and the dark-field transmission electron microscopic images that the formation of Mg-calcite mesocrystals occurs through solid-state secondary nucleation, for which the phase transformation is initiated near the mineral surface and the crystalline phase propagates gradually toward the interior part of the microspheres of Mg-ACC.

High‐Magnesium Calcite Mesocrystals: Formation in Aqueous Solution under Ambient Conditions

AbstractMesocrystals of high‐magnesian calcites are commonly found in biogenic calcites. Under ambient conditions, it remains challenging to prepare mesocrystals of high‐magnesian calcite in aqueous solution. We report that mesocrystals of calcite with magnesium content of about 20 mol % can be obtained from the phase transformation of magnesian amorphous calcium carbonate (Mg‐ACC) in lipid solution. The limited water content on the Mg‐ACC surface would reduce the extent of the dissolution–reprecipitation process and bias the phase transformation pathway toward solid‐state reaction. We infer from the selected area electron diffraction patterns and the dark‐field transmission electron microscopic images that the formation of Mg‐calcite mesocrystals occurs through solid‐state secondary nucleation, for which the phase transformation is initiated near the mineral surface and the crystalline phase propagates gradually toward the interior part of the microspheres of Mg‐ACC.

Effect of Cement on the Drying–Wetting Paths and on Some Engineering Properties of a Compacted Natural Clay from Oran, Algeria

The purpose of this paper is to study the effect of cement on the consistency limits, drying–wetting paths, hydraulic conductivity measured by oedometer and triaxial tests in the short and long terms, and durability during wetting and drying cycles on untreated and treated samples. The compressive strength of the soil was also measured at the end of the durability tests. The study was carried out on samples of the natural swelling clay of Mers El Kebir (Algeria) compacted under Standard Optimum Proctor conditions and treated with different percentages of cement. The results show that the liquid limit decreases, and the plastic limit increases with the amount of cement. In the case of the drying–wetting path, a decrease in the shrinkage limit suction and an increase in the shrinkage limit water content were observed when the percentage of added cement increased. The tests conducted to evaluate the hydraulic conductivity of the treated soil show an increase in permeability just after the treatment, followed a decrease as a function of the curing time. From the durability tests, it could be observed that the clayey soils stabilized by cement exhibit high performance and survive 12 cycles of wetting–drying testing.

Specific ion effects on surrogate compatibility indices of bentonite for hydraulic barrier applications

Bentonites are extensively used in waste containment facilities for controlling the migration of contaminants. The performance assessment of these facilities requires study on long-term hydraulic behaviour of proposed barrier material in the presence of different salts. Liquid limit water content and equilibrium sediment volume (ESV) of clays in the presence of different salt electrolytes are recognised to be the surrogate compatibility indices for understanding the long-term hydraulic behaviour of bentonites. The present paper provided a detailed analysis of influencing parameters on the behaviour of potential clay barrier through these two surrogate compatibility tests. The influence of different pore-fluid parameters, such as electrolyte concentration and specific ion effects on the behaviour of Indian bentonite was presented. The controlling mechanism of these two indices in the presence of different pore-fluid parameters was brought out. A relationship was obtained between the liquid limit water content and ESV data from the present study and the literature studies on different clays. Similarly, a good correlation was found between these indices and equilibrium hydraulic conductivity in the presence of different salt concentrations and different hydrated cation radii.

Evaluation for intrinsic compressibility of reconstituted clay using liquid limit, initial water content and plasticity index

To establish the evaluation method of intrinsic compressibility, oeodemter test was performed on Zhuozi clay and Wuqing clay and some other test data of various kinds of reconstituted clays were collected from the previous literatures. The compressibility constants (void ratio at vertical stress of 100 kPa) and (compression index) are widely recognised as indicators of intrinsic compressibility. Therefore, the influencing mechanisms of index properties can be investigated by establishing correlations with and . It has been found that and have linear relationships with liquid limit and normalised initial water content. Therefore, and can be quantitatively evaluated in terms of liquid limit and initial water content. Since plasticity index is the third factor that can slightly affect intrinsic compressibility, it can be used to modify the calculated value of and . It is indicated that liquid limit, initial water content and plasticity index are all index properties that can affect intrinsic compressibility, based on which and can be calculated and finally the compression curves can be evaluated based on the intrinsic concept.

