ALTERATIONS OF SOIL STRUCTURE UPON FREEZING AND THAWING AND SUBSEQUENT DRYING

1968 ◽  
Vol 48 (2) ◽  
pp. 193-197 ◽  
Author(s):  
W. C. Hinman ◽  
Frederick Bisal
Keyword(s):  
Moisture Content ◽  
Soil Structure ◽  
Room Temperature ◽  
Clay Soil ◽  
Soil Aggregates ◽  
Initial Moisture Content ◽  
Aggregate Size ◽  
Freezing And Thawing ◽  
Initial Size ◽  
Freeze Dried

A laboratory investigation of a clay soil indicated that the percentage of aggregates < 1 mm in diameter might be increased, decreased or unaffected by freezing and thawing depending on the initial moisture content, the initial size of soil aggregates and the method of drying the sample. Little or no changes in aggregate size occurred if the initial moisture content was at 15 atmospheres. At 0.1 atm, aggregates which were initially coarse (> 4 mm) tended to break down slightly when exposed to alternate freezing and thawing followed by air-drying at room temperature. On the other hand, a substantial decrease in aggregates < 1 mm in diameter occurred when aggregates which were originally fine received the same sequence of treatments. However, if the samples were freeze-dried following the same treatments, all aggregates were reduced to < 1 mm in diameter. Similar trends were established with samples which were continuously frozen and when the initial moisture content was at 0.33 atm, although the magnitude of the change was much smaller. It is proposed that forces engendered during freezing disrupt aggregates, but this process is reversed during thawing and drying at room temperatures.

Some factors affecting compacted clay swelling

1970 ◽  
Vol 7 (1) ◽  
pp. 79-91 ◽  
Author(s):  
A. Yevnin ◽  
D. Zaslavsky
Keyword(s):  
Moisture Content ◽  
Volume Change ◽  
Empirical Equation ◽  
Clay Soil ◽  
Initial Density ◽  
Initial Moisture Content ◽  
Swelling Pressure ◽  
Compacted Clay ◽  
Factors Affecting ◽  
Applied Loading

Volume change after saturation was determined on specimens of a statically compacted clay soil. It was found that density after swelling increases linearly with increasing initial density, initial moisture content, and increasing logarithm of applied loading pressure. An empirical equation with five coefficients and a constant, found with the aid of a computer, represents the results with a coefficient of correlation close to 1. An equation for the swelling pressure was also obtained from this equation. Results of specimens which consolidated did not fit the lines obtained for swelling. The relationships obtained were explained by the influence of particle reorientation and moisture content on swelling tendency.

scholarly journals Experimental Study on the Effect of Freezing and Thawing on the Shear Strength of the Frozen Soil in Qinghai-Tibet Railway Embankment

2022 ◽  
Vol 2022 ◽  
pp. 1-12
Author(s):  
B. Wang ◽  
J. H. Gao ◽  
Y. Q. Wang ◽  
X. J. Quan ◽  
Y. W. Gong ◽  
...  
Keyword(s):  
Growth Rate ◽  
Internal Friction ◽  
Moisture Content ◽  
Initial Moisture Content ◽  
Friction Angle ◽  
Frozen Soil ◽  
Internal Friction Angle ◽  
Freezing Process ◽  
Dry Density ◽  
Freezing And Thawing

The direct shear tests of different dry density and moisture content samples at different temperatures of the frozen soil in the Qinghai-Tibet Railway embankment between Tanggula South and Anduo section were carried out to analyze the influence rules of each experimental factor on the mechanical properties of frozen soil during the freeze-thaw process. The results show the following. (1) When the frozen soil temperature is below 0°C and continues to drop during the freezing and thawing process, each sample shows the law of a significant increase in cohesion and a slight decrease in the internal friction angle. In the meantime, the cohesion obtained during the thawing process of the sample at the same temperature point is higher than that obtained during the freezing process. In contrast, the internal friction angles exhibit an opposite law, where the internal friction angle during the melting process is lower than the internal friction angle during the freezing process. After freezing-thawing action, it deserves to be mentioned that the cohesion increases slightly while the internal friction angles present a slight decrease trend compared to the initial state. (2) With the decrease in temperature and the gradual increase in cohesion, the temperature curve can be divided into a fast-growing section from 0 to −2°C, a slow-growing section from −2 to −8°C, and a second fast-growing section from −8 to −10°C owing to the combined effect of the pressure-thawing action and ice-water phase change. In addition, the rate of decrease in the internal friction angle also shows a similar pattern. (3) The cohesion and the internal friction angle of samples both tend to increase first and then decrease with the rise of the initial moisture content, and the critical initial moisture content is near the optimal moisture content of 15%. (4) Both the cohesion and the internal friction angle of the samples increase with dry density growth. The growth rate of cohesion will gradually increase as the temperature decreases. Moreover, the growth rate of cohesion of low dry density samples is more susceptible to temperature, while the internal friction angle growth rate is not affected by temperature.

