Back Analysis of Cihanjuang Landslide Using Finite Element Analysis with Shear Strength Reduction Method
Achmad Naufal Zayyan, Imam Achmad Sadisun, Indra Andra Dinata

Engineering Geology Laboratory, Faculty of Earth Science and Technology, Bandung Institute of Technology

Abstract

On January 9, 2021, a major landslide in Cihanjuang Village, Cimanggung District, Sumedang Regency, West Java, resulted in 40 deaths, 20 buildings buried, 26 buildings heavily damaged, and 350 buildings under threat. This study aimed to determine the residual shear strength parameters of the landslide using the back analysis method with Plaxis2D code. Site investigation was immediately conducted to obtain information of research area such as borehole sampling. Then, material parameters were identified through correlating N-SPT value, cone penetration tests, and laboratory analyses. Back analysis has been performed to show the slip surface location and the new instability parameters. The results indicated that the landslide failure was primarily due to the residual shear strength parameters of a silty clay layer, with cohesion at 3.534 kPa and an internal friction angle of 13.66 degrees. These findings provide crucial shear strength parameters for future slope redesign, reinforcement, and the design of new slopes under similar geotechnical conditions.

Keywords: back analysis, finite element method, landslide, shear strength reduction, slope stability

Topic: Interdisciplinary Earth Science and Technology