Characterizing extreme and oppressive heat waves in Illinois

AbstractHeat waves are characteristic features of summertime climate in the Midwest United States and can have significant agricultural, hydrological, and societal impacts. Historically, heat waves in the Midwest state of Illinois have been either extreme (high temperature and low humidity) or oppressive (high temperature and high humidity) in nature, but our knowledge of the factors determining which heat wave type occurs is limited. We use self‐organizing maps to classify synoptic‐scale atmospheric circulation patterns associated with oppressive and extreme heat events and analysis of variance to evaluate the atmospheric and land surface features responsible for differences in humidity that characterize the two. We find that the majority of extreme and oppressive heat events are associated with similar synoptic‐scale atmospheric conditions. Additionally, both locally evaporated moisture and advected moisture sources were important for determining which of the two heat wave types occurred. Specifically, oppressive heat waves were characterized by abundant antecedent precipitation, surplus soil moisture, and elevated evapotranspiration and related atmospheric humidity. Lower humidity levels during extreme heat wave events were driven by relative reductions in evapotranspiration due to limited soil water content. Overall, our results suggest that the onset of heat waves in Illinois is primarily driven by circulation features in the upper atmosphere; however, the distinction of extreme or oppressive heat wave is due to differences in boundary layer humidity, driven in part by land surface moisture availability for evapotranspiration.

Physiological markers of stress susceptibility in maize and triticale under different soil compactions and/or soil water contents

ABSTRACTDifferences between two maize and two triticale genotypes grown in low soil compaction (LSC), moderate soil compaction (MSC) and severe soil compaction (SSC) and with a limited (D) or excess (W) soil water content were observed as a decrease in shoot (S) and root (R) biomass, leaf greening (SPAD) and increase in membrane injury (LI), root and leaf water potential (ψ), photosynthesis (Pn), transpiration (E) and stomata conductance (gS). Close correlations between ψL and ψR, and between differences ψL and ψR (Δψ) were found. Drought or waterlogging with LSC conditions in both maize genotypes resulted in higher WUE than in control plants (LSC C), but under the SSC WUE declined. However, for triticale differences in WUE, between treatments were small and insignificant. In general, changes in markers were greater for genotypes sensitive to the soil compaction (Ankora, CHD-12) than in resistant ones (Tina, CHD-247) and were higher in seedlings grown under SSC conditions.Abbreviations: ψR, ψL: root and leaf water potential; C: control; D: drought; E: transpiration rate; FWC: field water capacity; gS: stomatal conductance; LSC, MSC, SSC: low, moderate and severe soil compaction; Pn: photosynthesis rate; W: waterlogging

Cosolvent Effects on Dechlorination of Soil-Sorbed Polychlorinated Biphenyls Using Bentonite Clay-Templated Nanoscale Zero Valent Iron.

Zero-valent iron synthesized using bentonite clay as a template (CZVI) was tested for its reactivity toward polychlorinated biphenyl (PCB) dechlorination in soil slurries. Aqueous-phase decachlorobiphenyl (PCB209) was rapidly dechlorinated by CZVI with a reaction rate 10 times greater than that by conventional nanoscale zerovalent iron. This superior reactivity was due largely to the nanoscale size (∼0.5 nm) of the ZVI particles located in the clay galleries. In soil slurries where PCB209 was strongly soil-bound, adding ethanol as an organic cosolvent led to increased PCB209 desorption into the liquid phase, thereby enhancing the PCB209 dechlorination with CZVI. The more effective PCB209 dechlorination in such a cosolvent system also promoted the subsequent stepwise dechlorinative process, leading to a relatively more removal of chlorine in the product mixture. The dechlorination became more rapid as the ethanol fraction increased from 10% to 50%, due apparently to the increasingly greater PCB209 desorption and thus facilitated contact with CZVI. Further increase in ethanol fraction above 50% led to an insignificant enhancement in degradation rate, due partially to attenuated contact of PCB209 with CZVI and reduced proton source from limited water content in the liquid. It is suggested that addition of organic cosolvents may make CZVI potentially useful for remediation of soils containing halogenated organic contaminants.

