SEEPAGE ANALYSIS ON THE EMBANKMENT BODY ZONAL TYPE DAM IN BAGONG EAST JAVA INDONESIA

Abstract

Dam construction is one form of water resource utilization in Indonesia. In addition to its potential functions and benefits, dams in Indonesia also pose significant risks. Therefore, detailed planning for dam construction is essential. The Bagong Dam has a zonal embankment type with a vertical core. This type of dam has larger pores or voids compared to concrete/asphalt dams. Consequently, a detailed seepage calculation is necessary to avoid adverse events. Water seepage can be addressed by analyzing it using the Geo-Studio software, which can identify the depression line, as well as the velocity and discharge of seepage through the dam body. The analysis includes conditions such as Normal Water Surface (NWS), Flood Water Surface (FWS), Rapid Drawdown, and Dead Storage. The analysis will produce seepage patterns (depression lines), seepage discharge, and seepage velocity. The calculated seepage discharge in Geo-Studio is 5.82 x 10-3 m3/s, compared to the manually calculated seepage discharge of 5.98 x 10-3 m3/s, resulting in a negligible difference of 2.672%, with a discharge difference of 0.00016 m3/s. The highest critical velocity occurs in rip-rap material and embankments at a height of 4.04 x 10-1 in the NWS modelling. The critical diameter limit for the most critical (smallest) material to be carried away is found in clay material with a critical diameter of 5.61.10-14 cm. The safety factor for suffusion symptoms indicates the most critical value in NWS modelling, with a value of 4.51. The seepage discharge is still within safe limits since the calculated discharge through the dam body is 0.062 m3/s less than the permitted discharge.