Earth-fill Dam Seepage Safety Risk Assessment: Randugunting Dam, Blora

Earth-fill dam, the most common dam, is constructed primarily using compacted earth materials from surrounding areas. Despite its simplicity, these dams have higher chances of failures caused by seepage or sliding. Randugunting Dam is an earth-fill dam located in the northern part of Blora, Central Java. This dam was built to accommodate irrigation and domestic needs in Blora, Pati, and Rembang Regencies. This study is conducted to monitor and assess the present Randugunting Dam’s seepage condition using Finite Element Analysis (FEA) and calculate the seepage safety factor. Geological and engineering geological mapping are combined by coring data to understand the rock and soil characteristics of the main dam location. The seepage rate analysis is conducted using Finite Element Analysis on GeoStudio 2021 SEEP/W. The results showed that Randugunting’s main dam and reservoir area primarily comprises calcareous siltstone, carbonaceous sandstone, claystone, and limestone. Weathering rates in this area range from slightly weathered to highly weathered. The seepage rate from FEA ranges from 4.39 - 5.31 litre/s and calculation of safety factor along the Randugunting Main Dam is 4.49. Those values are considered to be safe. Installing blanket type of horizontal drain and seepage berm can act as prevention step in the future.