Influence of clod size and water content on gas permeability of a compacted loess

2014 ◽  
Vol 51 (12) ◽  
pp. 1468-1474 ◽  
Author(s):  
T.L.T. Zhan ◽  
Y.B. Yang ◽  
R. Chen ◽  
C.W.W. Ng ◽  
Y.M. Chen
Keyword(s):  
Water Content ◽  
Power Function ◽  
Soil Structure ◽  
Gas Permeability ◽  
High Water ◽  
Degree Of Saturation ◽  
Northwestern Region ◽  
Water Contents ◽  
Compacted Loess ◽  
Compaction Degree

The northwestern region of China is mainly semi-arid to arid and loess is ubiquitous. This natural resource has considerable potential to be transformed into earthen final covers for local landfills, but first its suitability must be ascertained through extensive tests. In this study, a device was developed to measure the gas permeability of unsaturated compacted loess specimens. Experiments were carried out to investigate the influence of clod size, compaction water content, and post-compaction water content on the gas permeability of the compacted loess. To maintain an identical soil structure, the post-compaction water content was changed using the osmotic technique. It was found that the compaction water content and resultant soil clod size exerted a combined effect on the gas permeability such that, at low water contents, the gas permeability remained fairly constant, but at high water contents the clods became relatively large, and the effect of the clod size dominated the water blockage effect from increasing water content. For specimens with identical soil structure, the gas permeability decreased with the increasing post-compaction degree of saturation at an accelerated rate. A power function is proposed to predict the relationship between the gas permeability normalized by the porosity function of the Kozeny–Carmen model and the post-compaction degree of saturation. Analysis of the experimental data indicates that the parameters for the power function still depend on the porosity of the compacted loess, particularly at high degrees of saturation.

An Equilibrium Model of Leaf Water Potentials Which Separates Intra- and Extracellular Potentials

1975 ◽  
Vol 2 (3) ◽  
pp. 253 ◽  
Author(s):  
B Acock
Keyword(s):  
Water Content ◽  
Turgor Pressure ◽  
Bound Water ◽  
Leaf Tissue ◽  
High Water ◽  
Leaf Water ◽  
High Water Content ◽  
Pressure Potential ◽  
Matrix Bound ◽  
Water Contents

A model is proposed which makes it possible to estimate the intracellular turgor pressure potential, intracellular osmotic plus matric potential, and intra- and extracellular soIution fractions of water in leaf tissue at any water content. The model requires only the data normally collected with a thermocouple psychrometer: total water potential of live and dead (cells ruptured) tissue at various known water contents. The major assumptions are that (1) the total potential of water in the solution fraction in any part of the tissue multiplied by the volume of water is constant; (2) extracellular water experiences no pressure potential; (3) matrix-bound water is held only by matric forces and contains no solute; (4) the solution fraction of the intracellular water is constant at high water content; and (5) matrix-bound water content is constant over the range of leaf water contents normally examined. The models developed to deal with pressure bomb data are examined critically and doubts are cast on the validity of some of their assumptions.

STUDIES IN TREE PHYSIOLOGY: I. GENERAL INTRODUCTION. WATER CONTENTS OF CERTAIN CANADIAN TREES

1939 ◽  
Vol 17c (12) ◽  
pp. 460-482 ◽  
Author(s):  
R. Darnley Gibbs
Keyword(s):  
Water Content ◽  
Populus Tremuloides ◽  
Weather Conditions ◽  
High Water ◽  
High Water Content ◽  
White Pine ◽  
General Introduction ◽  
Very High ◽  
Considerable Loss ◽  
Water Contents

Previous work by the author on the water contents of Canadian trees is reviewed and followed by a brief discussion of questions yet to be answered.In Betula alba v. papyrifera, in at least the young parts of B. alba v. pendula laciniata, in B. populifolia, and in several sizes of Populus tremuloides, there is a marked seasonal rhythm in water content. The maximum is at leaf opening, the minimum at leaf fall. In poplar but not in birch there is a very high water content in December. During winter a considerable loss of water may occur. A winter loss is shown also by the wood of hemlock and larch and by twigs and leaves of white pine and hemlock. Losses from leaves are surprisingly small.The behaviour of B. populifolia has been studied for more than three years, and differences have been correlated with observations on weather conditions. Experimental work on movement of water in this species during winter is inconclusive. This work continues.

