Rahardani, Rizal Undityo (2024) Analisis Modifikasi Lereng Tubuh Bendungan Terhadap Pengaruh Sensitivitas Rapid Drawdown, Gempa Dan Perubahan Muka Air Pada Bendungan Jragung Kabupaten Semarang. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Bendungan tipe urugan merupakan jenis bendungan yang paling umum untuk dikerjakan di Indonesia, dengan komposisi material yang mudah didapatkan dan relatif berbiaya lebih ekonomis. Akan tetapi terdapat hal-hal yang perlu diperhatikan dalam proses desain maupun konstruksinya, misalnya terkait stabilitas lereng tubuh bendungan. Permasalahan yang harus dipertimbangkan dalam faktor keamanan lereng bendungan adalah pada saat kondisi rapid drawdown, yaitu kondisi ketika muka air bendungan turun secara tiba-tiba. Terdapat 5 sesar aktif yang berdekatan dengan lokasi bendungan Jragung diantaranya, sesar Semarang, sesar Rawapening, sesar Merapi-Merbabu, sesar Pati, dan sesar Opak. Sehingga dalam penelitian ini dilakukan penelitian terhadap beberapa model simulasi perubahan kemiringan lereng terhadap pengaruh gempa dan saat kondisi rapid drawdown. Berdasarkan hasil kestabilan lereng nantinya dilakukan analisa sensitivitas berdasarkan perubahan kemiringan lereng terhadap kondisi saat pasca konstruksi, saat muka air pengoperasian waduk dan kondisi rapid drawdown. Pada penelitian ini akan menganalisis perubahan nilai faktor keamanan yang terjadi pada lereng tubuh Bendungan Jragung akibat peristiwa rapid drawdown dan kegempaan (OBE dan MDE) dengan menggunakan bantuan software perhitungan analisis rembesan dan stabilitas lereng. Terdapat tiga model yang digunakan yaitu Model Ke-1 penggunaan geometri sesuai DED (kemiringan lereng hulu 1 : 3,0 dan kemiringan lereng hilir 1 : 2,5), Model Ke-2 penggunaan modifikasi geometri kontruksi lapangan (kemiringan lereng hulu 1 : 2,5 dan kemiringan lereng hilir 1 : 2,5), Model Ke-3 penggunaan modifikasi geometri kontruksi lapangan (kemiringan lereng hulu 1 : 2,5 dan kemiringan lereng hilir 1 : 2,25). Dari ketiga model akan di proses tahap awal untuk mencari phreatic line pada tubuh bendungan ketika drawdown dan tahap selanjutnya untuk mencari nilai faktor keamanan lereng bendungan. Setelah dilakukan analisis keseluruhan baik dari sisi analisis rembesan maupun analisis stabilitas terhadap tiga model simulasi, untuk konstruksi dilapangan pada bendungan Jragung ini dapat menggunakan Model Ke-3, yaitu usulan modifikasi geometri dengan kemiringan lereng hulu 1 : 2,5 dan kemiringan lereng hilir 1 : 2,25, dan parameter material sesuai spesifikasi ketersediaan di lokasi pekerjaan. Terkait stabilitas lereng memenuhi dengan catatan pada saat beban gempa MDE 10.000 thn saat kondisi rapid-drawdown y/h =0,5h dan y/h=0,75h terdapat kemungkinan bendungan Jragung akan mengalami kerusakan, namun tidak roboh.
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Earth dams are the most common type of dam to be worked on in Indonesia, with a material composition that is easy to obtain and is relatively more economical. However, there are things that need to be considered in the design and construction process, for example, regarding the stability of the slope of the main dam. The problem that must be considered in the dam slope safety factor is during rapid drawdown conditions, namely conditions when the dam water level drops suddenly. There are five active faults adjacent to the Jragung dam location, including the Semarang fault, Rawapening fault, Merapi-Merbabu fault, Pati fault, and Opak fault. So in this research, research was carried out on several simulation models of changes in slope under the influence of earthquakes and during rapid drawdown conditions. Based on the slope stability results, a sensitivity analysis will be carried out based on changes in slope due to conditions during post-construction, when the water level is operating in the reservoir, and rapid drawdown conditions. This research will analyze changes in safety factor values that occur on the slopes of the Jragung Dam due to rapid drawdown and earthquake events (OBE and MDE) using the help of seepage and slope stability analysis calculation software. There are three models used, namely the 1st model using geometry according to DED (upstream slope 1: 3.0 and downstream slope 1: 2.5), the 2nd model using modified field construction geometry (upstream slope 1: 2.5 and downstream slope 1: 2.5), and the 3rd model using modified field construction geometry (upstream slope 1: 2.5 and downstream slope 1: 2.25). The three models will be process in the initial stage to find the phreatic line on the main dam during drawdown and in the next stage to find the safety factor value for the dam slope. After carrying out an overall analysis both in terms of seepage analysis and stability analysis of the three simulation models, for field construction of the Jragung Dam, the 3rd Model can be used, namely the proposed geometric modification with an upstream slope of 1:2.5 and a downstream slope of 1:2.25, and material parameters according to specifications available at the work site. Regarding slope stability, it is noted that during the MDE earthquake load of 10,000 years, during rapid-drawdown conditions y/h = 0.5h and y/h = 0.75h, there is a possibility that the Jragung dam will experience damage but will not collapse.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Bendungan Urugan, Stabilitas Lereng, Rapid Drawdown, Pengaruh Kemiringan, Gempa OBE, Gempa MDE, Phreatic Line, Earth Dam, Slope Stability, Rapid Drawdown, Slope Influence, OBE, MDE, Phreatic Line. |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA455.S6 Soil (Materials of engineering and construction) T Technology > TC Hydraulic engineering. Ocean engineering > TC167 Dams, reservoirs |
| Divisions: | Faculty of Civil Engineering and Planning > Civil Engineering > 22101-(S2) Master Thesis |
| Depositing User: | RIZAL UNDITYO RAHARDANI |
| Date Deposited: | 09 Aug 2024 02:45 |
| Last Modified: | 09 Aug 2024 02:45 |
| URI: | http://repository.its.ac.id/id/eprint/114520 |
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