Impacts of soil moisture content and vegetation on shear strength of unsaturated soil

AbstractAn assessment of long-term performance of low level waste-enclosing cement grouts requires diffusivity data for radionuclide species such as, 129I and 99Tc. The diffusivity of radionuclides in soil and concrete media was collected by conducting soil-soil and concrete-soil half-cell experiments. The soil diffusivity coefficients for iodide were 7.03 × 10−8 cm2/s and 2.42 × 10−7cm2/s for soils at 4% and 7% moisture contents, respectively. Iodide diffusivity in soil is a function of moisture content and is about an order of magnitude slower at lower moisture content. The soil diffusivity coefficients for 99Tc were 5.89±0.80 × 10−8 cm2/s (4% moisture content) and 2.04±0.57 × 10−7 cm2/s (7% moisture content), respectively. The soil diffusivity of iodide and 99Tc were similar in magnitude at both water contents, indicating that these ions have similar diffusion mechanisms in unsaturated coarse-textured Hanford soil. The diffusivity of iodide in concrete ranged from 2.07 × 10−14 cm2/s (4% soil moisture content) to 1.31 × 10−12 cm2/s (7% soil moisture content), indicating that under unsaturated soil moisture conditions, iodide diffusivity is highly sensitive to changing soil moisture conditions. Depending on the soil moisture content, the diffusivity of 99Tc in concrete ranged from 4.54 × 10−13 cm2/s to 8.02 × 10−12 cm2/s. At 4% soil moisture content, iodide diffused about 20 times more slowly than 99Tc, and at 7% soil moisture content, iodide in concrete diffused about 6 times slower than 99Tc.

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Soil conditions in the donga soils in subhumid zone in West Africa

Canadian Journal of Soil Science ◽

10.1139/cjss-2020-0137 ◽

2021 ◽

Author(s):

Julien AVAKOUDJO ◽

Félix Kouelo Alladassi ◽

Valentin Kindomihou ◽

Tobi Moriaque Akplo ◽

Mahugnon Socrate Agonvinon ◽

...

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Unsaturated Soil ◽

Soil Moisture Content ◽

Water Erosion ◽

Soil Conditions ◽

P Value ◽

Natural Habitats ◽

Moisture Estimation ◽

Soil Moisture Measurement

Water erosion threatens large areas around the world. Donga is one of the witness of Gully erosion in northern Benin which induces serious threats to the natural habitats. This study was conducted to evaluate soil moisture content in different donga type (microdongas, mesodongas and megadongas) and its variation at different topographic level. The thermogravimetric soil moisture measurement technique was used for moisture estimation on saturated and unsaturated soil. Data were analyzed through ANOVA-test and T-test with SAS software. The results showed that soil moisture content varied according to donga types. On unsaturated soil, higher difference (2.75%, p-value =0.0328) was obtained in mesodongas at the middle followed by megadongas at the middle (2.6%, p-value = 0.034). On saturated soil, higher difference was obtained in mesodongas at the upstream (6.51%, p-value <.0001) at downslope (4.55%, p-value = 0.0032) and in the middle (4.32%, p-value = 0.0328) followed by microdongas at the upstream (2.25%, p-value <.0001). It is expected that this paper will be useful for the researchers looking for soil moisture information in sub arid and subhumid zone at different topographic level to develop afforestation strategies based on species that can make the best use of soil water.

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Slope Stability from a Hydrological Perspective: Taking Typical Soil Slope as an Example

Advances in Civil Engineering ◽

10.1155/2020/1273603 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Yuelu Zhu ◽

Yaoting Xiao

Keyword(s):

Shear Strength ◽

Soil Moisture ◽

Moisture Content ◽

Slope Stability ◽

Soil Moisture Content ◽

Stable State ◽

Temporal Distribution ◽

Stability Factor ◽

Infiltration Capacity ◽

Increasing Trend

In the traditional research of slope stability, it is difficult to continuously obtain the moisture content of soil in long time sequences. In combination with the precipitation, temperature, and vegetation cover data in the study area, the variable infiltration capacity hydrological model is used to estimate the daily variation of soil moisture content, which is used as a calculation condition for the analysis of slope stability. The results show that, from 1970 to 2010, the spatial-temporal distribution of soil moisture content in the Weihe River Basin showed an increasing trend. Moreover, the shear strength of soil decreased, but the range was stable at approximately 2%. The strength reduction method based on the M-C inscribed circle criterion (DP3) shows that the slope stability factor k had an increasing trend for over 40 y. The portion of the period with a k value higher than 1.2 is more than 85% of the entire period, that with a k value between 1 and 1.2 is approximately 9%, and that with a k value less than 1 is approximately 5.5%. The R/S analysis results show that the Hurst coefficients of the τ-t curve and the k-t curve are 0.5568 and 0.5888, respectively, and that the slope is in a state of no variation. Based on these factors, the present and future of the slope is in a stable state. This scheme is a method of studying slope stability based on hydrology, and it provides a modern alternative for soil shear strength calculation and geological hazard assessment.

