Development of Mechanical Soil Stability In An Initial Homogeneous Loam And Sand Under In-Situ Field Conditions

2021 ◽  
Author(s):  
Ulla Rosskopf ◽  
Daniel UTEAU ◽  
Stephan PETH
Keyword(s):  
Soil Structure ◽  
Mechanical Energy ◽  
Soil Stability ◽  
Compression Tests ◽  
Undisturbed Soil ◽  
Initial Development ◽  
Short Period ◽  
Influence Of Substrate ◽  
Undisturbed Soil Cores

Abstract PurposeSoil structure evolving from physical and biological processes is closely related to soil mechanical characteristics and texture. A soil plot experiment in Bad Lauchstädt, Germany, allowed us to study the influence of substrate and genotype on the initial development of mechanical traits, differences between depths, and changes over the course of two years. MethodsPlots were homogeneously filled with a loam and a sand and planted with two maize (Zea mays L.) genotypes (wild type (WT) and rth3 mutant) with contrasting root hair attributes. Undisturbed soil cores were taken in 2019 and 2020 at 14 and 34 cm depth. Confined uniaxial compression tests were performed to determine pre-compression stress (σpc), compressibility (Cc, Cs) and elasticity index (EI). Mechanical energy was calculated based on penetration resistance tests with a penetrometer needle resembling root geometries. Resultsσpc, Cc and Cs were significantly higher in loam as compared to sand, whereas the factor genotype proved to be negligible. Over time, σpc increased and Cc decreased in loam from 2019 to 2020 and Cs declined in both substrates. Higher mechanical energies were observed in loam and partially in WT. Required energy was higher at 14 cm than at 34 cm depth and decreased from 2019 to 2020 in sand. Airdry sand samples required four times as much energy than those at -50 kPa.ConclusionFor the development of the mechanical traits examined texture proved to be the dominating factor and changes in soil stability could be observed within a short period of time.

SOIL MORPHOLOGY AND SOIL PHYSICAL PROPERTIES. I. SOIL AERATION

1972 ◽  
Vol 52 (3) ◽  
pp. 311-321 ◽  
Author(s):  
K. W. AYRES ◽  
R. G. BUTTON ◽  
E. DE JONG
Keyword(s):  
Soil Structure ◽  
Regression Coefficient ◽  
The Other ◽  
Soil Morphology ◽  
Soil Horizons ◽  
Undisturbed Soil ◽  
Soil Aeration ◽  
Structural Types ◽  
Highly Correlated ◽  
Undisturbed Soil Cores

The relation between soil structure and soil aeration was investigated on undisturbed soil cores from soil horizons exhibiting six distinct kinds of soil structure (prismatic, columnar, blocky, granular, platy, massive) over a broad range of soil texture. Soil aeration was characterized at ⅓ atm suction by measurements of air porosity, relative diffusivity (D/Do) and the rate of oxygen diffusion to a platinum microelectrode (ODR). Aeration was adequate in most of the Chernozemic soil horizons studied; however, aeration in many of the Bnt horizons of the Solonetzic soils was inadequate. Air porosity and D/Do were highly correlated. The regression coefficient for D/Do vs. air porosity for blocky structures was significantly different from that found for the other five structural types. For granular structures a negative correlation was found for ODR vs. air porosity compared with a low positive correlation found for the other structure types.

scholarly journals Shrinkage Characteristics of Boulder Marl as Sustainable Mineral Liner Material for Landfill Capping Systems

2018 ◽  
Vol 10 (11) ◽  
pp. 4025 ◽  
Author(s):  
Steffen Beck-Broichsitter ◽  
Horst Gerke ◽  
Rainer Horn
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Shrinkage Stress ◽  
Undisturbed Soil ◽  
Liner Material ◽  
Size Dependent ◽  
Undisturbed Soil Cores ◽  
Shrinkage Behavior

