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Ankit Garg - One of the best experts on this subject based on the ideXlab platform.
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Genetic programming model for estimating Soil Suction in shallow Soil layers in the vicinity of a tree
Engineering Geology, 2020Co-Authors: Zhi-liang Cheng, Wan-huan Zhou, Ankit GargAbstract:Abstract Soil Suction, an important parameter in the safety and risk assessment of geotechnical and green infrastructures, is greatly affected by plants and weather in the shallow Soil layers of urban landscapes/green infrastructure. In this study, a computational model consisting of a drying-cycle model and wetting-cycle model was developed by means of a genetic programming method to depict variations in Soil Suction using select influential parameters. The input data in the model development were measured in a field monitoring test on the campus of the University of Macau. Soil Suction was quantified by field monitoring at different distances (0.5 m, 1.5 m, and 3.0 m) from a tree, at a constant depth of 20 cm, with selected influential parameters including initial Soil Suction, air humidity, rainfall amount, cycle duration, and ratio of distance from tree to tree canopy. Based on the performance analysis, the efficiency and reliability of the proposed computational model are validated. The importance of each input and the coupled effect of each two input variables on the output were investigated using global sensitivity analysis. It can be concluded that the proposed computational model based on the artificial intelligence simulation method describes the relationship between field Soil Suction in drying–wetting cycles and select input variables within an acceptable degree of error. Accordingly, it can serve as a tool for supporting geotechnical construction design and for assessing the safety and risk of geotechnical green infrastructures.
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Assessment of the coupled effects of vegetation leaf and root characteristics on Soil Suction: an integrated numerical modeling and probabilistic approach
Acta Geotechnica, 2019Co-Authors: Hong Zhu, S. Sreedeep, M. Indupriya, Vinay Kumar Gadi, Guoxiong Mei, Ankit GargAbstract:Root depth and leaf area ratio are two important features of a plant and exhibit a coupled relation. Assessing their coupled effects on induced Soil Suction is essential for analyzing the performance of a green infrastructure, such as water storage/drainage in green roofs and stability of a vegetated slope. Previously Soil moisture induced by vegetation was often presented deterministically without considering the overall effects of leaf and root characteristics in a probabilistic manner. The main objective of this study is to investigate the influence of coupled variations in root and leaf characteristics on vegetation-induced Soil Suction. In addition, the coupled effects were analyzed using statistical approach. Different combinations of the leaf area index and root depth of the same plant were assessed. Probabilistic analysis was then conducted by computing Suction profiles in form of quantiles. It was found that the biggest variability in Suction profiles occurs at around 0.6 times the root depth and the minimum occurred at near surface and at maximum root depth. This depth at 0.6 times root depth corresponds to the maximum root density. It implies that the probabilistic analysis becomes more and more important while assessing Suction profiles near the maximum root density.
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Prediction of Vegetation-Induced Soil Suction Using Numerical Modelling and AI
Proceedings of the 8th International Congress on Environmental Geotechnics Volume 2, 2018Co-Authors: M. Indu Priya, Ankit Garg, S. Sreedeep, Ajit K. Sarmah, Nik Norsyahariati Nik DaudAbstract:Study of Soil Suction is important in design and implementation of slope stability and erosion control measures. In order to conduct a realistic analysis of performance of sustainable green infrastructure, it is essential to address the uncertainties in Suction induced by vegetation due to variability in their leaf and root characteristics, evapotranspiration (ET) and initial conditions of the Soil. The objective of this study is to investigate the combined influence leaf area index (LAI), root depth, ET rate and initial Suction of Soil on root water uptake-induced Soil Suction. A parametric numerical study was performed with 480 simulations using HYDRUS to carry out the finite element analysis. The study was done on completely decomposed granite (CDG) Soil and vegetation species used was Schefflera heptaphylla. It was observed that although if independently considered, vegetation with higher LAI provided greater mechanical stability, when combined with higher ET rates or initial Suction, the Suction induced may lead to wilting of the vegetation. Artificial intelligence technique such as Artificial neural network (ANN) was used to predict matric Suction at any given depth using the results obtained from the numerical simulations. Performance of the best model indicated that ANN was able to successfully predict the vegetation-induced matric Suction.
