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    Item type:Publication,
    Seasonal dynamics of root growth and desiccation cracks and their effects on soil hydraulic conductivity
    (2025-04-01)
    Yuliana, Yuliana
    ;
    Apriyono, Arwan
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    Kamchoom, Viroon
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    Boldrin, David
    ;
    Cheng, Qing
    Vegetation significantly influences soil hydraulic conductivity, with the extent of this influence depending on root morphology and density, which vary across different developmental stages of plants. This research investigates the interaction dynamics between plant roots (during both growth and decay) and desiccation cracks, as well as the combined impact of vegetation, cracks, and seasonal variations on soil hydraulic conductivity (K<inf>sat</inf>). Root growth and decay patterns were observed using a minirhizotron, while changes in crack formation were monitored and interpreted using the Crack Intensity Factor (CIF) for both vegetated and bare areas over an eighteen-month period of wetting and drying cycles. K<inf>sat</inf> was analysed based on data from a double-ring test. The findings indicate that the presence of vetiver roots results in a less visible and uneven crack distribution compared to bare soil, with CIF and average crack widths reduced by half. However, cracks reappear during root decay periods. Although cracks were minimised in vegetated soil, K<inf>sat</inf> values increased significantly during dry periods, with a 16-fold rise in the vegetated zone due to root propagation, while the bare zone showed a marginal 5-fold increase. The presence of cracks and roots significantly influences K<inf>sat</inf>, exhibiting distinct hysteresis behaviour in response to drying and wetting cycles.
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    Item type:Publication,
    Landfill gas emission through compacted clay considering effects of crack pathway and intensity
    (2022-04-15)
    Chen, Zhongkui
    ;
    Kamchoom, Viroon
    ;
    Chen, Rui
    Compacted clay barrier plays an important role in reducing landfill gas transport due to its low gas permeability. There is limited understanding of desiccation cracks and to what extent they can cause preferential pathways of landfill gas through compacted clay barriers. This study investigated the intensity and pathway of desiccation cracks as well as its effects on gas emission through compacted clay. The compacted clay with and without scratched compaction interface was subjected to drying to simulate desiccation cracks. The clay was then extruded from large containers into one dimensional columns to allow observation of crack propagation using an X-ray computerized tomography scanner. After that, gas emission rate was measured from each column under different gas pressures (i.e., 1, 5, 10 and 20 kPa). Furthermore, a simplified method is proposed to predict gas emission rate with consideration of intensity and characteristics of cracks. Test results demonstrated that desiccation cracks were initiated mainly at the center of each container (i.e., within 40% of container dimension). Gas emission rate can be increased at least 10 times with the presence of desiccation cracks (i.e., at gas pressure of 5 kPa). As compared to the depth and continuous pathway of cracks which significantly increased gas emission rate, the discontinuous crack pathway can reduce the gas emission rate by up to 3 times. The findings towards crack characteristics and gas emission observed in this study are crucial for safety design and long-term operation of compacted clay barriers in landfill covers.
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    Item type:Publication,
    Influence of physical and biochemical composition of three cellulose fibers on cracking of soil
    (2019-01-01)
    Boddu, Rishita
    ;
    Hong, Min
    ;
    Yongkang, Deng
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    Fengjiao, Chen
    ;
    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.