EVALUATION OF GEROKGAK DAM’S SAFETY STRUCTURE, BALI PROVINCE TO SUPPORT THE SUSTAINABILITY OF WATER RESOURCES INFRASTRUCTURE PURPOSE

• Main Author: DWI KHURTUMI NIM : 95015315, NOFYAR
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/29701
• Institution: Institut Teknologi Bandung

The purpose and capacity of the existing reservoirs can be guaranteed if the safety of the dam structure always ready for the latest loading conditions. One of them is through the evaluation of the dam structure safety to determine its safety status, which must be implemented at least once in five years. During ±17 years in operating, the structural evaluation of the Gerokgak Dam had been done once at 2012 with "sufficient" status. The dam can be operated as usual but not safe enough in flood and earthquake design. It was due to the design flood (HSS Nakayasu) calculated from from the rainfall data of 1985~2004 the freeboard on QPMF (1,10 m>0,75 m), discharge and seepage rate (0,12 l/s <0,20 l; 0,0024 m/s<Vcr 0,00282 m/s), safety factor (SF) to piping (2,266>2), maximum deformation (Swais Good method) in MDE (kh=0,431) which is referring to Indonesian Earthquake Map 2004 still meets the requirements (0,17 m), but the pseudo-static stability of the limit equilibrium method (Bishop Method) in the OBE (kh=0.254) some conditions did not meet the requirements. <br /> <br /> Along with the addition of rainfall data and Indonesian Earthquake Map 2010 and 2017, the dam structure needs to be re-evaluated. The result of design flood evaluation (HSS Snyder-Alexeyev) calculated from rainfall data of 1992~2015 the freeboard at QPMF (1,137 m), discharge and seepage rate (1,02 l/s < 3,30 l/s; 2,315x10-6 m/s<Vcr 0,00282 m/s), SF to piping (4,533>4), pseudo-static stability in OBE which is referring to Indonesian Earthquake Map 2010 (kh=0,10) and 2017 (kh=0,15) require to meet all the conditions (Method of Morgenstern-Price, Spencer, Bishop, and Janbu), as well as the maximum deformation (makdisi and Seed method) sequence to the MDE (kh=0,60) between 0,25~0,70 m, so the safety status becomes "good" and the dam can be operated as usual. There is no dam deficiency at this time or at any conditions that will happen. <br />