Desain Alternatif Terowongan Pengelak Dan Terowongan Intake Bendungan Jragung

Rifai, Muhammad Nur (2026) Desain Alternatif Terowongan Pengelak Dan Terowongan Intake Bendungan Jragung. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Bendungan Jragung nantinya akan menyuplai air untuk daerah irigasi seluas 4,528 hektare di Kabupaten Semarang. Dalam perencanaan pembuatan bendungan ada faktor penting yang harus dipertimbangkan agar pekerjaan bisa berjalan dengan lancar yaitu sistem pengelak. Terowongan pengelak adalah salah satu sistem pengelak yang dibangun untuk mengelakkan aliran air sungai agar memudahkan dalam proses pengerjaan bangunan utama (tubuh bendung). Oleh karena itu, diperlukan perencanaan desain terowongan yang mencakup analisis hidrologi, analisis stabilitas, analisis faktor keamanan serta perhitungan penulangan struktur agar terowongan dapat berfungsi dengan aman. Perencanaan desain alternatif terowongan pengelak ini dibantu dengan perangkat lunak Plaxis 2D v.20 yang dapat memberikan pendekatan perhitungan yang lebih canggih dalam menganalisis kontruksi terowongan. Pada terowongan pengelak dan terowongan intake Bendungan Jragung direncanakan dimensi terowongan berbentuk tapal kuda, yang mana elevasi dasar inlet terowongan +60 dengan panjang 380 m. Pada proyek akhir ini, dilakukan analisis penelusuran banjir dengan menggunakan debit banjir periode ulang 25 tahun yang memiliki debit puncak sebesar 265,58 m³/dt dan didapatkan diameter penampang terowongan sebesar 4 meter dengan tinggi air maksimum pada elevasi +80,604. Sedangkan, dimensi terowongan intake didapatkan sebesar 2,15 m, karena telah memenuhi kebutuhan hidrolik, operasional dan maintenance. Analisis stabilitas berdasarkan tekanan menunjukan bahwa tekanan vertikal yang bekerja sebesar 58,312 t/m² lebih kecil daripada daya dukung massa batuan sebesar 162,210 t/m², sehingga terowongan dikatakan stabil. Analisis numerik mengggunakan plaxis 2D dilakukan pada dua kondisi, yaitu setelah kontruksi dan saat beroperasi dengan mempertimbangkan beban gempa. Dari hasil analisis plaxis 2D pada dua kondisi didapatkan nilai deformasi yang terjadi pada terowongan kurang dari 1% diameter sehingga deformasi yang terjadi masih berada pada batas izin. Nilai total displacement, horizontal displacement, dan vertical displacement utuk masing-masing kondisi menunjukan nilai deformasi kurang dari 40 mm. Dari hasil analisis plaxis juga didapat nilai faktor keamanan yang melebihi syarat faktor keamanan suatu kontruksi dapat dikatakan aman yaitu ≥ 1,5. Perencanaan struktur beton bertulang dilakukan menggunakan momen maksimum sebesar 208,0 kN/m yang diperoleh dari hasil analisis Plaxis 2D. Berdasarkan hasil perhitungan penulangan, diperoleh tulangan utama berdiameter D25 dengan jarak 250 mm (D25-250) dan tulangan bagi berdiameter D13 dengan jarak 110 mm (D13-110).
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Jragung dam will supply irrigation water to an area of 4,528 hectares in Semarang Regency. In dam construction planning, one of the important factors that must be considered to ensure the construction process runs smoothly is the diversion system. A diversion tunnel is one of the diversion systems constructed to divert the river flow and facilitate the construction of the main dam structure. Therefore, tunnel design planning should include hydrological analysis, stability analysis, safety factor analysis, and reinforcement design to ensure that the tunnel can function safely. The alternative design of the diversion tunnel was analyzed using Plaxis 2D V20, which provides a more advanced computational approach for tunnel construction analysis. The diversion tunnel and intake tunnel of Jragung Dam were designed with a horseshoe-shaped cross-section, an inlet invert elevation of +60 m, and a tunnel length of 380 m. In this study, flood routing analysis was carried out using the 25-year return period flood discharge with a peak discharge of 265,58 m³/s. The results indicated that the required tunnel diameter was 4 m, with the maximum water level reaching Elevation +80,604 m. Furthermore, an intake tunnel diameter of 2,15 m was selected because it satisfies the hydraulic, operational, and maintenance requirements. The tunnel stability analysis based on pressure showed that the applied vertical pressure of 58,312 t/m² was lower than the rock mass bearing capacity of 162,210 t/m², indicating that the tunnel was stable. Numerical analysis using Plaxis 2D was conducted under two conditions, namely after construction and during operation considering seismic loading. The results showed that the tunnel deformation under both conditions was less than 1% of the tunnel diameter, indicating that the deformation remained within the allowable limit. The total displacement, horizontal displacement, and vertical displacement obtained from the Plaxis analysis for both conditions were all less than 40 mm. In addition, the safety factor obtained from the Plaxis analysis exceeded the minimum requirement for a safe structure, which is SF ≥ 1,5. The reinforced concrete lining was designed using the maximum bending moment of 208,0 kN/m obtained from the Plaxis 2D analysis. Based on the reinforcement design, the main reinforcement consists of D25 bars spaced at 250 mm (D25-250), while the distribution reinforcement consists of D13 bars spaced at 110 mm (D13-110).

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Terowongan Pengelak, Q25, Dimensi, Stabilitas, Deformasi, Faktor Keamanan, Beton Bertulang, Diversion Tunnel, Q25, Dimension, Stability, Deformation, Safety Factor, Reinforced Concrete Lining.
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC167 Dams, reservoirs
Divisions:	Faculty of Vocational > 22301-Civil Infrastructure Engineering (D4)
Depositing User:	Muhammad Nur Rifai
Date Deposited:	04 Aug 2026 08:29
Last Modified:	04 Aug 2026 08:29
URI:	http://repository.its.ac.id/id/eprint/143612

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