scholarly journals EFFECTS OF INITIAL MOISTURE CONTENT ON THE PRODUCTION AND QUALITY PROPERTIES OF SOLID BIOFUEL

2015 ◽  
Vol 55 (5) ◽  
pp. 335 ◽  
Author(s):  
Miloš Matúš ◽  
Peter Križan ◽  
Juraj Beniak ◽  
Ľubomír Šooš
Keyword(s):  
Moisture Content ◽  
Room Temperature ◽  
Initial Moisture Content ◽  
Calorific Value ◽  
Quality Properties ◽  
Moisture Expansion ◽  
Solid Biofuel ◽  
Effect Of Moisture ◽  
Physical Changes

The moisture content of densified biomass is a limit parameter influencing the quality of the solid biofuel. It influences its calorific value, density, mechanical strength and dimensional stability as well as the production process of this biofuel. The paper deals with the experimental research of the effect of moisture content of densified material on the final quality of biofuel in the form of logs. Experiments based on the single-axis densification of spruce sawdust were realized by hydraulic piston press, where the densified logs were produced under room temperature. The effect of moisture content on the quality properties of the logs, including density, change of moisture, expansion and physical changes, were studied. The results show the necessary moisture ranges for producing good-quality logs. The experiments were evaluated and the moisture content of the tested material was optimized to achieve the optimum value for the best quality of the solid biofuel.

Effects of cyclic freezing and thawing on volume changes and permeabilities of soft fine-gained soils

1996 ◽  
Vol 33 (4) ◽  
pp. 529-537 ◽  
Author(s):  
K D Eigenbrod
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Maximum Volume ◽  
Freezing And Thawing ◽  
Volume Changes ◽  
One Dimensional ◽  
Freeze Thaw ◽  
Fine Grained ◽  
Liquidity Index ◽  
Thaw Consolidation

Soft, fine-grained soils were exposed to cyclic one-dimensional, open-system freezing and thawing, resulting in maximum volume changes of up to 30%, depending on the initial moisture content and plasticity of the clay as well as on the rate of freezing. A linear relationship between the net volume changes subsequent to freezing and thawing and the liquidity index prior to freezing and thawing was obtained. This correlation is not unique, but depends on rate and mode of freezing. Thus, settlements from freeze–thaw consolidation in the field can be predicted from such tests if the rate and mode of freezing are the same as in the field. During cyclic freezing and thawing the soils became fissured and jointed, resulting for most clays in large increases in their bulk permeabilities, which increased with an increasing number of freeze–thaw cycles, often by more than two orders of magnitude. For some materials, however, little change in permeability occured. Key words: cyclic freeze–thaw, clays, freeze–thaw consolidation, permeability, volume changes.

SPECTRAL ANALYSIS OF MICROPENETROMETER DATA TO CHARACTERIZE SOIL STRUCTURE

1985 ◽  
Vol 65 (4) ◽  
pp. 789-804 ◽  
Author(s):  
C. D. GRANT ◽  
B. D. KAY ◽  
P. H. GROENEVELT ◽  
G. E. KIDD ◽  
G. W. THURTELL
Keyword(s):  
Spectral Analysis ◽  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Spatial Separation ◽  
New Approach ◽  
Low Resistance ◽  
Loose Packing ◽  
Tip Resistance ◽  
Resistance To Penetration

A micropenetrometer with a diameter similar in magnitude to that of a root is capable of measuring variations in tip resistance over distances as small as 0.1 mm. Measurements at this scale offer the potential of characterizing zones of high resistance to penetration and the frequency of occurrence of zones of low resistance which could be exploited by a growing root. Spectral analysis provides a new approach to characterizing soil structure and has been applied to the micropenetrometer tip resistance profiles obtained from beds of aggregates. Nine different aggregate size ranges were considered; the aggregate diameters varied from less than 0.36 mm to 6.4–12.8 mm. The analyses indicate that larger aggregates are more resistant to penetration. In addition, comparison of variance spectra among several of the aggregate sizes reveals information on the structural make up of soil aggregates, namely that larger aggregates are made up of smaller "component" aggregates which offer higher resistance when they occur in large aggregates than when they occur individually in loose packing. The use of spectral analysis also appears to provide information on the spatial separation of zones of low resistance which correlate with aggregate size if the aggregate diameters are larger than 1.6 mm. Key words: Soil strength, soil resistance to penetration, micropenetrometer, aggregate size