Isothermal micro-calorimetry: a tool to predict seed longevity?

2006 ◽  
Vol 16 (2) ◽  
pp. 89-96 ◽  
Author(s):  
Fiona R. Hay ◽  
Michael A.A. O'Neill ◽  
Anthony E. Beezer ◽  
Simon Gaisford
Keyword(s):  
Heat Flow ◽  
Water Content ◽  
High Water ◽  
Seed Longevity ◽  
Total Heat ◽  
Short Term ◽  
Seed Ageing ◽  
Rate Kinetics ◽  
Residual Power ◽  
Water Contents

This paper describes the exploratory use of isothermal micro-calorimetry (IMC) to measure directly the heat flow produced as seeds age. Heat flow was recorded in primed and non-primed (control) seeds of Ranunculus sceleratus L., aged in a micro-calorimeter at 35°C at three different seed water contents [c. 0.12, 0.075 and 0.045 g H2O (g dw)−1]. The rate of heat flow and total heat generated (an indicator of extent of reaction) were generally greater in control seeds, which aged at a faster rate, than in primed seeds. Total heat generated over a given period also increased with increasing water content. The power–time curves did not indicate first- or second-order rate kinetics, consistent with the probability that seed ageing is complex and involves a number of reactions. Even after the capacity to germinate had ceased, there was a residual power signal. As a method, IMC gave consistent results using independent samples at different times. Therefore, short-term experiments at relatively high water contents and/or temperatures may have the potential to predict the relative longevity of seed-lots, at least within a species.

Effect of Compaction Degree on Soil-Water Characteristic Curve of Chongming Clay

2011 ◽  
Vol 90-93 ◽  
pp. 701-706
Author(s):  
Jing Song Qian ◽  
Hang Lu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Filter Paper ◽  
Characteristic Curve ◽  
Liquid Limit ◽  
Degree Of Saturation ◽  
Paper Test ◽  
Soil Water Characteristic Curve ◽  
Gravimetric Water Content ◽  
Compaction Degree

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. It is a convenient method to predict water content in the subgrade using the curve. But in the field tests of subgrades, the compaction degree of soil became lower with time than initially designed. With the purpose of finding out effect of compaction degree on soil-water characteristic curve, a study to the SWCC (soil-water characteristic curve) of Chongming low liquid limit clay using filter paper method was carried out and is presented in this paper. Specimens of different water contents were prepared by absorbing different amount of water, in order to better simulate the process of wetting of subgrade soil. After the filter paper test, the soil-water characteristic curve was fitted with two models, and then the effect of compaction degree on the curve was analyzed. The figures show that the compaction degree of the specimen will decrease with higher water content, and from the gravimetric water content-matric suction curve, it is found that compaction degree has an effect on air-entry value and water storage capacity.

Aqueous Diffusion in Repository and Backfill Environments

1992 ◽  
Vol 294 ◽  
Author(s):  
James L. Conca ◽  
Mick Apted ◽  
Randy Arthur
Keyword(s):  
Diffusion Coefficient ◽  
Water Content ◽  
Surface Diffusion ◽  
High Water ◽  
Double Layers ◽  
Point Contacts ◽  
Simple Diffusion ◽  
Time Period ◽  
Engineered Systems ◽  
Water Contents

ABSTRACTAqueous diffusion coefficients have been experimentally determined in a variety of porous/fractured geologic and engineered media. For performance assessment applications, the purely diffusive flux must be separated from retardation effects. The simple diffusion coefficient, D, does not include any transient chemical effects, e.g., sorption, which lower the diffusion coefficient for some finite time period until equilibrium is reached. D is primarily a function of volumetric water content, θ, and not material characteristics. At high water contents, D gradually declines as water content decreases, from 10−5 cm2/sec at θ ∼ 50% to 10−7 cm2/sec at θ ∼ 5%, followed by a sharp decline to 10−10 cm2/sec at θ ∼ 0.5%. Although surface diffusion has a strong experimental basis in the transport of gases along metal surfaces, experimental evidence for aqueous geologic/backfill/engineered systems strongly indicates that surface diffusion is not important, even in bentonite, because of the extremely poor connectivity among electric double-layers and the extremely low diffusivities and high ∂C/∂x at small area/point contacts which more than negate the increased flux along intragrain surfaces.

