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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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Increased erosion in biochar-amended soil: importance of integrating erosion control blankets and vegetation
(2026-03-01)
Hossain, Monir
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Jotisankasa, Apiniti
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Aramrak, Surachet
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Kamchoom, Viroon
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Nishimura, Satoshi
Although biochar is widely recognized for enhancing various soil properties, its impact on soil erosion resistance remains unclear and sometimes shows contradictory results. The main objective of this study is to quantify the effects of corn-cob biochar amendment, both with and without erosion control blankets (ECB), as well as the influence of biochar/compost incubation time on erosion resistance of a silty sand. The study also investigates the effects of biochar on Atterberg limits, shear strength, and thermal conductivity. As biochar content increases from 0 % to 20 %, the liquid limit (LL), plastic limit (PL), and shrinkage limit (SL) rise by 8 %–10 %, suggesting that biochar-amended soil (BAS) retains more water without losing strength. The addition of biochar has minimal impact on the shear strength of BAS at lower normal stresses (<45 kPa) but reduces its thermal conductivity by about 70 %. Submerged jet erosion tests show that biochar alone increases soil erosion in BAS. However, when combined with ECB and vegetation, erosion is significantly reduced (up to 39 %). Overall, this study underscores the importance of utilizing biochar in combination with ECB and such vegetation as ruzi grass to mitigate soil erosion in the silty sand.
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Modeling suction of unsaturated granular soil treated with biochar in plant microbial fuel cell bioelectricity system
(2025-12-01)
Onyelowe, K. C.
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Ebid, Ahmed M.
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Ramos Jiménez, Rosa Belén
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Kamchoom, Viroon
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Vishnupriyan, M.
There is an initiative driven by the carbon-neutrality nature of biochar in recent times, where various countries across Europe and North America have introduced perks to encourage the production of biochar for construction purposes. This objective aligns with the zero greenhouse emission targets set by COP27 for 2050. This research work seeks to assess the effectiveness of biochar in soils with varying grain size distributions in enhancing the soil–water characteristic curve (SWCC). This work further explores the effect of different combinations of biochar content (0 to 15 mass %) on the bioelectricity generation from biochar-improved plant microbial fuel cells (BPMFC). Additionally, different machine learning models such as the “Gradient Boosting (GB)”, “CN2 Rule Induction (CN2)”, “Naive Bayes (NB)”, “Support vector machine (SVM), “Stochastic Gradient Descent (SGD)”, “K-Nearest Neighbors (KNN)”, “Tree Decision (Tree)”, “Random Forest (RF)”, and “Response Surface Methodology” (RSM), have been developed to predict SWCC based on soil suction, electric current, electrical potential, volumetric water content, temperature, and bulk density. The newly established model demonstrates a reasonable ability to predict SWCC and a cheaper technology in predicting the suction of unsaturated soils in relation to the studied bioelectric factors of the BPMFC. Overall, in this research paper, the GB, SVM and CN2 outclassed the other regression techniques in this order thereby proposing the cheapest technology with the highest performance index to predict the SWCC behavior of unsaturated soils in a BPMFC system.
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Influence of biochar on the water permeability of compacted clay subjected to freezing–thawing cycles
(2024-06-01)
Chen, Zhongkui
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Kamchoom, Viroon
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Leung, Anthony Kwan
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Xue, Jiaxiang
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Chen, Rui
Seasonal variation of soil surface temperature, such as freezing and thawing, can induce increases in the water permeability in clay by mobilizing clay pore structure. This kind of weather-induced change in clay behavior may worsen the water-sealing performance during the construction and after closure operation of engineered structures such as soil barriers for tailings or man-made slopes. There is limited knowledge towards the influence of freezing–thawing cycles on clay microstructure and saturated permeability (K<inf>sat</inf>). This study investigated the saturated permeability of clay under freezing–thawing cycles and explored the uses of biochar as eco-friendly amendment to manipulate the permeability of compacted clay. Clay specimens were compacted with different initial water contents (30%, 34%, and 38%). The biochar application rates of 0%, 2%, 4%, 8% (by dry weight) were applied to measure their effects on the permeability of clay specimens. Saturated permeability was measured by the falling head tests. Any variation of biochar amended clay microstructure after freezing–thawing cycles was captured by the scanning electron microscope. The K<inf>sat</inf> was reduced by about one order of magnitude when the biochar application rate was larger than 4%. This may be attributed to the increase in the filling of the biochar particles in the clay intra-aggregate pores upon the transport of liquid water during the repeated freezing–thawing processes. The biochar may thus be recommended to minimize the K<inf>sat</inf> of geo-environmental structures in cold regions when sufficiently large application rate was used to facilitate the pore-filling process.
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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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