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%).

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.

Soil structural development in a rehabilitated open-cast mine site in south-east Australia

2021 ◽  
Author(s):  
Tiia Haberstok ◽  
Evelin Pihlap ◽  
Franziska Bucka ◽  
Tabea Klör ◽  
Thomas Baumgartl ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Properties ◽  
Bulk Density ◽  
Soil Structure ◽  
Aggregate Size ◽  
Size Class ◽  
Mine Site ◽  
Open Cast Mine ◽  
Open Cast

&lt;p&gt;Rehabilitated soils from post mining fields are considered to have poor soil structure, low nutrient content and microbial activity. Soil development during rehabilitation is a complex biogeochemical process influenced by the inherent properties of the substrate used for the rehabilitation. Besides disturbed soil properties, in Australia soil rehabilitation success is also influenced by climatic conditions like high evaporation rate which affects rebuilding of soil system functions. There are several studies looking into the development of soil properties post rehabilitation in temperate climates, however, the intertwined development of soil structure, quality and quantity of soil organic matter (SOM) after the rehabilitation under water stressed environment is not clear until now.&lt;/p&gt;&lt;p&gt;In this study, we used a space-for-time chronosequence approach in the rehabilitated open-cast mine site at Yallourn (Victoria, Australia) to elucidate the development of soil structure and soil organic matter after rehabilitation. We selected five different fields with increasing rehabilitation ages (2, 3, 10, 21 and 39 years) and two mature soils that are used as grazing land. In each field, we sampled 6 independent locations with stainless steel cylinders (100 cm&lt;sup&gt;3&lt;/sup&gt;) at two depths of 0-4 cm and 10-14 cm. &amp;#160;All samples were analysed for bulk density, organic carbon (OC) and total nitrogen (TN) concentration. Selected samples were wet sieved into four aggregate size classes of &lt;63 &amp;#181;m, 63-200 &amp;#181;m, 200-630 &amp;#181;m and &gt;630 &amp;#181;m. Each aggregate size class was characterized by OC and TN concentration. The chemical composition of the SOM of selected samples was characterized using solid-state &lt;sup&gt;13&lt;/sup&gt;C NMR spectroscopy.&lt;/p&gt;&lt;p&gt;The studied soils have a strong temporal dynamic and variability as determined for the soil properties bulk density and SOM stocks. Aggregate fractionation showed that large macroaggregates (&gt;630 &amp;#181;m) were the most abundant size class fractions in each rehabilitation field, representing 95-75% of the total soil mass. SOM played an important role in the formation of large macroaggregates, where the highest contribution to total OC content was observed. It became evident that plant derived carbon had a decisive role in the structural formation, because O/N-alkyl-C and alkyl-C chemical shift regions represented the highest relative intensities throughout the chronosequence.&lt;/p&gt;

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

scholarly journals Total mercury distribution among soil aggregate size fractions in a temperate forest podzol

2018 ◽  
Vol 8 ◽  
Author(s):  
Antía Gómez Armesto ◽  
Lucía Bibián-Núñez ◽  
Claudia Campillo-Cora ◽  
Xabier Pontevedra-Pombal ◽  
Manuel Arias-Estévez ◽  
...  
Keyword(s):  
Temperate Forest ◽  
Aggregate Size ◽  
Fine Sand ◽  
Soil Aggregate ◽  
Coarse Sand ◽  
Coarse Silt ◽  
Fine Silt ◽  
Size Fractions ◽  
Total Hg ◽  
Sand Size