scholarly journals Viability and germination of Scots pine seeds after freezing of harvested cones in vitro

2016 ◽  
Vol 46 (8) ◽  
pp. 1035-1041
Author(s):  
Markku Nygren ◽  
Katri Himanen ◽  
Hanna Ruhanen
Keyword(s):  
Water Content ◽  
Scots Pine ◽  
Seed Viability ◽  
High Water ◽  
Logistic Function ◽  
High Water Content ◽  
Maturation Stage ◽  
Freezing Treatment ◽  
Water Contents

Scots pine (Pinus silvestris L.) cone and seed water contents were analyzed in two consecutive seasons during maturation stage in the autumn and in January and March before seed dispersal. Cones with different water contents were subjected to 2 h of freezing at −30 °C, and seed viability and laboratory germination of seeds from individual cones after treatment were analyzed. Seed water content could be well predicted with the measurement of the cone water content, and the general relationship between these two could be described with a generalized logistic function. On average, the water content of cones was 5%–10% units higher than the seeds inside them. The higher the cone water content at the onset of freezing treatment, the higher the proportion of seeds with apparent damage (based on visual inspection of seeds using X-ray images) in that particular cone. High water content in cones also resulted in decreased germination after freezing treatment. The critical cone water content for 50% germination after freezing at −30 °C was approximately 31.3% (fresh mass basis). This corresponds to 21.6% water content in seeds.

scholarly journals Experimental Study on Dynamic Tensile Failure of Sandstone Specimens with Different Water Contents

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Ming Li ◽  
Gang Lin ◽  
Wei Zhou ◽  
Xianbiao Mao ◽  
Lianying Zhang ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Water Content ◽  
Water Saturation ◽  
Water Injection ◽  
High Water ◽  
Tensile Failure ◽  
High Water Content ◽  
Dynamic Tensile Strength ◽  
Macroscopic Crack ◽  
Water Contents

Understanding the effect of water saturation on dynamic failure of rocks is of great importance to tunnel excavation at water-rich coal mines and prevention of rock bursts by water injection. Dynamic Brazilian disc tests are performed to study mechanical behaviour of sandstones in this paper. The results indicate that water saturation significantly weakens the dynamic tensile strength of sandstones and increases the specimen strain at which the specimen fails. The damage degree of sandstones reduces gradually with increasing water contents. Failure of the sandstone specimen includes the crack initiation at the center of the specimen, macroscopic crack propagation, and stretch of the macroscopic crack through the specimen. In addition, parallel macroscopic crack propagation is found in the specimen with a low water content. From the observation of fracture sections, microstructures are compact in the specimen with high water contents. This is due to the swell of the kaolinite in the specimen after water saturation. The failure mechanism of microstructures is typical brittle failure in the specimen with a high water content, whereas ductile fracture is found in the specimen with a low water content. Different failure processes of microstructures lead to the differences between mechanical properties and macroscopic failure characteristics of the specimens with various water contents.

scholarly journals Water loss during dynamic recrystallization of Moine thrust quartzites, northwest Scotland

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 557-561
Author(s):  
Andreas K. Kronenberg ◽  
Kyle T. Ashley ◽  
Matthew K. Francsis ◽  
Caleb W. Holyoke III ◽  
Lynna Jezek ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Water Content ◽  
Water Concentration ◽  
Inverse Correlation ◽  
High Water ◽  
Dislocation Creep ◽  
Molecular Water ◽  
Reduced Water ◽  
Water Contents ◽  
Absorption Measurements

Abstract Infrared absorption measurements of molecular water in sheared Cambrian quartzites in the footwall to the Moine thrust reveal a decrease in water content from 4080 to 1570 ppm with increasing recrystallization traced toward the overlying thrust at the Stack of Glencoul in northwest Scotland. These results are contrary to the expected correlation between shear strain and water content for quartz deformed by dislocation creep and water-weakening processes. The observed inverse correlation indicates that fluid inclusions and hydrous defects within grains were lost by mobile grain boundary sweeping and grain boundary diffusion. Although reduced water contents might lead to hardening as chemical weakening is diminished, quartz mylonites in the immediate footwall (5 mm) to the thrust are characterized by intense strain localization and contain the least water, and there is little evidence of shear zone widening. Water weakening appears to have been important throughout the quartz mylonites, controlled by the presence of water, not by water concentration. Fluids present within relict inclusions and at grain boundaries may have governed the high water fugacities critical for water weakening.