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relationships between leaf and root area indices and Soil Suction induced during drying wetting cycles
Ecological Engineering, 2016Co-Authors: Ankit Garg, Anthony Kwan Leung, Billy C.h. HauAbstract:Abstract The stability and serviceability of geotechnical infrastructure may be affected by plant-induced Soil Suction during drying–wetting cycles, because an increase in Suction would reduce hydraulic conductivity and also increase shear strength. Recent studies have been conducted to quantify Suction induced during evapotranspiration (ET) and ponding in Soil vegetated with non-crop species that are used for the ecological restoration of geotechnical infrastructure. However, induced Suction distribution under drying–wetting cycles is rarely studied. The objectives of this study are to (1) quantify Suction induced by a non-crop tree species, Schefflera heptaphylla, under ponding–drying–ponding cycles and (2) correlate intercepted radiant energy, tree leaf area index (LAI), extinction coefficient (k) and root area index (RAI) with Suction. In total, 18 vegetated Soil samples with LAI ranging from 0.9 to 3.1 and three bare Soil samples (control) were tested and subjected to identical cycles of ET and ponding. Energy balance calculation was performed to determine the percentage of interception of radiant energy. An almost linear relationship can be seen between the percentage of energy intercepted (from 7% to 42% ± 4%) and LAI (from 0.9 to 3.1 ± 0.09) for S. heptaphylla. The measured value of k for S. heptaphylla (0.13) was found to be much lower than that of some crop species (0.4–1.6) reported in the literature. Peak Suction is always identified at the depth, where RAI is maximum. It was further demonstrated that the tree-induced Suction has a strong linear correlation with both the RAI and LAI.
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Relationships between leaf and root area indices and Soil Suction induced during drying–wetting cycles
Ecological Engineering, 2016Co-Authors: Ankit Garg, Anthony Kwan Leung, Billy C.h. HauAbstract:Abstract The stability and serviceability of geotechnical infrastructure may be affected by plant-induced Soil Suction during drying–wetting cycles, because an increase in Suction would reduce hydraulic conductivity and also increase shear strength. Recent studies have been conducted to quantify Suction induced during evapotranspiration (ET) and ponding in Soil vegetated with non-crop species that are used for the ecological restoration of geotechnical infrastructure. However, induced Suction distribution under drying–wetting cycles is rarely studied. The objectives of this study are to (1) quantify Suction induced by a non-crop tree species, Schefflera heptaphylla, under ponding–drying–ponding cycles and (2) correlate intercepted radiant energy, tree leaf area index (LAI), extinction coefficient (k) and root area index (RAI) with Suction. In total, 18 vegetated Soil samples with LAI ranging from 0.9 to 3.1 and three bare Soil samples (control) were tested and subjected to identical cycles of ET and ponding. Energy balance calculation was performed to determine the percentage of interception of radiant energy. An almost linear relationship can be seen between the percentage of energy intercepted (from 7% to 42% ± 4%) and LAI (from 0.9 to 3.1 ± 0.09) for S. heptaphylla. The measured value of k for S. heptaphylla (0.13) was found to be much lower than that of some crop species (0.4–1.6) reported in the literature. Peak Suction is always identified at the depth, where RAI is maximum. It was further demonstrated that the tree-induced Suction has a strong linear correlation with both the RAI and LAI.
Yusuf Erzin - One of the best experts on this subject based on the ideXlab platform.
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artificial neural networks approach for swell pressure versus Soil Suction behaviour
Canadian Geotechnical Journal, 2007Co-Authors: Yusuf ErzinAbstract:In this study, the swell pressure versus Soil Suction behaviour was investigated using artificial neural networks (ANNs). To achieve this, the results of the total Suction measurements using thermocouple psychrometer technique and constant-volume swell tests in oedometers performed on statically compacted specimens of Bentonite–Kaolinite clay mixtures with varying Soil properties were used. Two different ANN models have been developed to predict the total Suction and swell pressure. The ANNs results were compared with the experimental values and found close to the experimental results. Moreover, several performance indices such as correlation coefficient, variance account for (VAF), and root mean square error (RMSE) were calculated to check the prediction capacity of the ANN models developed. Both ANN models have shown a high prediction performance based on the performance indices. Therefore, it can be concluded that the initial Soil Suction is the most relevant state of Suction that characterizes the pot...
