Evaluation of soil structure by using computer-assisted tomography

Soil Research ◽  
1989 ◽  
Vol 27 (2) ◽  
pp. 313 ◽  
Author(s):  
VK Phogat ◽  
LAG Aylmore
Keyword(s):  
Spatial Distribution ◽  
Bulk Density ◽  
Gamma Ray ◽  
Glass Tube ◽  
Total Porosity ◽  
Soil Samples ◽  
Computer Assisted ◽  
Wetting And Drying ◽  
Attenuation Coefficients ◽  
Computer Assisted Tomography

Computer assisted tomography applied to gamma ray attenuation (CAT scanning) has been evaluated as a method for directly measuring the spatial distribution of soil macroporosity and for monitoring changes which occur during wetting and drying processes, in a non-destructive manner. Total porosity calculated from the bulk density of soil and glass tube samples varying in bulk density from 0.759 to 1.602 g cm-3 correlated well with total porosity calculated from CAT scan data. The system was able to detect changes in bulk density for a loam soil of the order of 16 mg cm-3, and objects of 2.0 by 2.0 mm dimensions could be pictorially resolved in the scanning plane. Statistically, the system resolves pixels differing by at least 6.14% in attenuation coefficient value from surrounding pixels. Average macroporosity and the spatial and frequency distribution of macroporosity for soil samples were determined by assigning the value of zero macroporosity to pixels having gamma attenuation coefficients corresponding to the bulk density of a soil aggregate, 100% macroporosity to pixels with zero attenuation coefficients and proportional values to pixels with intermediate coefficients. The CAT scanning of soil samples before and after a wetting and drying cycle illustrated the greater reduction in macroporosity for soil wetted under flooding compared with that wetted under capillary action. The CAT scanning clearly has considerable potential for studying the spatial distribution of soil macrostructure and for monitoring the changes in macroporosity which occur during wetting and drying processes in soil columns.

Computation of hydraulic conductivity of porous materials using computer-assisted tomography

Soil Research ◽  
1996 ◽  
Vol 34 (5) ◽  
pp. 671 ◽  
Author(s):  
VK Phogat ◽  
LAG Aylmore
Keyword(s):  
Spatial Distribution ◽  
Hydraulic Conductivity ◽  
Glass Bead ◽  
Gamma Ray ◽  
Pore Space ◽  
Empirical Relationship ◽  
Soil Aggregate ◽  
Computer Assisted ◽  
Computer Assisted Tomography ◽  
Gamma Ray Attenuation

The spatial distribution of porosity and continuity of pore space in glass bead and soil aggregate systems has been characterised by application of computer-assisted tomography to gamma-ray attenuation measurements. It has been demonstrated that a useful empirical relationship between hydraulic conductivity and pore size and continuity for the glass bead system as measured by CAT scanning can be derived.

Soil bulk density evaluation by conventional and nuclear methods

Soil Research ◽  
2005 ◽  
Vol 43 (1) ◽  
pp. 97 ◽  
Author(s):  
L. C. Timm ◽  
L. F. Pires ◽  
K. Reichardt ◽  
R. Roveratti ◽  
J. C. M. Oliveira ◽  
...  
Keyword(s):  
Bulk Density ◽  
Gamma Ray ◽  
Soil Bulk Density ◽  
Soil Samples ◽  
Soil Science ◽  
Tukey Test ◽  
Nuclear Methods ◽  
Density Values ◽  
Density Evaluation ◽  
Gamma Ray Computed Tomography

Among the methods used to measure soil bulk density, the following have been prominent: paraffin sealed clod (PS), volumetric ring (VR), and the modern methods like gamma ray computed tomography (GCT) and the neutron/gamma surface gauge (SG). The objective of this work was to compare soil bulk density values obtained through these methods, with the aim of assisting researchers on the choice of the more appropriate method. For this, a 200-m spatial transect was chosen in an experimental area cultivated with coffee, belonging to ESALQ/USP, Piracicaba, SP, Brazil. The SG readings were first taken in the field and thereafter soil samples were collected at 8 different points, spaced at 25 m, for the other methods. The lowest values of soil bulk density were obtained for the SG method (average 1.468 g/cm3) and the highest for the PS (average 1.685 g/cm3), which was similar to the GCT method (average 1.684 g/cm3). The average soil bulk density for the VR method, which has been used in soil science as a standard method, was 1.544 g/cm3. The Tukey test indicates that the PS and GCT methods do not differ significantly (P > 0.05). They do differ in comparison with VR and SG, which also do not differ among themselves.

scholarly journals Spatial Variability of Saturated Hydraulic Conductivity and its Links with other Soil Properties at the Commune Scale