Nitrous oxide production and sources in response to a simulated fall-freeze-thaw cycle

2020 ◽  
Author(s):  
Sisi Lin ◽  
Guillermo Hernandez Ramirez
Keyword(s):  
Climate Change ◽  
Water Content ◽  
Soil Water ◽  
High Water ◽  
Organic N ◽  
High Water Content ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Water Contents

<p>Thaw-induced N<sub>2</sub>O emissions have been shown to account for 30-90% of N<sub>2</sub>O emissions in agricultural fields. Due to the climate change, increased precipitatio is expected in fall and winter seasons for certain regions. As a result, this would in turn enhance the thaw-induced N<sub>2</sub>O emissions and aggravate climate change. A mesocosm study was conducted to investigate N<sub>2</sub>O production and sources from soils under elevated soil moisture contents in response to a simulated fall-freeze-thaw cycle. Treatments included two levels of N addition (urea versus control) and two different management histories [with (SW) and without (CT) manure additions]. Our results showed that at least 92% of the N<sub>2</sub>O emissions during the study were produced during the simulated thawing across all treatments. The thaw-induced N<sub>2</sub>O emissions increased with increasing soil water content. The fall-applied urea increased the soil-derived N<sub>2</sub>O emissions during thawing, indicating an excessive mineralization of soil organic N. Compared to the CT soils, the SW soils induced more soil-derived N<sub>2</sub>O emissions. This could be because the SW soil had more easily decomposable organic matter which was likely due to historical manure additions. Regarding to the daily primed N<sub>2</sub>O fluxes, different soil water contents impacted the dynamics of daily priming effect. At the high water content, the soils experienced a shift in daily primed N<sub>2</sub>O fluxes from positive to negative and eventually back to positive throughout the simulated thawing, while the soils at lower water contents underwent positive primed fluxes in general. The shift in daily primed fluxes was probably driven by the preference of soil microbes on the labile N substrates. When the microbes switched from easily to moderately decomposed substrates (e.g., from dissolved organic N to plant residuals), they started to uptake inorganic N from the soil due to a relatively high C:N ratio of plant residuals. Therefore, a net N immobilization and negative primed N<sub>2</sub>O production occur in the short term in the soils at the high water content.</p>

The nature of changes in bulk density with water content in a cracking clay

Soil Research ◽  
1977 ◽  
Vol 15 (1) ◽  
pp. 27 ◽  
Author(s):  
RD Berndt ◽  
KJ Coughlan
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Three Dimensional ◽  
Small Diameter ◽  
High Water ◽  
Density Relationship ◽  
Actual Field ◽  
Diameter Core ◽  
The Relationship ◽  
Water Contents

The effect of changing water content on the bulk density of undisturbed cores of a cracking clay was examined in laboratory experiments. The results were compared with the relationship between bulk density and water content established by core sampling the same soil in the field. Over the water content range measured in the field soil, the laboratory cores shrank three-dimensionally and normally. Small departures from normal shrinkage were attributed to the formation of cracks within the cores, and to the occurrence of some structural shrinkage in cores previously wet to high water contents. Swelling of cores was approximately three-dimensional, except for some unconfined swelling which occurred in the core surface. Unidimensional swelling was induced by confining dry cores to reduce the void ratio before wetting. Subsequent shrinkage was three-dimensional, indicating that the soil particles were reoriented during the unidimensional swelling phase. While the laboratory measurements showed that the soil volume changes were essentially three-dimensional and normal, the field data indicated that unidimensional shrinkage occurred at water contents greater than 0.47 g g-1. These field results were attributed to sampling inaccuracies associated with the use of a small-diameter core sampler, the actual field bulk density relationship being considered three-dimensional.

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