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Unsaturated Soil Water Retention Characteristics, Electrical Conductivity and Compressibility of a Poorly Graded Fujian Soil Amended with Biochar
(2026-07-01)
Liu, Allen
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Garg, Ankit
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Yanning, Wang
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Kamchoom, Viroon
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Zhussupbekov, Askar
This study investigates the effect of peach shell biochar on the unsaturated soil water retention characteristics, electrical conductivity (EC), and its correlation with the compressibility of poorly graded Fujian soil, thereby addressing a critical gap in biochar research for geotechnical applications. The study aims to explore an economical approach to accessing geotechnical properties using EC. Biochar (produced at 600 °C) was mixed with sand at 0%, 5%, and 10% ratios and tested using a modified oedometer for simultaneous EC and compressibility measurements. Results reveal that 10% biochar increased EC by 354 mS/m under 200 kPa stress, a fourfold enhancement over 5% biochar (88 mS/m), attributed to conductive pathways formed by biochar particles under compression. Soil settlement decreased by 17% (0.282ΔH) and 21% (0.268ΔH) at 5% and 10% biochar, respectively, compared to bare sand (0.340ΔH). The air-entry value surged from 0.40 kPa (bare sand) to 0.71 kPa (5% biochar) and 1.41 kPa (10% biochar), enhancing moisture retention by 78% and 253%. The EC-void ratio relationship diverged markedly: bare sand showed a declining EC with reduced void ratio (0.112 Δe), while biochar-amended soils exhibited a rising EC (Δe = 0.056 for 5% and 0.036 for 10%) due to particle conduction dominating over pore-water losses. These findings offer feasible geotechnical applications: the stress-responsive EC enables real-time stability monitoring in embankments or landfill covers via non-invasive resistivity tomography, while reduced compressibility positions biochar-amended sand as a sustainable alternative for foundations in flood-prone or arid regions. Enhanced air-entry values further mitigate drought-induced cracking and erosion. The dual role of biochar, improving conductivity and mechanical stability, supports its integration into green infrastructure strategies.
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Machine Learning-Based Prediction of Undrained Shear Strength in Marine Alluvial Clays: A Case Study of Bangkok
(2026-01-01)
Ramineni, Sai Krishna Akash
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Song, Zejun
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Garg, Ankit
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Kamchoom, Viroon
Accurate evaluation of undrained shear strength (Su) is crucial for the safe design of foundations and slopes in marine alluvial clays, including those commonly found in Bangkok. In this study, we assembled an automated machine learning (AutoML) workflow using open-source Python libraries to explore suitable predictive models for Su based on 152 undisturbed clay samples. The input variables considered include depth, moisture content, liquid limit, plastic limit, vane shear strength (PP), and total unit weight. Across the models evaluated, ridge regression offered a stable balance between accuracy and computational efficiency, with a mean absolute error of 0.550 t/m<sup>2</sup>, a root mean square error of 0.710 t/m<sup>2,</sup>, and an R² of 0.809, while requiring less than 0.05s of training time. The AutoML process facilitated a more transparent comparison of candidate algorithms, providing insight into variable relevance. Specifically, PP, depth, and unit weight emerged as the most influential predictors. Traditional index properties showed comparatively lower contributions. Five-fold cross-validation suggested that the selected model maintained consistent performance (mean R² = 0.810; standard deviation = 0.025). These results suggest that a streamlined AutoML workflow can aid in identifying reliable and easy-to-interpret models for Su estimation in Bangkok clays. Such an approach may complement laboratory testing and help reduce some of the uncertainty associated with empirical correlations, especially in preliminary design stages.