Plant-soil Water Status-induced Changes in Physiological and Biochemical Properties of Yarrow

As medicinal plants are generally collected from the wild flora, it is of fundamental importance to identify the optimum growth conditions for increasing the yield and quality potential of ex-situ cultivated plants. Effects of different soil water content [20, 40, 60 and 80% of water holding capacity (WHC)] on growth, physiology and biochemical profile of Achillea millefolium group-related cv. Proa were investigated in the present study. Alterations in drug herbage, chlorophyll content, quantum efficiency of photosystem II, essential oil rate and composition, proline content and lipid peroxidation, antioxidant activity and flavonoid content of the plants under different plant and soil water status were determined. Decrease in soil water status under 40% of WHC resulted in degradation of chlorophyll pigments, reduction in photochemical efficiency and lower dry matter production. The essential oil (EO) rate of cv. Proa was higher under limited and excessive water content of soil whereas the main component of EO, chamazulene, was negatively correlated with WHC of soil. Our results suggest a general trend of inverse correlation of antioxidant capacity and flavonoid content with essential oil rate in contrast to the positive correlation of these parameters with chamazulene content. The data obtained may serve as a basis of programming the optimum soil moisture conditions for successful cultivation of cv.Proa.

Toughness Limit: A Useful Index Property for Prediction of Compaction Parameters of Fine Grained Soils at Any Rational Compactive Effort

For establishing quick, practical and reliable criteria for effective control of field compaction, prediction of compaction parameters on the basis of laboratory tests—which are simple and less time consuming—are desirable. Through a review and analysis of reported literature on compaction characteristics of fine grained soils, it is shown that toughness limit-the water content at which soil state changes from a virtually non workable adhesive-plastic region to a workable tough-plastic region-bears a good correlation with optimum moisture content. The accuracy of optimum moisture content prediction is seen to improve when different correlation equations are used for low-to-medium plastic and highly plastic soils. At all energy levels studied, maximum dry unit weight is found to bear a good correlation with the dry unit weight at toughness limit water content. The range of workable or tough-plastic region has been identified as nearly 0.42 times the conventional plastic region as proposed by Atterberg. Thus the study also emphasises the combined influence of liquid limit and plastic limit on compaction parameters of fine grained soils at any rational compactive effort.

Applicability of Filter Design Criteria for Wet Core Embankment Dams in Wet Climates

Abstract In humid and rainy climates, many embankment dams are constructed with core materials, possessing moisture in excess of optimum compaction water content. Since internal erosion and piping are major culprits of embankment dam failures, it would be practically important to understand whether contemporary filter design criteria, which make no reference to moisture content or compaction ratio of soils, are applicable to wet-under compacted cores. In this treatment, 123 no erosion filter (NEF) tests were performed on eleven core materials with varying moisture contents and compaction ratios. Results suggest that proper filter functionality depends on moisture in excess of optimum, soil Plasticity Index, and D15/d85. With increase in excess moisture, a smaller D15/d85 is required for erosion prevention, insomuch as filters designed via recommended criteria, may become inadequate, when the core is excessively wet and under compacted. Generally speaking, D15/d85 ≤ 9 is reliable for cores with limited excess water content and compaction ratios over 95 %; whereas D15/d85 ≤ 7 should be applied for compactions above 90 % and moistures significantly beyond optimum.