The soil shrinkage behavior of mineral substrates needs to be considered for engineering long-term durable mineral liners of landfill capping systems. For this purpose, a novel three-dimensional laser scanning device was coupled with (a) a mathematical-empirical model and (b) in-situ tensiometer measurements as a combined approach to simultaneously determine the shrinkage behavior of a boulder marl, installed as top and bottom liner material at the Rastorf landfill (Northern Germany). The shrinkage behavior, intensity, and geometry were determined during a drying experiment with undisturbed soil cores (100 cm3) from two soil pits; the actual in-situ shrinkage was also determined in 0.2, 0.5, 0.8, and 1.0 m depth by pressure transducer tensiometer measurements during a four-year period. The volume shrinkage index was used to describe the pore size dependent shrinkage tendency and it was classified as low (4.9%) for the bottom liner. The in-situ matric potentials in the bottom liner ranged between −100 and −150 hPa, even during drier periods, thus, the previously highest observed drying range (pre-shrinkage stress) with values below −500 hPa and −1000 hPa was not exceeded. Therefore, the hydraulic stability of the bottom liner was given.

Carbon kinetics in a Black Chernozem with roots in situ

1995 ◽  
Vol 75 (3) ◽  
pp. 299-305 ◽  
Author(s):  
J. G. Xu ◽  
N. G. Juma
Keyword(s):  
Decomposition Rate ◽  
Microbial Respiration ◽  
Root Decomposition ◽  
Soil Cores ◽  
Undisturbed Soil ◽  
Barley Cultivars ◽  
The Difference ◽  
Kinetics Of ◽  
Undisturbed Soil Cores

The rates of decomposition of roots and root-derived materials are needed to assess the contribution of these materials to sequestration of organic carbon in soil. The objective of this study was to examine the kinetics of different forms of C in a Black Chernozem, with roots in situ under two barley cultivars, using 14C pulse-labeling and incubation methods. Plants were pulse-labeled (1 d) with 14CO2 25 d after emergence. Shoots were excised, and undisturbed soil cores containing the roots of a single plant were incubated at 20 °C for 80 d. The experiment involved two barley cultivars, with six replications at six sampling dates (days 0, 5, 10, 25, 40 and 80). The percentage of the labile components in roots of Abee (48%) was greater than that of Samson (39%), but the half lives of the labile components (0.693 k−1) of the roots were not significantly different between the two barley cultivars. The decomposition-rate constants for the resistant components of the roots were also not significantly different between the two barley cultivars. This indicated that the difference between the two barley cultivars in root decomposition rate could be explained by the difference in the ratios of the labile components to the resistant components. The average half life of 14C in roots was 41 d for Abee and 71 d for Samson. The amount of root 14C + soil 14C under Samson was higher than under Abee during the incubation period. These results supported our hypothesis that the cultivar that translocated more 14C-labeled carbon into roots and root-derived material has greater microbial respiration and greater C stabilization because a portion of added C remains in the soil after being transformed by microorganisms. Key words: Carbon kinetics, carbon sequestration, roots in situ, 14C pulse-labeling, Black Chernozem

scholarly journals Approaches to calibrate in-situ capacitance soil moisture sensors and some of their implications

2016 ◽  
Author(s):  
N. A. L. Archer ◽  
B. R. Rawlins ◽  
B. P. Machant ◽  
J. D. Mackay ◽  
P. I. Meldrum
Keyword(s):  
Soil Moisture ◽  
Field Measurements ◽  
Soil Cores ◽  
Undisturbed Soil ◽  
Soil Moisture Sensors ◽  
Soil Sensors ◽  
Laboratory Calibration ◽  
Rain Events ◽  
Undisturbed Soil Cores

Abstract. Capacitance probes are increasingly being used to monitor volumetric water content (VWC) in field conditions and are provided with in-built factory calibrations so they can be deployed at a field site without the requirement for local calibration. These calibrations may not always have acceptable accuracy and therefore to improve the accuracy of such calibrations soil-specific laboratory or field calibrations are required. In some cases, manufacturers suggest calibration is undertaken on soil in which the structure has been removed (through sieving or grinding), whilst in other cases manufacturers suggest structure may be retained. The objectives of this investigation were to (i) demonstrate the differences in laboratory calibration of the sensors using both structured and unstructured soils, (ii) compare moisture contents at a range of suctions with those predicted from soil moisture release curves for their texture classes (iii) compare the magnitude of errors for field measurements of soil moisture based on the original factory calibrations and the laboratory-based calibrations using structured soil. Grinding and sieving clay soils to  50 % water to the ground and sieved soil samples, dielectric values to VWC > 50 % were observed to be significantly lower than using undisturbed soil cores taken from the field and therefore undisturbed soil cores were considered to be better to calibrate capacitance probes. Generic factory calibrations for most soil sensors have a range of measurement from 0 to 50 %, which is not appropriate for the studied clay-rich soil, where ponding can occur during persistent rain events, which are common in temperate regions.

