Evaluation the Slope Movement and Effectiveness the Remedial Measures of Volcanic Residual Soil in Yogyakarta, Indonesia

Abstract Among influence factors of slope stability, rainfall is the most triggering factor. When rainwater flows through the slip surface, it will cause slope movement. This paper studies the slope movement in Kalibawang irrigation channel at km. 15+900, which induced failure of the irrigation channel and other surrounding structures. The slope movement was modelled as coupled stress-pore water pressure analysis using SIGMA/W. Satellite-based rainfall data of Tropical Rainfall Measuring Mission (TRMM) was collected from 1 July to 30 August 2017. The numerical model was validated with the field monitoring for deformation and pore water pressure to obtain a reliable soil parameter. Several attempts have been made to obtain an acceptable of E parameter by determining the smallest root mean square error (RMSE) value of deformation and larger coefficient of relation (R2). The numerical model has been extended to evaluate the slope stability after remedial work using piles. Six rainfall scenario were applied to model. The analysis concludes that the piling works increases the slope stability under several rainfall scenarios, which is indicated by increase in factor of safety.