Self-Organizing Anodization in Pure Molten O-H3PO4

In 1995 Masuda et al. reported on a straightforward anodization approach that allowed for the growth of self-organized vertically-aligned alumina nanopores.1 Since then, electrochemical anodization has been widely investigated as a most suitable way to fabricate one dimensional (1D) functional oxide structures.2 Highly-ordered architectures of several metal oxides were successfully formed by anodizing in aqueous acidic solutions (e.g., Al2O3),1 fluoride containing aqueous or organic solvents (e.g., TiO2, Ta2O5, ZrO2, HfO2, etc.),3,4 and hot glycerol electrolytes (e.g., Al2O3, Ta2O5, TiO2).5-7 With this contribution we introduce a class of anodizing electrolytes, based on pure ortho-phosphoric acid (i.e., o-H3PO4), that provides high aspect-ratio highly-ordered oxide nanostructures on some of the most challenging elements such as W, as well as on more common elements such as Al, Ti, Nb.8 We describe how to tailor the structure of the formed anodic oxides by adjusting a set of key electrochemical parameters such as the electrolyte temperature, its water content, the applied voltage, and the anodization time. We show that under suitable conditions, an ideal equilibrium is established between field-assisted passivation of the metal and oxide dissolution, this leading to the growth of the anodic oxide layers in a highly ordered fashion.Not only pure molten ortho-phosphoric acid but also other phosphorus-containing acids, namely, hot pure pyro- and poly-phosphoric acids, are able to establish the required self-organizing electrochemical conditions for the growth of ordered oxide structures. We propose that the role of the molten phosphate electrolyte is two-fold: i) it provides an environment with controlled and limited water content (that is the key oxidant), and ii) it provides phosphate ions that protect the anodic oxide from rapid dissolution, this allowing for a controlled growth of the metal oxide nanostructures.(1) Masuda, H.; Fukuda, K. Science 1995, 268, 1466; (2) Roy, P.; Berger, S.; Schmuki, P. Angew. Chem. Int. Ed. 2011, 50, 2904; (3) Assefpour-Dezfuly, M. J. Mater. Sci. 1984, 19, 3626; (4) Kowalski, D.; Kim, D.; Schmuki, P. Nano Today 2013, 8, 235; (5) Melody, B.; Kinard, T.; Lessner, P. Electrochem. Solid-State Lett. 1999, 1, 126; (6) Lu, Q.; Alcalá, G.; Skeldon, P.; Thompson, G.; Graham, M. .; Masheder, D.; Shimizu, K.; Habazaki, H. Electrochim. Acta 2002, 48, 37; (7) Kim, D.; Lee, K.; Roy, P.; Birajdar, B.; Spiecker, E.; Schmuki, P. Angew. Chemie Int. Ed. 2009, 48, 9326; (8) Altomare, M.; Pfoch, O.; Tighineanu, A.; Kirchgeorg, R.; Lee, K.; Selli, E.; Schmuki, P. J. Am. Chem. Soc. 2015, 137, 5646. Figure 1

COMPARISON OF CONSOLIDATION CURVES FOR REMOLDED MUD VOLCANO OF SIDOARJO, INDONESIA

Sidoarjo mud volcano (Lusi) is one of the most challenging problems regarding to the compressibility of fine grained soils in Indonesia. Understanding about compressibility behavior is essential to construct appropriate remediation program for this problems. Consolidation test has been conducted to investigate the compressibility behavior of Lusi mud volcano. In this study, the laboratory test result is compared with estimated value derived from several empirical equations. A simple equation can be used to predict e-log σ’ curve very well by using the correlation between initial void ratio (e0) and void ratio corresponding to unit pressure (e1); and correlation between compression index (Cc) and physical properties of soils, such as liquid limit (wL) or natural water content (wn). This equation predict better than other available equations in literature when compared with laboratory test of Lusi mud volcano.