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Experimental Study on Shear Resistance of Carex-Root-Fibered Soil

Advances in Civil Engineering ◽

10.1155/2021/6680204 ◽

2021 ◽

Vol 2021 ◽

pp. 1-18

Author(s):

Feng-Chi Wang ◽

Ming-Ze Zhao ◽

Qi Sun

Keyword(s):

Shear Strength ◽

Soil Moisture ◽

Moisture Content ◽

Soil Moisture Content ◽

Friction Angle ◽

Fiber Content ◽

Soil Consolidation ◽

And Performance ◽

The Relationship ◽

Root Fiber

Carex shows strong vitality, adaptability, and performance with regard to soil consolidation and slope protection but is often disregarded as a weed. This study proposes to turn this so-called weed into treasure, using its characteristics to protect the slope. We studied the interaction between the carex roots and soil and compared it to other types of grass. To understand the interaction between the carex roots and soil, this study investigated the tensile properties of the carex root fibers. The effects of fiber content, humidity, distribution, and soil moisture content on the relationship between the shear strength and vertical pressure of the soil were analyzed using a direct shear test. Furthermore, the cohesion and internal friction angle were used to evaluate the shear strength of the root-fibered soil based on Mohr–Coulomb’s law. The results showed that the smaller the diameter, the shorter the length, and the greater the quantity and the lower the humidity of the root fibers, the higher the tensile strength of root fibers. In addition, the soil strength could be improved by the joint action of the roots and the soil. With an increase in the root fiber content and humidity, the soil moisture content decreased, whereas the shear strength of the carex-root-fibered soil increased. Here, four kinds of root fiber distributions, namely, “glyph,” “herringbone,” “eccentric,” and “vertical,” were chosen to study the shear strength of the root-fibered soil. The results showed that “glyph” root fiber distribution had the highest shear strength, while the shear strength decreased for the others.

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Constitutive Model of Shallow Landslides Catastrophe Theory under the Heavy Rainfall

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.166-169.2718 ◽

2012 ◽

Vol 166-169 ◽

pp. 2718-2721

Author(s):

Sheng Guo Cheng ◽

Hong Zheng

Keyword(s):

Shear Strength ◽

Soil Moisture ◽

Moisture Content ◽

Constitutive Model ◽

Catastrophe Theory ◽

Heavy Rainfall ◽

Soil Moisture Content ◽

Shallow Landslide ◽

Landslide Stability ◽

Function Relationship

Heavy rainfall has important implications to shallow landslide stability. In the paper, the relationship between the soil moisture content and soil shear strength and between surface displacements of landslide and rainfall were studied. Their statistical relationships were established. Relationship between soil moisture content and shear strength should be fitted using the logarithmic function. Relationship between soil slope and rainfall displacement should adopt the power function fit. Constitutive model of catastrophe theory of heavy rainfall landslides stability was known, which it is very important to provide a theoretical basis for prediction.

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Analysis on Soil Moisture Content in the Middle Reaches of the Yellow River

Arid Zone Research ◽

10.3724/sp.j.1148.2011.00085 ◽

2011 ◽

Vol 28 (1) ◽

pp. 85-91 ◽

Cited By ~ 2

Author(s):

Run-chun LI ◽

Xiu-zhi ZHANG ◽

Li-hua WANG ◽

Xin-yan LV ◽

Yuan GAO

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Soil Moisture Content ◽

Yellow River ◽

The Yellow River

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Analysis on Grey Correlation Degree of Soil Moisture Content under Different Land Use Types in Wind-Blown Sand Area

Arid Zone Research ◽

10.3724/sp.j.1148.2009.00840 ◽

2010 ◽

Vol 26 (6) ◽

pp. 840-845

Author(s):

Lin CHEN ◽

Lei WANG ◽

Qing-xia ZHANG ◽

Nai-ping SONG

Keyword(s):

Land Use ◽

Soil Moisture ◽

Moisture Content ◽

Soil Moisture Content ◽

Grey Correlation ◽

Land Use Types ◽

Correlation Degree ◽

Grey Correlation Degree

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Distribution of soil moisture content and its effect on the potential growth of the over-story species in North-East Chalkidiki

Silva Gandavensis ◽

10.21825/sg.v66i0.817 ◽

2001 ◽

Vol 66 ◽

Author(s):

