Cracking and erosion behaviors of sand–clay mixtures stabilized with microbial biopolymer and palm fiber

Drying-induced cracks and precipitation-induced erosion negatively impact the performance of soils in the context of extreme weather events. This study introduces two effective and sustainable materials, microbial biopolymer (MB) and palm fibers (PF), for cracking and erosion control in the sand-clay mixtures. A series of desiccation cracking tests, erosion tests, and SEM tests were conducted to evaluate the effectiveness of the treatment. The results showed that MB could significantly improve the resistance of the soil to cracking and scouring, and the improvement increased with increasing MB content. The optimum MB content was 0.15 % to achieve the maximum cracking and erosion resistance. For samples with varying sand contents, 0.15 % MB addition reduced the crack ratio, total crack length, and accumulative erosion ratio by 19.55 %-96.91 %, 4.22 %-99.58 %, and 57.88 %-89.53 %, respectively. In addition, PF positively affected the anti-crack and anti-erosion properties of the soil, and the application of 0.60 % PF had the best performance for both improvements. The cracks in the soils were mostly fine and shallow with the addition of 0.60 % PF, and therefore, the accumulative erosion ratio decreased by 44.18 %-62.76 % for samples with varying sand contents. Compared to the untreated soil, the degree of cracking and erosion was less due to the formation of a structure with more macropores and a sand skeleton in the treated samples with higher sand content. MB addition provides strong inter-particle bonding connections and a hydrophilic crust structure to improve the soils' resistance to cracking and erosion, while the fiber reinforcement effect benefits from interfacial friction and spatial restriction effects. This study provides mechanistic interpretations of desiccation cracking and erosion behavior in sand-clay mixtures under different treatments. It may guide the design of low-carbon technologies for geotechnical engineering applications.