Biochar stabilises vegetated expansive slopes by way of moisture and temperature regulation

Shallow soil desiccation in expansive soil slopes can induce cracking, triggering slope failure. Previous studies have demonstrated that incorporating 5% corn stover biochar into expansive soil can effectively enhance the soil’s water retention capacity and inhibit crack development. To investigate the impact of adding 5% corn stover biochar on the stability of expansive soil slopes under vegetation-covered conditions, this study establishes two groups of expansive soil slope models overlaid with Manila grass, one modified with biochar and the other without. Over 60 days under natural conditions, vegetation growth, shallow soil temperature variations, and moisture content changes were monitored. Results indicate that biochar-amended slopes exhibited a higher leaf area index compared with untreated slopes, demonstrating that biochar promotes plant growth. In addition, biochar application reduced soil temperature and minimised thermal fluctuations, thereby lessening atmospheric weathering effects on shallow soil layers. The volumetric water content in biochar-treated slopes showed more stable behaviour, limiting crack propagation and improving slope stability. These findings highlight biochar’s potential as a sustainable solution for stabilising expansive soil slopes by enhancing vegetation performance, regulating soil temperature, and maintaining moisture equilibrium, thus reducing environmental degradation risks.