This study determined the distribution of total Hg (Hg<sub>T</sub>) among aggregate size fractions in the A, E, Bh and Bs horizons of a representative temperate forest podzol. The aggregate distribution was dominated by the coarse sand size fraction (average of 55%) followed by fine sand (29%), fine silt (10%), coarse silt (4%) and clay (2%). In general, Hg<sub>T</sub> mean values increased as the aggregate size become smaller: clay (170 ng g<sup>-1</sup>) &gt; fine silt (130 ng g<sup>-1</sup>) &gt; coarse silt (80 ng g<sup>-1</sup>) &gt; fine sand (32 ng g<sup>-1</sup>) &gt; coarse sand (14 ng g<sup>-1</sup>). Total Hg enrichment in clay-sized aggregates ranged from 2 to 11 times higher than the values shown by the bulk soil (&lt; 2 mm). The accumulation of Hg<sub>T</sub> in the finer size aggregates was closely related to total organic C, Na-pyrophosphate extracted C, metal (Al, Fe)-humus complexes and Al and Fe oxyhydroxides. Indeed, these parameters varied significantly (<em>p </em>&lt; 0.05) with the aggregate size and their highest values were found in the finer fractions. This suggested the role of these soil compounds in the increase of the specific surface area per mass unit and negative charges in the smallest aggregates, favouring Hg retention. Mercury accumulation factor (Hg<sub>AF</sub>) values reached up to 10.8 in the clay size aggregates, being close to 1 in sand size fractions. Regarding Hg enrichment factors (Hg<sub>EF</sub>), they were &lt; 4 (“moderate pollution” category) in most of the horizons and aggregate sizes. Grain size mass loading (GSF<sub>Hg</sub>) revealed that finer fractions had a higher Hg loading than their mass fractions, with a notable contribution of fine silt which made up &gt; 50% of Hg<sub>T</sub> in Bh and Bs horizons. The potential ecological risk index (PERI<sub>Hg</sub>) increased as the aggregate size decreased, with the highest values in the illuvial horizons (45-903) and lowest in the E horizon (3-363). Heterogeneous distribution of Hg in the soil aggregate size fractions must be considered for Hg determination for purposes such as critical loads, background values or environmental risk indices. In addition, Hg accumulation in finer aggregates could be of concern due to its potential mobility in forest soils, either transferred by leaching to groundwater and freshwaters or mobilized by runoff in surface horizons.

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.

Descriptors for soil development in a water limited environment of a rehabilitated open-cast mine site in south-east Australia

2020 ◽  
Author(s):  
Evelin Pihlap ◽  
Franziska Bucka ◽  
Tiia Haberstok ◽  
Emily Scholes ◽  
Tabea Klör ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Properties ◽  
Bulk Density ◽  
Microbial Activity ◽  
Soil Structure ◽  
Aggregate Size ◽  
Water Infiltration ◽  
Soil System ◽  
Open Cast

&lt;p&gt;Soil structure and soil organic matter (SOM) are closely linked characteristics describing the status of development of a soil. Their interactions affect various physical, chemical and biological soil properties and functions like water holding capacity, water infiltration, composition of the carbon pool and microbial activity. Rehabilitated soils from post mining fields are considered to have poor soil structure, low nutrient content and microbial activity. Besides disturbed soil properties, in Australia soil rehabilitation success is also influenced by climatic conditions like high evaporation rate which affects rebuilding of soil system functions. Although there are several studies looking into the development of soil properties post rehabilitation in temperate climates, the intertwined development of soil structure and quality and quantity of SOM during soil formation under water stressed environment is not clear until now.&lt;/p&gt;&lt;p&gt;In this study we used a space-for-time chronosequence approach in the rehabilitated open-cast mines at Yallourn Mine (Victoria, Australia) to elucidate the development of soil structure and soil organic matter after rehabilitation in a water limited environment. We selected five different fields with different rehabilitation ages (40, 22, 11, 4 and 3 years) and two mature soils that are used as grazing land. In each field we sampled 6 independent locations with stainless steel cylinders (100 cm&lt;sup&gt;3&lt;/sup&gt;) at two depths of 0-4 cm and 10-14 cm. &amp;#160;All samples were analysed for bulk density, organic carbon (OC) and total nitrogen (TN) concentration. Selected samples were wet sieved into four aggregate size classes of &lt;63 &amp;#181;m, 63-200 &amp;#181;m, 200-630 &amp;#181;m and &gt;630 &amp;#181;m. For detecting OC contribution to aggregate formation, OC and TN was measured from each aggregate size fraction. This system is temporarily highly dynamic and shows different developments for bulk density and SOM stocks, which had an effect on the structure of the microbial communities. Along the space-for-time chronosequence we can observe soil structure formation with ageing and a build-up of a OM, which has a positive effect on recovering soil functionality.&lt;/p&gt;

scholarly journals Soil consistency as a factor determining the soil structure of clay soils.

