Synergistic effects of drip irrigation and vegetation on the stability of biochar-stabilized expansive soil slopes

Existing studies have demonstrated that cracking is a fundamental cause of soil slope instability, while uneven water evaporation is the primary factor contributing to crack development. Appropriate moisture management measures can effectively reduce cracking risks. Therefore, investigating the mechanisms by which drip irrigation technology and vegetation influence expansive soil slopes holds significant theoretical and engineering importance. This study established four slope models: Biochar-Amended Expansive Soil Slope (BAES), Drip-Irrigated Biochar-Amended Expansive Soil Slope (DI-BAES), Vegetated Biochar-Amended Expansive Soil Slope (V-BAES), and Drip-Irrigated Vegetated Biochar-Amended Expansive Soil Slope (DI-V-BAES). An outdoor slope model box test was conducted over an entire summer season (100 days) to examine the effects of drip irrigation and vegetation on shallow stability of biochar-amended expansive soil slopes. Results show that drip irrigation and vegetation significantly impact the shallow stability. The drip irrigation system effectively maintains slope soil moisture through continuous water supply, thereby reducing soil drying and crack formation. Vegetation substantially improves soil shear strength, reduces soil scouring, and enhances erosion resistance through root reinforcement and canopy coverage. The combination of both measures further optimizes slope stability, with the DI-V-BAES model demonstrating the best performance in maintaining temperature stability, moisture content stability, reducing fissure rates, and improving scour resistance. This approach significantly enhances the overall stability and erosion resistance of expansive soil slopes, representing an effective measure for long-term slope stability. Additionally, drip irrigation promotes vegetation growth, increasing root density and slope-holding capacity, while vegetation improves soil cohesion and internal friction angle through root system development. In conclusion, the synergistic management model of drip irrigation and vegetation provides theoretical foundations and practical guidance for expansive soil slope protection.