Engineering Geology of Diversion Tunnel Area at the Meninting Dam Construction, West Lombok, Province of West Nusa Tenggara, Indonesia

https://doi.org/10.22146/jag.57293

Yunie Wiyasri(1), Anastasia Dewi Titisari(2*), Sia Pamela Dita(3), I Gde Budi Indrawan(4)

(1) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada
(2) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada
(3) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada
(4) Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada
(*) Corresponding Author

Abstract


The construction of Meninting Dam is undertaken to resolve the water needs in Meninting Watershed, West Lombok, Province of West Nusa Tenggara, Indonesia. Therefore, creating a diversion tunnel is imperative to avert the river flow as the dam project commences. Also, engineering geology work on the soil and rocks, including the classification of physical and mechanical properties were conducted in the intended tunnel site. These considerations were necessary because of the unavailability of rock identification data using the GSI (Geological Strength Index) method which used to design the portal slopes as a significant factor in tunnel safety. The results show the proposed area for diversion tunnel construction to be in the lithology of the polymict breccia and the lapilli tuff units, and the soil conditions were included in the SM category (silty sand). The level of surface rock weathering was divided into 3 units, including: highly weathered residual soil lapilli tuff, and highly, as well as moderately weathered polymict breccias. Meanwhile, 4 units were identified on the rock cores (subsurface) comprising highly weathered residual soil of lapilli tuff, and highly, moderately, and slightly weathered polymict breccias. Based on GSI (Geological Strength Index) of rock and surface data from the area of study, the rock quality was grouped as poor (GSI values: 21-40) to very poor (GSI values: 0-20). However, drilling data classified the mass quality subsurface rocks in fair (GSI values 41-55), poor (GSI values: 21-40), particularly in tunnels, and very poor (GSI values 0-20). Therefore, the rock mass quality is possibly used to design the slope of the tunnel portal as 45⁰-55⁰, in order to ensure safety.

Keywords


Meninting; Engineering Geology; lithology; soil classification; rock mass quality; GSI; tunnel portal slope

Full Text:

PDF


References

ASTM (2000). Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System). USA.

Anonymous (2013). Studi Kelayakan Bendungan Meninting Kabupaten Lombok Barat. Laporan Konsultan PT. (Persero) Indra Karya Wilayah I, BWS Nusa Tenggara I, Ditjen Sumber Daya Air, Kementerian Pekerjaan Umum dan Perumahan Rakyat, Mataram (not published).

Anonymous (2014). Detail Desain Bendungan Meninting di Kabupaten Lombok Barat. Laporan Akhir Konsultan PT. (Persero) Indra Karya Wilayah I, BWS Nusa Tenggara I, Ditjen Sumber Daya Air, Kementerian Pekerjaan Umum dan Perumahan Rakyat, Mataram (not published).

Anonymous (2016). Peta Genangan Bendungan Meninting Kabupaten Lombok Barat - Nusa Tenggara Barat. Pusat Bendungan, Ditjen Sumber Daya Air, Kementerian Pekerjaan Umum dan Perumahan Rakyat (not published).

Bieniawski, Z. T. (1989). Engineering Rock Mass Classification. Mining and Mineral Resources Research Institute. Pennsylvania State University. Fisher, R.V., 1966. Rocks composed of volcanic fragments and their classification. Earth-Science Reviews 1, 4, 287-298.

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

Hoek, E., & Brown, E. T. (1997). Practical estimates of rock mass strength. International Society for Rock Mechanics. International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts. 34(8), 1165-1186.

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

Hoek, E., & Karzulovic A. (2000). Rock Mass Properties for Surface Mines. In Slope Stability in Surface Mining, by W.A. Hustralid, M.K. McCarterand D.J.A. van Zyl, 59-70. Littleton, Colorado.

Mangga, S. A., Atmawinata, S., Hermanto, B., & Amin, T. C. (1994). Peta Geologi Regional Lembar Pulau Lombok, Nusa Tenggara Barat Skala 1:250.000. Pusat Penelitian dan Pengembangan Geologi, Bandung, 1 page.

Marinos, P., & Hoek, E. (2000). GSI: A Geologically Friendly Tool for Rock Mass Strength Estimation: Proceedings of GeoEng 2000 at The International Conference on Geotechnical and Geological Engineering, 1422–1446.

Singh B., & Goel R. K. (2011). Engineering Rock Mass Classification (Tunneling, Foundation, and Landslides), Elsevier Inc, United States of America.

Sivakugan, N., Shukla, S. K., & Das, B. M. (2013). Rock Mechanics an Introduction, Florida: CRCPress.

van Bemmelen, R.W. (1949). The Geology of Indonesia Vol. I A General Geology of Indonesia and Adjacent Archiplegoes. The Hague: Government Printing Office.



DOI: https://doi.org/10.22146/jag.57293

Article Metrics

Abstract views : 1187 | views : 1142

Refbacks

  • There are currently no refbacks.


Copyright (c) 2022 Yunie Wiyasri, Anastasia Dewi Titisari, Sia Pamela Dita, I Gde Budi Indrawan

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Journal of Applied Geology Indexed by:

 

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.