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swell pressure prediction by Suction methods
Engineering Geology, 2007Co-Authors: Yusuf Erzin, Orhan ErolAbstract:Soil Suction is the most relevant Soil parameter for characterization of the swell behavior. An attempt was made to predict swell pressures from Soil Suction measurements. In this study, Na-bentonite was mixed with kaolinite in the ratios of 5, 10, 15, 20 and 25% of dry kaolinite weight to obtain Soils in a wide range of plasticity indices (i.e. 30, 50, 68, 84 and 97%). Suction measurements using thermocouple psychrometer technique were made on statically compacted specimens. The dependence of Soil Suction on water content, dry density and bentonite content was examined. Soil Suction was correlated to the Soil properties, namely, water content, plasticity index, dry density, cation exchange capacity and specific surface area using multiple regression analyses. The correlations revealed a simple regression equation for a quick prediction of Soil Suctions from easily determined Soil properties. In order to investigate Soil Suction versus swell pressure behavior, the results of standard constant volume swell tests (ASTM, 1990) performed on statically compacted samples of these clay mixtures were used. A linear relationship was established between the logarithm Soil Suction and the swell pressure. It was also found that an experimental relationship which would directly relate the initial Soil Suction to the swell pressure can be established.
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Artificial neural networks approach for swell pressure versus Soil Suction behaviour
Canadian Geotechnical Journal, 2007Co-Authors: Yusuf ErzinAbstract:In this study, the swell pressure versus Soil Suction behaviour was investigated using artificial neural networks (ANNs). To achieve this, the results of the total Suction measurements using thermo...
John Bryant - One of the best experts on this subject based on the ideXlab platform.
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Variation of Soil Suction with Depth in Dallas and Fort Worth, Texas
Transportation Research Record: Journal of the Transportation Research Board, 1998Co-Authors: John BryantAbstract:The variation of Soil Suction and the estimate of constant Soil Suction with depth is used to design many slab-on-grade foundations and pavement moisture barriers. The Post-Tensioning Institute’s design procedures for slab-on-grade foundations and design of vertical pavement moisture barriers use the constant Suction at depth to predict differential Soil movements that influence shear, deflection, and moment magnitudes and the effective barrier depth. Constant Soil Suction estimates can be correlated to the climate or long-term weather conditions at any given site by using the Thornthwaite moisture index (TMI), which estimates the amount of net moisture surplus or deficit from precipitation and evapotranspiration of moisture from the ground surface. On the basis of the empirical curves, the constant value of total Soil Suction for the Dallas–Fort Worth, Texas (DFW) area is about 246 kPa based on an average TMI of 0. Analysis of more than 1,200 total Soil Suction laboratory tests performed on developed and undeveloped lots indicates that the measured average total Soil Suction value in the upper 6 m is closer to 979 kPa for the DFW area ranging between 55 kPa and 11,246 kPa during the 1995–1997 period. Some hypothesized reasons for the difference between the empirical and measured equilibrium (constant) Soil Suction values are amounts of clay, clay origin, variable plasticity indexes, soluble salt content, and equilibration curve differences.
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Variation of Soil Suction with Depth in Dallas and Fort Worth, Texas
Transportation Research Record, 1998Co-Authors: John BryantAbstract:The variation of Soil Suction and the estimate of constant Soil Suction with depth is used to design many slab-on-grade foundations and pavement moisture barriers. The Post-Tensioning Institute's design procedures for slab-on-grade foundations and design of vertical pavement moisture barriers use the constant Suction at depth to predict differential Soil movements that influence shear, deflection, and moment magnitudes and the effective barrier depth. Constant Soil Suction estimates can be correlated to the climate or long-term weather conditions at any given site by using the Thornthwaite moisture index (TMI), which estimates the amount of net moisture surplus or deficit from precipitation and evapotranspiration of moisture from the ground surface. On the basis of the empirical curves, the constant value of total Soil Suction for the Dallas-Fort Worth, Texas (DFW) area is about 246 kPa based on an average TMI of 0. Analysis of more than 1,200 total Soil Suction laboratory tests performed on developed and...
Anthony Kwan Leung - One of the best experts on this subject based on the ideXlab platform.
