Effects of biochar on hydraulic conductivity of compacted kaolin clay
2018
Wong, James Tsz Fung | Chen, Zhongkui | Wong, Annie Yan Yan | Ng, Charles Wang Wai | Wong, Ming Hung
Compacted clay is widely used as capillary barriers in landfill final cover system. Recently, biochar amended clay (BAC) has been proposed as a sustainable alternative cover material. However, the effects of biochar on saturated hydraulic conductivity (kₛₐₜ) of clay with high degree of compaction is not yet understood. The present study aims to investigate the effects of biochar on kₛₐₜ of compacted kaolin clay. Soil specimens were prepared by amending kaolin clay with biochar derived from peanut-shell at 0, 5 and 20% (w/w). The kₛₐₜ of soil specimens was measured using a flexible water permeameter. The effects of biochar on the microstructure of the compacted clay was also investigated using MIP. Adding 5% and 20% of biochar increased the kₛₐₜ of compacted kaolin clay from 1.2 × 10⁻⁹ to 2.1 × 10⁻⁹ and 1.3 × 10⁻⁸ ms⁻¹, respectively. The increase in kₛₐₜ of clay was due to the shift in pore size distribution of compacted biochar-amended clay (BAC). MIP results revealed that adding 20% of biochar shifted the dominant pore diameter of clay from 0.01–0.1 μm (meso– and macropores) to 0.1–4 μm (macropores). Results reported in this communication revealed that biochar application increased the kₛₐₜ of compacted clay, and the increment was positively correlated to the biochar percentage.
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