Helical piles in unsaturated structured soil: a case study

2016 ◽  
Vol 53 (1) ◽  
pp. 103-117 ◽  
Author(s):  
Cristina de Hollanda Cavalcanti Tsuha ◽  
João Manoel Sampaio Mathias dos Santos Filho ◽  
Thiago da Costa Santos
Keyword(s):  
Soil Structure ◽  
Load Test ◽  
Bottom Plate ◽  
Natural Soil ◽  
Residual Soil ◽  
Compression Tests ◽  
Undisturbed Soil ◽  
Cone Penetration Tests ◽  
Helical Piles ◽  
Load Tests

The use of helical piles as tower foundations in Brazil has increased considerably during the last 5 years. A number of these piles are installed in unsaturated structured soils that cover a significant part of the Brazilian territory. However, the installation of helical piles in such soils produces a breakdown of the natural soil structure, which affects the pile performance for tension applications. This scenario motivates the present work, in which a comprehensive pile load-test program was carried out on helical piles composed of a single helix or multi-helices, installed in an unsaturated tropical residual soil. Eleven full-scale pile axial load tests were carried out, including two compression and nine tension tests. In addition, cone penetration tests were performed close to the piles after installation, and undisturbed soil samples were collected at the depth of the helices. The aim of these additional tests was to contribute to the understanding of the effect of helical pile installation on soil structure. The results of the tension load tests showed that the changes in the structure of the porous tested soil result in particularly low pile uplift capacities. In contrast, the load–settlement curves of the pile compression tests indicate a peculiar failure mechanism due to the sensitive soil structure associated with the high void ratio of the intact soil beneath the bottom plate.

Passive acoustic emissions: a dynamic tool to monitor soil structure variations?

2021 ◽  
Author(s):  
Marine Lacoste ◽  
Guillaume Giot ◽  
Maud Seger ◽  
Isabelle Cousin
Keyword(s):  
Surface Density ◽  
Soil Structure ◽  
Acoustic Emissions ◽  
Soil Surface ◽  
Agricultural Field ◽  
Undisturbed Soil ◽  
Soil Desiccation ◽  
Acoustic Signature ◽  
Two Samples

<p>The structure of soils, i.e. the macroscopic organization of aggregates and pores, conditions the storage and transport of water and gas in the soil, and strongly determines the physico-chemical environment of soil organisms (plants, micro and macro-organisms). The description of the soils structure dynamics constitutes a major issue in the current context of global change, at the scientific, environmental and agronomic level. However, few tools are available to monitor this dynamic non-destructively and in situ. We therefore propose to develop a new method based on the analysis of acoustic emissions (AE) spontaneously emitted by soils during the evolution of their structure. A laboratory feasibility study was conducted to explore the links between variations in soil structure and the AE emitted during soil desiccation.</p><p>Two undisturbed soil columns (8 cm in diameter, 5 cm high) were sampled in an agricultural field (near Chartres in France), in the surface horizon of a Glossic Retisol. These cylinders were air dried (20°C during 9 days), and the AE produced during drying were monitored using piezoelectric sensors place at the soil surface. The concomitant soil structure changes were followed through 3D images, acquired by X-ray tomography (CIRE platform, INRAE, Nouzilly) all along the experiment. These images, with a resolution of 168 µm, were used to characterize the pore network (porosity, surface density, connectivity, etc.).</p><p>The dynamics of the EAs recorded during the drying of the samples is comparable for the two samples: the AE rates are maximum at the start of the experiment and then reach a plateau. Changes in soil structure follow the same dynamics, e.g. considering porosity or surface density of the pores. If we analyze the relationship between the signals recorded by the surface sensors (EA rate) and the porosity, we observe a linear relationship (R² of 0.79). This relationship, although encouraging, remains to be consolidated by additional results.</p><p>To go further, it is also necessary to define the necessary conditions to perform such a measurement in situ, and to improve the acoustic signal processing to characterize the EA produced during soil desiccation. Indeed, a major objective of our work is to differentiate, thanks to EAs, the various factors responsible for the evolution of soil structure (physical and biological), by determining their "acoustic signature".</p>