Bordered Pit Aspiration in the Wood of Cryptomeria Japonica in Relation to Air Permeability

IAWA Journal ◽  
1997 ◽  
Vol 18 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Tomoyuki Fujii ◽  
Youki Suzuki ◽  
Naohiro Kuroda
Keyword(s):  
Moisture Content ◽  
Cryptomeria Japonica ◽  
Initial Moisture Content ◽  
Air Permeability ◽  
Heartwood Formation ◽  
Permeability Measurement ◽  
Air Drying ◽  
Freeze Dried ◽  
Pit Membrane ◽  
Bordered Pits

Aspiration of bordered pits in Cryptomeria japonica (L. f.) D. Don was studied in relation to the air permeability in sapwood, transition zone wood, and heartwood. The percentage of aspirated pits relative to the total number of bordered pits with observable tori was determined in samples that were epoxy-embedded and thin sectioned. Air permeability of air-dried and freeze-dried wood samples was measured following the method described by Siau (1984). Pit membrane structure of air-dried and freeze-dried samples was investigated by scanning electron microscopy on split radial surfaces. It is proposed that pit aspiration progresses during heartwood formation as already reported, but the pit aspiration was frequently incomplete and the percentage varied between individuals. The pit aspiration percentage was not obviously related to the sample's initial green moisture content or heartwood color. The results from permeability measurement and SEM observation on air- and freeze-dried samples suggest that pit aspiration occurred in sapwood samples (the initial moisture content of which ranged from 200 to 300%) during air-drying and caused a significant decrease in permeability confirming the pit aspiration mechanism proposed by Hart and Thomas (1967). In the heartwood, encrustation of pit membranes prevented aspiration during air-drying.

Categories of soil structure based on mechanical behaviour and their evaluation using additions of lime and gypsum on a sodic Vertisol

Soil Research ◽  
1999 ◽  
Vol 37 (5) ◽  
pp. 903 ◽  
Author(s):  
K. Y. Chan ◽  
K. Y. Chan ◽  
A. R. Dexter ◽  
A. R. Dexter ◽  
D. C. McKenzie ◽  
...  
Keyword(s):  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Soil Aggregate ◽  
Tension Test ◽  
Wetting And Drying ◽  
The Matrix ◽  
Indirect Tension ◽  
Indirect Tension Test ◽  
Soil Behaviour

Measurements of soil aggregate strength were made using a simple crushing (indirect tension) test. The resulting values of strength were used to examine aspects of the internal structure of the soil aggregates. This was done using 2 methods: firstly, by studying the dependence of aggregate tensile strength on aggregate size; and secondly, by studying the variability of strength measurements made on aggregates of one size. Combination of the results from the 2 methods enables some new categories of soil behaviour to be defined. The new categories were evaluated using soil samples collected from a field experiment in which additions of lime and gypsum were made to a sodic Vertisol. The use of the new categories leads to the conclusion that the added compounds resulted in larger aggregates being weaker than the smaller aggregates. This was partly due to a greater amount of micro-cracking in the larger aggregates, and partly due to a greater weakening of the matrix within the larger aggregates. Both of these changes are consistent with the soil being more friable after the additions of the calcareous amendments. It was not possible to distinguish qualitatively between the effects of lime and gypsum. It is suggested that the amendments did not modify the soil structure directly, but that they increased the tendency of the soil to self-mulch in response to wetting and drying cycles.

Unsaturated water transmission characteristics of soils in relation to texture, aggregate size and initial moisture content

1989 ◽  
Vol 112 (2) ◽  
pp. 199-204
Author(s):  
M. C. Mundra ◽  
Raj Pal ◽  
R. S. Siyag ◽  
S. R. Poonia
Keyword(s):  
Moisture Content ◽  
Soil Texture ◽  
Sandy Loam ◽  
Initial Moisture Content ◽  
Aggregate Size ◽  
Loamy Sand ◽  
Clay Loam ◽  
Water Diffusivity ◽  
Unsaturated Hydraulic Conductivity ◽  
Water Transmission