BEYOND THE “LEAST LIMITING WATER RANGE”: RETHINKING SOIL PHYSICS RESEARCH IN BRAZIL

As opposed to objective definitions in soil physics, the subjective term “soil physical quality” is increasingly found in publications in the soil physics area. A supposed indicator of soil physical quality that has been the focus of attention, especially in the Brazilian literature, is the Least Limiting Water Range (RLL), translated in Portuguese as "Intervalo Hídrico Ótimo" or IHO. In this paper the four limiting water contents that define RLLare discussed in the light of objectively determinable soil physical properties, pointing to inconsistencies in the RLLdefinition and calculation. It also discusses the interpretation of RLL as an indicator of crop productivity or soil physical quality, showing its inability to consider common phenological and pedological boundary conditions. It is shown that so-called “critical densities” found by the RLL through a commonly applied calculation method are questionable. Considering the availability of robust models for agronomy, ecology, hydrology, meteorology and other related areas, the attractiveness of RLL as an indicator to Brazilian soil physicists is not related to its (never proven) effectiveness, but rather to the simplicity with which it is dealt. Determining the respective limiting contents in a simplified manner, relegating the study or concern on the actual functioning of the system to a lower priority, goes against scientific construction and systemic understanding. This study suggests a realignment of the research in soil physics in Brazil with scientific precepts, towards mechanistic soil physics, to replace the currently predominant search for empirical correlations below the state of the art of soil physics.

Physicochemical changes of maize starch treated by ball milling with limited water content

A granular maize starch with limited amounts of water was ball milled, and the structural changes were investigated. The chemical changes were analyzed in terms of amylose content, hydroxyl and carbonyl contents, and intrinsic viscosity. The granule or aggregation structures were characterized by X‐ray diffraction, differential scanning calorimetry, laser particle diameter analyzer, and scanning electron microscope. The gelatinization and paste property were measured with a Rapid Visco‐Analyzer. Under the ball‐milling conditions of 25 wt% water content based on the starch, a ball diameter of 15 mm, a weight ratio of ball to starch at 4:1, and milling time of 3 h, the ball‐milled starch granules did not have apparent gelatinization or agglomeration. After the ball milling, the system temperature increased by 25.5°C. The resultant starch granules displayed a flat‐ or oval‐shaped pattern without edges, and their particle size slightly increased with a narrower size distribution. The ball‐milled starch was mildly oxidized, and the intrinsic viscosity and the amylopectin content decreased a little. The crystallinity of granules decreased greatly from 31.1 to 13.0%, concurrent with a decrease in the thermal transition enthalpy. The pasting temperature increased, while the peak viscosity, breakdown, and setback greatly decreased. Our results indicated that the limited additional water in the ball‐milling process helps expand the amorphous region in starch granules and could reduce damage level of starch molecules and granules.

An Approach to Swelling Potential of Cohesive Soils: Avcilar-Esenyurt Example

Cohesive soil exhibits various degrees of swelling potential due to their clay contents and minerals. Many studies have been conducted to determine the degree of swelling of cohesive soil in the literature. These studies are related with the percentage of clay and colloid, plasticity index, shrinkage limit, activity, liquid limit, the water content and absorption and some of them give tables and others give graphics. In this study, the swelling potential of cohesive soil depending on liquid limit and natural water content were investigated. The graphical relation in literature was solved and a general equation between the water content and liquid limit of cohesive soil was determined for predicting swelling percentage. It is understood that the relation of swelling percentage between water content and liquid limit is not logarithmic as given in the literature, but it is an exponential equation with a -0.187w power constant N. The proposed methodology was applied to cohesive soil between Avcilar and Esenyurt. In literature classifications for swelling potential are variable and these definitions are inconsistent with each other. Whereas reliable numerical values for swelling are obtained by the proposed approach of swelling potential associated with clays water content.