M. Aslanidou ◽

P. Smiris

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Soil Moisture Content ◽

Soil Depth ◽

Moisture Distribution ◽

Taxus Baccata ◽

Mixed Stands ◽

Potential Growth ◽

North East ◽

Soil Moisture Distribution

This study deals with the soil moisture distribution and its effect on the potential growth and adaptation of the over-story species in north-east Chalkidiki. These species are: Quercus dalechampii Ten, Quercus conferta Kit, Quercus pubescens Willd, Castanea sativa Mill, Fagus moesiaca Maly-Domin and also Taxus baccata L. in mixed stands with Fagus moesiaca. Samples of soil, 1-2 kg per 20cm depth, were taken and the moisture content of each sample was measured in order to determine soil moisture distribution and its contribution to the growth of the forest species. The most important results are: i) available water is influenced by the soil depth. During the summer, at a soil depth of 10 cm a significant restriction was observed. ii) the large duration of the dry period in the deep soil layers has less adverse effect on stands growth than in the case of the soil surface layers, due to the fact that the root system mainly spreads out at a soil depth of 40 cm iii) in the beginning of the growing season, the soil moisture content is greater than 30 % at a soil depth of 60 cm, in beech and mixed beech-yew stands, is 10-15 % in the Q. pubescens stands and it's more than 30 % at a soil depth of 60 cm in Q. dalechampii stands.

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Mapping barrier island soil moisture using a radiative transfer model of hyperspectral imagery from an unmanned aerial system

Scientific Reports ◽

10.1038/s41598-021-82783-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Rehman S. Eon ◽

Charles M. Bachmann

Keyword(s):

Soil Moisture ◽

Radiative Transfer ◽

Moisture Content ◽

Layer Thickness ◽

Soil Moisture Content ◽

Hyperspectral Imagery ◽

Barrier Island ◽

Water Layer ◽

Radiative Transfer Model ◽

Transfer Model

AbstractThe advent of remote sensing from unmanned aerial systems (UAS) has opened the door to more affordable and effective methods of imaging and mapping of surface geophysical properties with many important applications in areas such as coastal zone management, ecology, agriculture, and defense. We describe a study to validate and improve soil moisture content retrieval and mapping from hyperspectral imagery collected by a UAS system. Our approach uses a recently developed model known as the multilayer radiative transfer model of soil reflectance (MARMIT). MARMIT partitions contributions due to water and the sediment surface into equivalent but separate layers and describes these layers using an equivalent slab model formalism. The model water layer thickness along with the fraction of wet surface become parameters that must be optimized in a calibration step, with extinction due to water absorption being applied in the model based on equivalent water layer thickness, while transmission and reflection coefficients follow the Fresnel formalism. In this work, we evaluate the model in both field settings, using UAS hyperspectral imagery, and laboratory settings, using hyperspectral spectra obtained with a goniometer. Sediment samples obtained from four different field sites representing disparate environmental settings comprised the laboratory analysis while field validation used hyperspectral UAS imagery and coordinated ground truth obtained on a barrier island shore during field campaigns in 2018 and 2019. Analysis of the most significant wavelengths for retrieval indicate a number of different wavelengths in the short-wave infra-red (SWIR) that provide accurate fits to measured soil moisture content in the laboratory with normalized root mean square error (NRMSE)< 0.145, while independent evaluation from sequestered test data from the hyperspectral UAS imagery obtained during the field campaign obtained an average NRMSE = 0.169 and median NRMSE = 0.152 in a bootstrap analysis.

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Estimating Agricultural Soil Moisture Content through UAV-Based Hyperspectral Images in the Arid Region

Remote Sensing ◽

10.3390/rs13081562 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1562

Author(s):

Xiangyu Ge ◽

Jianli Ding ◽

Xiuliang Jin ◽

Jingzhe Wang ◽

Xiangyue Chen ◽

...

Keyword(s):

Data Mining ◽

Soil Moisture ◽

Moisture Content ◽

Hyperspectral Imaging ◽

Fractional Order ◽

Arid Regions ◽

Soil Moisture Content ◽

Order Derivative ◽

Imaging Data ◽

Strategy I

Unmanned aerial vehicle (UAV)-based hyperspectral remote sensing is an important monitoring technology for the soil moisture content (SMC) of agroecological systems in arid regions. This technology develops precision farming and agricultural informatization. However, hyperspectral data are generally used in data mining. In this study, UAV-based hyperspectral imaging data with a resolution o 4 cm and totaling 70 soil samples (0–10 cm) were collected from farmland (2.5 × 104 m2) near Fukang City, Xinjiang Uygur Autonomous Region, China. Four estimation strategies were tested: the original image (strategy I), first- and second-order derivative methods (strategy II), the fractional-order derivative (FOD) technique (strategy III), and the optimal fractional order combined with the optimal multiband indices (strategy IV). These strategies were based on the eXtreme Gradient Boost (XGBoost) algorithm, with the aim of building the best estimation model for agricultural SMC in arid regions. The results demonstrated that FOD technology could effectively mine information (with an absolute maximum correlation coefficient of 0.768). By comparison, strategy IV yielded the best estimates out of the methods tested (R2val = 0.921, RMSEP = 1.943, and RPD = 2.736) for the SMC. The model derived from the order of 0.4 within strategy IV worked relatively well among the different derivative methods (strategy I, II, and III). In conclusion, the combination of FOD technology and the optimal multiband indices generated a highly accurate model within the XGBoost algorithm for SMC estimation. This research provided a promising data mining approach for UAV-based hyperspectral imaging data.

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