SummaryTo study the effect of soil texture, aggregate size and initial moisture content on soil water diffusivity, D(θ), and unsaturated hydraulic conductivity, K(θ), horizontal absorption experiments were conducted on samples of loamy sand, sandy loam and clay–loam soils as well as on artificially prepared water-stable aggregates of a clay–loam sample (sizes 0.·25–0–25, 0·25–0·5, 0·5–1, 1–2, and 2–4 mm). For comparable moisture contents, D(θ) followed the order loamy sand > sandy loam > clay–loam. The effect of initial moisture content on D(θ) varied with soil texture. K(θ), which was evaluated using D(θ) for air-dry initial moisture content and the slopes of the water retention curves, also varied with soil texture.The D(θ) function for air-dry initial moisture content increased with the decrease in aggregate size, the increase being more pronounced below a size of 1 mm. Values of D(θ) obtained from initially airdry soil and at 10% of saturation moisture content did not differ greatly from one another. The K(θ) function was almost the same for aggregate sizes 1–2 and 2–4 mm. In the size ranges of < 1 mm, K(θ) increased with the decrease in aggregate size. The particle/aggregate size range of 0·1–0·5 mm was the most conducive to unsaturated water flow.

scholarly journals Vulnerability of soil aggregates in relation to soil properties

2011 ◽  
Vol 48 (No. 8) ◽  
pp. 329-334
Author(s):  
L. Borůvka ◽  
M. Valla ◽  
H. Donátová ◽  
K. Němeček
Keyword(s):  
Soil Properties ◽  
Soil Structure ◽  
Soil Aggregates ◽  
Aggregate Size ◽  
Fine Sand ◽  
Mechanical Forces ◽  
Soil Characteristic ◽  
Fine Silt ◽  
Wetting And Drying ◽  
Humus Quality

Stability of soil structure represents an indicator of soil quality. The aim of this paper was to assess the effect of soil properties on structure vulnerability in an Orthic Luvisol. The aggregates were most vulnerable to fast wetting (mean K<sub>v1</sub>&nbsp;= 9.99, i.e. this effect can decrease the aggregate size 9.99 times). Lower destruction was caused by slow wetting and drying (K<sub>v2</sub>&nbsp;= 3.70) and mechanical forces (K<sub>v3</sub>&nbsp;= 1.67). Fine silt (particles of 0.002&ndash;0.01 mm) was the most important soil characteristic decreasing aggregate vulnerability (r = &ndash;0.334, &ndash;0.248, and &ndash;0.393 for K<sub>v1</sub>, K<sub>v2</sub>, and K<sub>v3</sub>, respectively). Silt (0.01&ndash;0.05 mm) increased vulnerability to fast wetting (r = 0.318). Very fine sand (0.05&ndash;0.1 mm) increased vulnerability to mechanical impacts (r = 0.307). Organic carbon decreased vulnerability only slightly. Humus quality was rather related to porosity. Higher moisture of samples in time of collection increased aggregate vulnerability. Multiple regression, used for description of the effect of basic soil properties, provided the best model for K<sub>v1</sub>&nbsp;(R<sup>2</sup>&nbsp;= 27.45%), the poorest for K<sub>v2</sub>&nbsp;(R<sup>2</sup>&nbsp;= 7.23%).

scholarly journals Time rate of swelling of compacted highly plastic clay soil from Sudan

2018 ◽  
Vol 149 ◽  
pp. 02032 ◽  
Author(s):  
A M Elsharief ◽  
Mai Sufian
Keyword(s):  
Moisture Content ◽  
Clay Soil ◽  
Initial Moisture Content ◽  
Hyperbolic Model ◽  
Dry Density ◽  
Expansive Clay ◽  
Time Intervals ◽  
One Dimensional ◽  
Swell Percent ◽  
Three Stages

This paper investigates the development of swelling with time for a highly plastic and potentially expansive clay from Sudan. Soil samples were prepared in the laboratory at different moisture content values. The prepared samples were placed in the oedometer ring at three density levels and then placed in an oedometer cell which allows one dimensional swelling. Swelling was observed at different time intervals to 48 hours. The data was analyzed to determine the development of swelling with time. The data analysis clearly demonstrated three stages of swelling, initial, preliminary and secondary for all tested samples except the quasi-saturated ones. The swell percent and primary swelling were very sensitive to the initial moisture content and dry density of the tested samples. Most of the swelling took place during the first 24 hours for all the tested specimens. The hyperbolic model was assessed for prediction of the percent swell. The 12 hours data was found to be very successful in predicting the percentage swell.

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