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effects of planting density on tree growth and induced Soil Suction
Geotechnique, 2016Co-Authors: Charles Wang Wai Ng, Anthony Kwan Leung, Junjun Ni, Chao Zhou, Zijian WangAbstract:Plant evapotranspiration is recognised to affect Soil Suction of slopes and landfill covers. Previous work has focused on evapotranspiration-induced Suction by a single plant, with little attention paid to the effects of planting density. The aim of this study is to quantify any changes in tree growth and tree-induced Suction during evapotranspiration and rainfall under different planting densities for non-mixed-species plantations. A tree species, Schefflera heptaphylla, which is commonly found in Asia, was planted in silty sand at spacings of 60, 120 and 180 mm, representing three different planting densities. For each case, three replicates were tested to consider tree variability. In total, the responses of Suction for 297 seedlings subjected to drying and a rainfall event with a 10-year return period were measured. The test results show that reducing the tree spacing from 180 to 60 mm induced greater tree–tree competition for water, as indicated by a 364% increase in peak Suction upon evapotranspirat...
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relationships between leaf and root area indices and Soil Suction induced during drying wetting cycles
Ecological Engineering, 2016Co-Authors: Ankit Garg, Anthony Kwan Leung, Billy C.h. HauAbstract:Abstract The stability and serviceability of geotechnical infrastructure may be affected by plant-induced Soil Suction during drying–wetting cycles, because an increase in Suction would reduce hydraulic conductivity and also increase shear strength. Recent studies have been conducted to quantify Suction induced during evapotranspiration (ET) and ponding in Soil vegetated with non-crop species that are used for the ecological restoration of geotechnical infrastructure. However, induced Suction distribution under drying–wetting cycles is rarely studied. The objectives of this study are to (1) quantify Suction induced by a non-crop tree species, Schefflera heptaphylla, under ponding–drying–ponding cycles and (2) correlate intercepted radiant energy, tree leaf area index (LAI), extinction coefficient (k) and root area index (RAI) with Suction. In total, 18 vegetated Soil samples with LAI ranging from 0.9 to 3.1 and three bare Soil samples (control) were tested and subjected to identical cycles of ET and ponding. Energy balance calculation was performed to determine the percentage of interception of radiant energy. An almost linear relationship can be seen between the percentage of energy intercepted (from 7% to 42% ± 4%) and LAI (from 0.9 to 3.1 ± 0.09) for S. heptaphylla. The measured value of k for S. heptaphylla (0.13) was found to be much lower than that of some crop species (0.4–1.6) reported in the literature. Peak Suction is always identified at the depth, where RAI is maximum. It was further demonstrated that the tree-induced Suction has a strong linear correlation with both the RAI and LAI.
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Relationships between leaf and root area indices and Soil Suction induced during drying–wetting cycles
Ecological Engineering, 2016Co-Authors: Ankit Garg, Anthony Kwan Leung, Billy C.h. HauAbstract:Abstract The stability and serviceability of geotechnical infrastructure may be affected by plant-induced Soil Suction during drying–wetting cycles, because an increase in Suction would reduce hydraulic conductivity and also increase shear strength. Recent studies have been conducted to quantify Suction induced during evapotranspiration (ET) and ponding in Soil vegetated with non-crop species that are used for the ecological restoration of geotechnical infrastructure. However, induced Suction distribution under drying–wetting cycles is rarely studied. The objectives of this study are to (1) quantify Suction induced by a non-crop tree species, Schefflera heptaphylla, under ponding–drying–ponding cycles and (2) correlate intercepted radiant energy, tree leaf area index (LAI), extinction coefficient (k) and root area index (RAI) with Suction. In total, 18 vegetated Soil samples with LAI ranging from 0.9 to 3.1 and three bare Soil samples (control) were tested and subjected to identical cycles of ET and ponding. Energy balance calculation was performed to determine the percentage of interception of radiant energy. An almost linear relationship can be seen between the percentage of energy intercepted (from 7% to 42% ± 4%) and LAI (from 0.9 to 3.1 ± 0.09) for S. heptaphylla. The measured value of k for S. heptaphylla (0.13) was found to be much lower than that of some crop species (0.4–1.6) reported in the literature. Peak Suction is always identified at the depth, where RAI is maximum. It was further demonstrated that the tree-induced Suction has a strong linear correlation with both the RAI and LAI.
