Open AccessAnalysis of The Stability of Dam Building After Counterweight Additions (A Case Study: Gonggang Dam, Magetan Regency)
Author(s) -
P Kuntoro,
Niken Silmi Surjandari,
Rintis Hadiani
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/650/1/012024
Subject(s) - counterweight , safety factor , geotechnical engineering , stability (learning theory) , environmental science , seismic loading , factor of safety , geology , structural engineering , engineering , computer science , machine learning
The Gonggang Dam was first planned to be a rock filled dam, but due to the economic consideration, in the construction, the materials were changed from rock piles to random heaps with the fixed degree of slope. After being operated for a year with the observation on the possibility of seepage, no seepage was found. Therefore, to increase the stability of the dam body, a counterweight in the form of random pile completed with a filter and rip-rap was added to the lower part of the body of dam. The height of counterweight was determined based on the safety needs from the flow (surface) of the seepage line and the stability of the dam. The calculation results of stability analysis of the dam body with counterweights was considered effective as the downstream safety. Safety factors obtained from empty conditions, flood water levels and rapid drawdown without seismic load show the equation: security factor ≥1.2, which was in accordance to the permitted safety factor: sf ≥1.2. Meanwhile, the calculation result of the analysis of stability of the dam body with Operation Base Earthquake (OBE) and Maximum Design Earthquake (MDE) in empty condition and flood water level, the safety factors obtained were still above the permitted limit, ≥1.2. However, for rapid drawdown conditions with the effect of the MDE seismic load was not yet safe (collapse), so it was necessary to modify the design of the upstream leg section. The design modification was carried out by adding a random land fill structure that blends with the body of the main dam. The method was expected to be able to withstand the tension occurring upstream, thus increasing the stability of the dam body. This was proven to be effective based on the calculation results obtained by the safety factor of 1.115. The number was still included in the permitted Maximum Design Earthquake (MDE) safety number of load effect (sf ≥1).