2021 ◽  
Author(s):  
Boguslaw Usowicz ◽  
Jerzy Lipiec
Keyword(s):  
Spatial Distribution ◽  
Hydraulic Conductivity ◽  
Organic Carbon ◽  
Spatial Variability ◽  
Soil Properties ◽  
Bulk Density ◽  
Soil Water ◽  
Total Porosity ◽  
The Other ◽  
The Mean

Abstract Saturated hydraulic conductivity (SHC) is a key property for evaluating soil water movement and quality. Most studies on spatial variability of SHC have been performed soil at a field or smaller scale. Therefore, the aim of this work was to assess (quantify) the spatial distribution of SHC at the commune scale and its relationship with other soil properties, including intrinsic sand, silt, and clay contents, relatively stable organic carbon, cation exchange capacity (CEC), dynamic water content (WC), total porosity (FI), and dry bulk density (BD) in the surface layer (0–20 cm). The spatial relationships were assessed using a semivariogram and a cross-semivariogram. The studied commune (140 km2) with predominantly permeable sandy soils with low fertility and productivity is located in the south-eastern part of Poland (Podlasie region). The mean sand and organic carbon contents are 74 andobablyctknąć, czy o to chodzid mniej znacznie mniejszed? ? 0.86 and their ranges (in %) are 45-95 and 0.002-3.75, respectively. The number of individual samples varied from 216–228 (for SHC, WC, BD, FI) to 691 for the other soil properties. The best fitting models were adjusted to the empirical semivariogram (exponential) and the cross-semivariogram (exponential, Gaussian, or linear) used to draw maps with kriging. The results showed that, among the soil properties studied, SHC was most variable (coefficient of variation 77.3%) and significantly (p <0.05) positively correlated with total porosity (r = 0.300) and negatively correlated with soil bulk density (r = –0.283). The mean SHC was 2.597 m day–1 and ranged from 0.01 up to 11.54 m day–1. The spatial autocorrelation (range) of SHC in the single (direct) semivariograms was 0.081° (8.1 km), while it favourably increased up to 0.149–0.81° (14.9–81 km) in the cross-semivariograms using the OC contents, textural fractions, and CEC as auxiliary variables. The generated spatial maps allowed outlining two sub-areas with predominantly high SHC above 3.0 m day–1 in the northern sandier (sand content >74%) and less silty (silt content <22%) part and, with lower SHC in the southern part of the commune. Generally, the spatial distribution of the SHC values in the commune area depended on the share of individual intrinsic textural fractions. On the other hand, the ranges of the spatial relationship between SHC and the intrinsic and relatively stable soil properties were much larger (from ~15 to 81 km) than between SHC and the dynamic soil properties (0.3-0.9 km). This knowledge is supportive for making decisions related to land management aimed at reduction of hydraulic conductivity and chemical leaching and improvement of soil water resources and crop productivity.

scholarly journals Laboratory Investigation of Pipeline/Soil Interactions Using X-Ray Computer Assisted Tomography

1996 ◽  
Author(s):  
Apostolos Kantzas ◽  
Allan Trigg
Keyword(s):  
Bulk Density ◽  
Cross Sections ◽  
Ct Scanning ◽  
Computer Assisted ◽  
Calibration Data ◽  
Porous Rocks ◽  
X Ray ◽  
Variable Diameter ◽  
Computer Assisted Tomography ◽  
Materials Used

X-ray Computer Assisted Tomography (CAT or CT) Scanning has been used successfully for the determination of physical properties of porous rocks and for flow visualization in a variety of porous media including soils. CAT scanning has also been demonstrated as an effective tool for the visualization of different stress conditions in porous rocks with greater accuracy when dealing with unconsolidated media. This success was the motivation in trying to expand the diagnostic capabilities of CAT scanning in the phenomena associated with pipeline / soil interactions. For this purpose, a physical model was built. The model consisted of a x-ray transparent holder which had two pistons, one at each end. The pistons were mounted on a cylindrical rod of variable diameter. The holder was then filled with sand. The entire apparatus was placed in the CAT scanner gantry. A series of experiments were performed whereby the rod was forced through the sand pack. The holder was scanned from end to end and the images of various cross-sections were acquired and analyzed for bulk density and porosity. The experiments were coupled with calibration experiments where a uniformly packed sand was loaded under hydrostatic load in given increments. As the sand pack compacted, its bulk density increased. The normalized change in density (strain) was monitored as a function of the pressure load (stress). The results of the calibration tests were used to identify the levels of stress on the sand surrounding the moving rod. It was discovered that areas of compaction ahead of the moving rod and dilation behind the moving rod could be successfully identified and mapped. The stress / strain calibration data allowed the translation of the bulk density images into stress maps around the pipeline. Although the system and materials used in this work were utilized only for demonstration, it was evident that this type of experimental work could be successfully used to calibrate complicated field scale computer models that are very difficult to tune because of the lack of experimental data.

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