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Comparisons of Soil Suction induced by evapotranspiration and transpiration of S. heptaphylla
Canadian Geotechnical Journal, 2015Co-Authors: Ankit Garg, Anthony Kwan Leung, Charles Wang Wai NgAbstract:For a given evapotranspiration (ETr), both Soil evaporation and plant transpiration (Tr) would induce Soil Suction. However, the relative contribution of these two processes to the amount of Suction induced is not clear. The objective of this study is to quantify ETr- and Tr-induced Suction by a selected tree species, Scheffllera heptaphylla, in silty sand. The relative contribution of transpiration and evaporation to the responses of Suction is then explored based on observed differences in Tr- and ETr-induced Suction. In total, 12 test boxes were used for testing: 10 for vegetated Soil with different values of leaf area index (LAI) and root area index (RAI), while two were for bare Soil as references. Each box was exposed to identical atmospheric conditions controlled in a plant room for monitoring Suction responses over a week. Due to the additional effects of Soil evaporation, ETr-induced Suction could be 3%–47% higher than Tr-induced Suction, depending on LAI. The significance of evaporation reduced ...
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Comparisons of Soil Suction induced by evapotranspiration and transpiration of S. heptaphylla
Canadian Geotechnical Journal, 2015Co-Authors: Ankit Garg, Anthony Kwan Leung, Charles Wang Wai NgAbstract:For a given evapotranspiration (ETr), both Soil evaporation and plant transpiration (Tr) would induce Soil Suction. However, the relative contribution of these two processes to the amount of Suction induced is not clear. The objective of this study is to quantify ETr- and Tr-induced Suction by a selected tree species, Scheffllera heptaphylla, in silty sand. The relative contribution of transpiration and evaporation to the responses of Suction is then explored based on observed differences in Tr- and ETr-induced Suction. In total, 12 test boxes were used for testing: 10 for vegetated Soil with different values of leaf area index (LAI) and root area index (RAI), while two were for bare Soil as references. Each box was exposed to identical atmospheric conditions controlled in a plant room for monitoring Suction responses over a week. Due to the additional effects of Soil evaporation, ETr-induced Suction could be 3%–47% higher than Tr-induced Suction, depending on LAI. The significance of evaporation reduced ...
Guy Richard - One of the best experts on this subject based on the ideXlab platform.
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Soil compaction by wheeling: changes in Soil Suction caused by compression
European Journal of Soil Science, 2010Co-Authors: Kai Cui, Yu-jun Cui, P. Défossez, Guy RichardAbstract:Soil compaction caused by agricultural machinery has been increasingly recognized as a considerable problem facing intensive agriculture. Most of the models used to estimate Soil deformation during the passage of machines are based on the concept of total stress: they have neglected an important stress variable for unsaturated Soils; that is, the matric Suction. The aim of the present work was to evaluate the validity of this hypothesis by studying Suction variation during a static compression test. A standard oedometer cell equipped with a tensiometer was used to measure Soil Suction in situ for different vertical stresses. Measurements were carried out on remoulded Soil samples obtained by compacting a loamy Soil at different initial water Suctions (
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Soil compaction by wheeling: change in Soil Suction due to compression
European Journal of Soil Science, 2010Co-Authors: Kai Cui, Yu-jun Cui, P. Défossez, Guy RichardAbstract:Soil compaction due to traffic has been increasingly recognized as a considerable problem facing intensive agriculture. Most of the models used to estimate Soil deformation during the passage of machines are based on the concept of total stress: then they have neglected an important stress variable for unsaturated Soils, i.e. the matrix Suction. The aim of the present work is to evaluate the validity of this hypothesis by studying Suction variation during a static compression test. A standard oedometer cell equipped with a tensiometer was used to measure Soil Suction in situ for different vertical stresses. Measurements were carried out on remoulded Soil samples obtained by compacting a loamy Soil at different initial water Suctions (< 100 kPa). The results showed that the Suction remained almost constant until a stress threshold value t beyond which the Suction decreased as the stress increased. This stress threshold increased with the initial Suction. These results corroborated the hypothesis of a constant Suction during deformation usually assumed to model Soil compaction during traffic for Soils with Suction higher than 20 kPa. The results obtained highlighted the effect of Soil structure on the stress threshold: t was found to be higher for Soil samples with initial aggregates < 2 mm for those with initial aggregates < 0.4 mm. This was interpreted at pore scale by comparing qualitatively the evolution of pore-size distribution and the expected distribution of water in the pores. This interpretation was based on pore-size distribution measurement by mercury intrusion.