SEEPAGE STUDY FOR DAM SAFETY

• Main Author: Karmila, Eulis
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/44096
• Institution: Institut Teknologi Bandung

The causes of dam failure are overtopping, slope instability and internal erosion, 38% of which is due to reed erosion (ICOLD Bulletin 109, 1997). Reed erosion results in a decrease in water flow resistance and an increase in hydraulic gradient. When the flow velocity increases as a result of the reduction in flow resistance which gradually decreases, granular erosion will occur further, forming piping that can cause collapse in the body of the dam. Therefore a study to overcome the seepage in the dam by creating an effective and efficient dam design through sensitivity analysis is needed to prevent dam collapse from reed erosion. Preventive action is carried out on two conditions chosen namely, the widening of the toe of dam core and installation of drainage filters on the upstream and downstream side of the dam core to overcome seepage in the dam body and the use of curtain grouting to overcome seepage on the foundation which is then controlled by the safety factor at the foot of the foundation as a location critical gradient. The results of seepage analysis and sensitivity are derived from the finite element method of GGU-SS FLOW2D Version 7. The results of seepage analysis and sensitivity show that the determinants of dam safety from seepage hazards are dam body geometry (core width and filter thickness), permeability of embankment and foundation material, water level, and securing the foundation (grouting depth). Seepage treatment on the dam body can be done by combining foot width (core slope of the dam) with a filter thickness where the analysis results are as follows: for a foot width of 0.5 H, a filter thickness with a transition of 6m, for a foot width of 0.7H, a filter thickness with a transition of 4m, and for ease of implementation, thick filter must be used with a transition of 6 m (3 m filter and 3 m transition). Seepage treatment on the foundation with permeability of (k) ? 10-4 cm/s can use curtain grouting. For dams with a height of> 100m, a minimum grouting as deep as 0.7H is required, whereas for dams with a height of <100m, a minimum grouting as deep as 0.5H is required. Seepage treatment for foundations with a foundation permeability coefficient between order 10-5 cm/s <k <10-4 cm/s requires grouting as deep as H (where H is the height of the dam). Seepage for foundations with k ? 10-5 cm/s can use other treatment such as cutoff wall.