Stability Analysis of Saka DAM Diversion Tunnel Portal

Febrie Maulana Fajrin; Subagyo Pramumijoyo; I Gde Budi Indrawan

doi:10.22146/jag.57578

Stability Analysis of Saka DAM Diversion Tunnel Portal

https://doi.org/10.22146/jag.57578

Febrie Maulana Fajrin⁽¹⁾, Subagyo Pramumijoyo^(2*), I Gde Budi Indrawan⁽³⁾

(1) Balai Besar Pelaksanaan Jalan Nasional Sumatera Selatan, Ditjen Bina Marga, Kementerian PUPR
(2) Geological Engineering Departement, Universitas Gadjah Mada
(3) Geological Engineering Departement, Universitas Gadjah Mada
(*) Corresponding Author

Abstract

The Saka Dam has a channel in the form of a diversion tunnel. This paper presents the results of rock mass characterization using the Geological Strength Index (GSI) classification and evaluation of the stability of the tunnel portal slope with earthquake loads using numerical methods. Based on the GSI classification, the Saka Dam tunnel portal slope is composed of rock masses that are poor quality, fair, and good. The calculation results show the Saka Dam can experience earthquake loads with an acceleration value of 0.4g. Earthquake loads can cause a decrease in the safety value (SRF) of the tunnel portal slope based on the results of numerical analysis. SRF value of natural portal slope without earthquake effect is 10.23 (inlet) and 1.5 (outlet). SRF value of the design slope portal without earthquake effect is 6.64 (inlet) and 1.76 (outlet), whereas if the earthquake effect is taken into account the SRF value obtained is 20.31 (inlet) and 0.99 (outlet). This shows that the condition of the natural portal slope and the portal slope design planner section of the Saka Dam inlet diversion tunnel is in the safe category. Meanwhile, for the portal slope excavated from the outlet section, modification is needed to obtain a safe slope condition. The results of the modified geometry of the slopes at the outlet section resulted in an SRF value of 1.47 which indicates the slope is stable

Keywords

Saka, GSI, Slope stability

Full Text:

PDF

References

Anonim (2016). Laporan Utama Perencanaan Bendungan Saka Gilas. Palembang: PT. Global Parasindo Jaya.

BSN (2017). SNI (Standar Nasional Indonesia) 8460: Persyaratan Perancangan Geoteknik. Jakarta.

Dinata (2019). Evaluasi Kestabilan Lereng Portal Terowongan Saluran Pengelak di Bendungan Pasuruhan, Jawa Tengah. Yogyakarta. Geological Engineering Department, Gadjah Mada University.

Gafoer, T.C. Amin, & Pardede, R. (1993). Peta Geologi Lembar Baturaja. Bandung: Pusat Penelitian dan Pengembangan Geologi. National Earthquake

Research Centre. 2017. Peta Sumber Bahaya dan Gempa Indonesia. Jakarta. Kementerian Pekerjaan Umum dan Perumahan Rakyat.

Hoek, E., & Marinos, P. (2007). A Brief History of The Development of The Hoek-Brown Failure Criterion. Soils and Rocks No.2.

Hoek, E., Carter, T.G., & Diederichs, M.S. (2013). Quantiﬁcation of the Geological Strength Index Chart. The 47th US Rock Mechanics/Geomechanics Symposium. San Francisco, CA, USA: ARMA, American Rock Mechanics Association.

ISRM (1978). Suggested Methods for The Quantitative Description of Discontinuities in Rock Masses. Int. J. Rock Mech, Sci. & Geomech: 368.

Nuryanto (2017). Analisis Stabilitas Lereng dengan Metode Kesetimbangan Batas (Limit Equilibrium) dan Elemen Hingga (Finite Element). Depok: Civil Engineering Faculty and Planning, Gunadarma University.

Ramadhani (2019). Kestabilan Lereng dan Terowongan Batuan Metamorf Pada Tambang Emas Poboya di Palu Provinsi Sulawesi Tengah. Yogyakarta: Geological Engineering Department, Gadjah Mada University.

Sunardi (2019). Evaluasi Kondisi Geologi Teknik untuk Kestabilan Lereng Portal Terowongan Saluran Pengelak di Bendungan Leuwikeris, Ciamis, Jawa Barat. Yogyakarta: Geological Engineering Department, Gadjah Mada University.

DOI: https://doi.org/10.22146/jag.57578