Some effects of cultivation and waterlogging on the availability of phosphorus in pasture soils

1965 ◽  
Vol 16 (3) ◽  
pp. 413 ◽  
Author(s):  
CH Williams ◽  
JR Simpson
Keyword(s):  
Soil Phosphorus ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Available Phosphorus ◽  
Undisturbed Soil ◽  
Short Period ◽  
Subsurface Soil ◽  
Waterlogging Treatment ◽  
Mixed Soils ◽  
Undisturbed Soil Cores

Compared with growth on undisturbed soil, uniform mixing of the surface 4 in. of pasture soils caused a decrease in the yield of subterranean clover grown in pot culture. This was shown to be due to lowered availability of the soil phosphorus and was probably brought about by sorption of the available phosphorus, which had accumulated at the soil surface, by the unsaturated subsurface soil. Short periods of waterlogging (1–2 days) also brought about lowered availability of soil phosphorus. This occurred both with undisturbed soil cores and with mixed soils, but was much more severe when the soil was mixed. The effect appeared to be due to the conversion of phosphate to non-available forms during the short period of anaerobic conditions. The phosphate sorption capacity of the soil was increased by the waterlogging treatment but decreased to its original value when the soil was air-dried.

scholarly journals Traffic effects on the soil preconsolidation pressure due to eucalyptus harvest operations

2005 ◽  
Vol 62 (3) ◽  
pp. 248-255 ◽  
Author(s):  
Moacir de Souza Dias Junior ◽  
Fernando Palha Leite ◽  
Edson Lasmar Júnior ◽  
Cezar Francisco Araújo Junior
Keyword(s):  
Soil Compaction ◽  
Soil Structure ◽  
Soil Samples ◽  
Compression Tests ◽  
Undisturbed Soil ◽  
Structure Degradation ◽  
Preconsolidation Pressure ◽  
Before And After ◽  
Two Stages ◽  
Wood Transport

One of the limitations for reaching sustainable forest development is related to the traffic of machines and vehicles during harvest operations and wood transport, which may cause soil structure degradation. Seeking a way to analyze this problem, the objective of this study was to determine the traffic effects due to harvest operations and wood transport, on the preconsolidation pressure (sigmap) in a Typic Acrustox cultivated with eucalyptus. This study was conducted using undisturbed soil samples collected at the 0.1-0.125 m depth. Undisturbed soil samples were used in the uniaxial compression tests. Soil sampling consisted of two stages, before and after the mechanized harvest operations. The traffic effects on the sigmap in the dry season indicated that the soil compaction process was neither evident nor important. However, in the rainy season the traffic effects on the sigmap indicated that the operations performed with Harvester and Forwarder caused greater soil compaction than those with Motorized Saw and Manual, which caused less soil compaction.

Isoproturon movement and dissipation in undisturbed soil cores from a grassed buffer strip

Agronomie ◽  
2000 ◽  
Vol 20 (3) ◽  
pp. 297-307 ◽  
Author(s):  
Pierre Benoit ◽  
Enrique Barriuso ◽  
Philippe Vidon ◽  
Benoit Réal
Keyword(s):  
Soil Cores ◽  
Undisturbed Soil ◽  
Buffer Strip ◽  
Undisturbed Soil Cores

scholarly journals Hot Workability of 300M Steel Investigated by In Situ and Ex Situ Compression Tests

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 880 ◽  
Author(s):  
Rongchuang Chen ◽  
Haifeng Xiao ◽  
Min Wang ◽  
Jianjun Li
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Hot Working ◽  
Ex Situ ◽  
Lower Strain Rate ◽  
Hot Workability ◽  
Compression Tests ◽  
300M Steel ◽  
Lower Strain

In this work, hot compression experiments of 300M steel were performed at 900–1150 °C and 0.01–10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

Sign in / Sign up

Export Citation Format

Share Document