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Influence of soil density on gas permeability and water retention in soils amended with in-house produced biochar
(2021-06-01)
Garg, Ankit
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Huang, He
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Cai, Weiling
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Reddy, Narala Gangadhara
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Chen, Peinan
Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties (e.g. suction and water retention) of soil. However, variations in densities alter the properties of the soil–biochar mix. Such density variations are observed in agriculture (loosely compacted) and engineering (densely compacted) applications. The influence of biochar amendment on gas permeability of soil has been barely investigated, especially for soil with different densities. The major objective of this study is to investigate the water retention capacity, and gas permeability of biochar-amended soil (BAS) with different biochar contents under varying degree of compaction (DOC) conditions. In-house produced novel biochar was mixed with the soil at different amendment rates (i.e. biochar contents of 0%, 5% and 10%). All BAS samples were compacted at three DOCs (65%, 80% and 95%) in polyvinyl chloride (PVC) tubes. Each soil column was subjected to drying–wetting cycles, during which soil suction, water content, and gas permeability were measured. A simplified theoretical framework for estimating the void ratio of BAS was proposed. The experimental results reveal that the addition of biochar significantly decreased gas permeability k<inf>g</inf> as compared with that of bare soil (BS). However, the addition of 5% biochar is found to be optimum in decreasing k<inf>g</inf> with an increase of DOC (i.e. k<inf>g,65%</inf> > k<inf>g,80%</inf> > k<inf>g,95%</inf>) at a relatively low suction range (< 200 kPa) because both biochar and compaction treatment reduce the connected pores.
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Mechanism of biochar soil pore–gas–water interaction: gas properties of biochar-amended sandy soil at different degrees of compaction using KNN modeling
(2020-02-01)
Garg, Ankit
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Huang, He
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Kushvaha, Vinod
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Madhushri, Priyanka
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Kamchoom, Viroon
Soil compaction has contrasting effect on soil strength (i.e., positive) and vegetation growth (i.e., negative), respectively. Biochar has been utilized mostly in combination with soils in both agricultural fields (i.e., loose soils) and geo-structures (i.e., dense soil slopes, landfill cover) for improving water retention due to its microporous structure. Biochar is also found to be useful to reduce gas permeability in compacted soil recently. However, the efficiency of biochar in reducing gas permeability in loose and dense soils is rarely understood. The objective of this study is to analyze effects of compaction on gas permeability in soil at different degrees of compaction (i.e., 65%, 80% and 95%) and also different biochar amendment contents (0%, 5% and 10%). Another aim is to identify relative significance of parameters (soil suction, water content, biochar content and compaction) in affecting gas permeability. Experiments were conducted before applying k-nearest neighbor (KNN) modeling technique for identifying relative significance of parameters. Biochar was synthesized from a coastal invasive species (water hyacinth), which has relatively no influence on food chain (as unlike in biochar produced from biomass such as rice husk, straw, peanut shell). Based on measurements and KNN modeling, it was found that gas permeability of biochar-amended soil is relatively lower than that of soil without amendment. It was found from KNN model that for denser soils, higher amount of soil suction is mobilized for a significant increase in gas permeability as compared to loose soils. Among all parameters, soil suction is found to be most influential in affecting gas permeability followed by water content and compaction.
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Influence of physical and biochemical composition of three cellulose fibers on cracking of soil
(2019-01-01)
Boddu, Rishita
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Hong, Min
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Yongkang, Deng
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Fengjiao, Chen
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Garg, Ankit
Different soil improvement techniques have been used to intensify the engineering properties of soil. Three different lignocellulose fiber-reinforced (jute, coir and water hyacinth (WH)) have been explored on the desiccation potential of compacted clayey silt coil. The experimental methodology involved the mixing of fibers with soil at requisite amount and subjecting them to natural environment with controlled irrigating. The controlled irrigation comprised of 15 wetting/drying cycles for 105 days. Parameters like matric suction and water content were focused upon and recorded along with the surface crack formation. The data obtained from the field experiments were analyzed using the Artificial Neural Network (ANN) approach, which is developed in house using C++ language. From the analysis, it can be comprehended that coir is more effective as a reinforcement due to its multifilament nature and higher lignin content which is suitable in resisting crack formation. Further, optimization analysis and sensitivity analysis suggested mechanism of cracking for each fiber.

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