1956 ◽  
Vol 4 (1) ◽  
pp. 122-125 ◽  
Author(s):  
P. Boekel ◽  
P.L. Peerlkamp
Keyword(s):  
Soil Structure ◽  
Soil Aggregates ◽  
Field Capacity ◽  
Clay Soils ◽  
Mechanical Forces ◽  
Plastic Limit ◽  
Top Soil ◽  
Moisture Percentage ◽  
Soil Conditioners ◽  
Plastic Transformation

The deterioration of the aggregation of several Dutch clay soils during the period after plowing seems to be caused by a plastic transformation of the soil aggregates under the influence of mechanical forces, even very weak ones such as the weight of the top soil. It depends on the consistency and moisture characteristics of the soil, the drainage of the top soil, etc. The location of the point pF 1.9 ("field capacity") on the moisture percentage scale with regard to the upper plastic limit, the sticky point and the lower plastic limit appears to be a better index for the structure of clay soils than figures obtained from a wet-sieving analysis, and some results of experiments on the effects of lime, gypsum and soil conditioners on soil structure illustrate this.-From authors' summary. (Abstract retrieved from CAB Abstracts by CABI’s permission)

SORPTION OF CARBON AND PHOSPHORUS FROM LIQUID POULTRY MANURE BY SOIL AGGREGATES OF DIFFERING SIZE

1985 ◽  
Vol 65 (3) ◽  
pp. 467-473 ◽  
Author(s):  
V. K. BHATNAGAR ◽  
M. H. MILLER
Keyword(s):  
Soil Aggregates ◽  
Poultry Manure ◽  
Aggregate Size ◽  
Liquid Manure ◽  
Inorganic P ◽  
Supernatant Liquid ◽  
Extractable P ◽  
P Content ◽  
Manure Slurry ◽  
Total P

A series of laboratory experiments was conducted to determine the mechanism(s) responsible for a previously reported observation that addition of liquid manure to soil increased the NaHCO3-extractable P (Ext-P) of large aggregates (> 2 mm) more than that of smaller aggregates whereas addition of an inorganic P solution did not. Application of liquid poultry manure increased the total P, Ext-P and total C concentrations in large aggregates (> 2 mm) much more (> 2.5 ×) than that in small aggregates (< 1 mm). Addition of inorganic P solution or of supernatant liquid from a centrifuged manure slurry increased the P content of the large aggregates only slightly (1.2 ×). A greater increase in Ext-P in large aggregates was observed even when the smaller aggregates were purposely layered on top of the larger ones prior to addition of the liquid manure. A similar but less pronounced effect of aggregate size on increase in P or C concentration was observed when different sized aggregates were left in contact with an effectively infinite source of liquid manure for 24 h. It is concluded that the larger aggregates absorbed more of the bulk manure slurry than smaller aggregates. A partial sealing of small aggregates by particulates is suggested as a possible mechanism. Key words: Carbon, phosphorus, liquid manure, soil aggregates

A numerical study on the influences of underlying soil and backfill characteristics on the dynamic behaviour of typical integral bridges

Bauingenieur ◽  
2020 ◽  
Vol 95 (11) ◽  
pp. S 2-S 11
Author(s):  
H. D. B. Aji ◽  
M. B. Basnet ◽  
Frank Wuttke
Keyword(s):  
Soil Structure ◽  
Dynamic Behaviour ◽  
Numerical Study ◽  
Coupled System ◽  
Soil Structure Interaction ◽  
Dynamic Resistance ◽  
Soil Characteristic ◽  
Structure Interaction ◽  
Integral Bridges ◽  
Underlying Soil

Abstract The identification of the dynamic behaviour of a structure is one of the crucial steps in the design of the dynamic resistance of the structure. The dynamic behaviour is represented by the natural frequencies and damping which are subsequently used along with the considered dynamic actions in the design process. In regard of integral bridge concept, one of the consequences of the omission of joints and bearings is the substantial soil-structure interaction which in turn increases the sensitivity of the dynamic behaviour of the bridges to the surrounding soil characteristic. In this article, we extended our hybrid BEM-FEM steady-state dynamic numerical tool to the 3D regime, developed by utilizing an in-house BEM and the commercial FEM software ABAQUS and use it to analyse the dynamic interaction between the bridge and the underlying soil as well as the backfill. The numerical results from four typical integral bridges show that underlying soil characteristic has great effect on the resonant frequencies and the damping. The backfill material properties tend to have less significant role due to the abutment wingwalls dominating the force transfer between the soil and the superstructure. The results also show that the degree of influence of the soil-structure interaction on the coupled system is affected by the type of load pattern in addition to the flexural stiffness of the superstructure.

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