Landslide Potential in Cihanjuang, Cimanggung, Sumedang, West Java Province

Abstract

Landslides occurred in the Cihanjuang area, Cimanggung, Sumedang Regency, West Java on January, 9th 2021 with 40 fatalities and several buildings severely damaged. This area is in the form of hills with a fairly steep slope and housing is built on it. Geologically, the research area is composed of Undecomposed Young Volcanoes (Qyu) in the form of tuffaceous sand, lapilli, breccias, lava, and agglomerates. The research aims to determine the potential and volume of landslides. The research method used is conducting geotechnical testing and carrying out topographical mapping. Geotechnical tests carried out were water content, specific gravity, sieve analysis, hydrometer, and direct shear strength. The geotechnical test results showed that water content: 16.37% – 31.26%, cohesion: 59.2 kPa – 112.7 kPa, and internal friction angle: 6.30° – 30.50°, percentage of gravel and sand 11.10 % – 34.90 %, percentage of silt and clay 65.10 % – 88.90 %. According to USCS, this soil sample includes the MH-CH-OH classification Topographical mapping was carried out covering an area of 7.006 hectares. The internal friction angle is relatively steep, and the percentage of gravel and sand is quite high, so water infiltration becomes easy, so the Cimanggung area has a high potential for landslides. From the topographic mapping, the volume of the landslide was around 161.981 m³. To maintain slope stability and avoid landslides, apart from planting strong-rooted plants in areas with high elevations, they also manage the drainage by making waterways on the northwest and southeast sides of the steep slopes to the main road.