干密度与含水率影响下生物炭对盐渍土渗透特性的调控机理OA

To address the excessively high permeability of saline soils that fails to meet the anti-see-page requirements of landfill cover layers,the mechanisms by which corn straw biochar regulates the permeability of saline soils were systematically investigated.Through variable head permeability tests,the effects of biochar content,dry density,and water content(gravimetric)on the permeability cha-racteristics of biochar-modified saline soil were systematically analyzed.The underlying regulatory mechanism was revealed at the microstructural level by combining scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)microscopic testing methods.The results show that both dry density and initial water content can affect the permeability of biochar-modified saline soil.The permeability coefficient decreases with increasing dry density,and the magnitude of this effect is governed by biochar content.The transition in the effect of dry density on the dispersion of permeability coefficient occurs at a biochar content of 5%:at a low dosage,the dispersion decreases with increasing dry density,whereas at a high dosage,it increases with increasing dry density.This is attributed to the fact that at high biocher contents,the biochar particles tend to saturate the effective seepage channels in the soil and form compaction-resistant aggregates with soil particles,thus diminishing the marginal effect of further compaction on reducing the permeability coefficient.As the biochar content increases,the permeability coefficient responds to the initial water content in a continuous manner,changing from a positive correlation to a gradual flattening and then to a negative correlation.Microscopic analysis re-veals that the abundant functional groups on biochar surfaces suppress concentrated salt crystallization via adsorption,while its porous structure provides dispersed nucleation sites for salt crystallization,thereby mitigating salt blockage of the original seepage channels and helping maintain permeability sta-bility.MIP results show that as biochar content increases from 0%to 15%,the macropore volume frac-tion decreases from 62.3%to 41.5%,with a corresponding reduction in pore connectivity.These findings provide a theoretical basis and technical reference for the improved application of saline soils in anti-seepage engineering projects.