Behavior of Saturated Volcanic Soil Slopes with Grass Roots Under Seismic Response

Landslides on mountain slopes triggered by rainfall and earthquakes pose a significant risk to the slopes on Bali Island. This study examines the behavior of saturated volcanic soil reinforced with a combination of elephant grass and vetiver roots under earthquake forces. The methodology includes triaxial testing on vegetated soil and model testing to assess the reduction in landslide-prone areas due to vegetation. Triaxial test results indicated increased soil cohesion and internal friction angle when reinforced with vetiver and elephant grassroots. Cohesion in non-vegetated soil was measured at 0.20 kg/cm2, which increased to 0.65 kg/cm2 with root reinforcement. Model testing results aligned with consolidated undrained triaxial tests, demonstrating that the combination of vetiver and elephant grass reduced the landslide area by up to 64.1% on 45-degree slopes and up to 52.1% on 60-degree slopes.