ENGINEERING GEOLOGICAL STUDY TO DETERMINE EXCAVATION METHODS AND SUPPORT SYSTEMS IN ALTERNATIVE PLANNING 1 CONSTRUCTION OF THE BODRI DAM DIVERSION TUNNEL, KENDAL DISTRICT, CENTRAL JAVA PROVINCE
Kurnia Sandi Mahardhika (a), I Gde Budi Indrawan (b), Nugroho Imam Setiawan (c) (c

(a) Gadjah Mada University, Department of Geological Engineering, Yogyakarta, Indonesia
e-mail : kurniasandimahardhika[at]mail.ugm.ac.id
(b) Gadjah Mada University, Department of Geological Engineering, Yogyakarta, Indonesia
e-mail : igbindrawan[at]ugm.ac.id
(c) Gadjah Mada University, Department of Geological Engineering, Yogyakarta, Indonesia
e-mail : nugroho.setiawan[at]ugm.ac.id

Abstract

During dam construction, there are tunnels in the diversion channel which are very important to study technically. In 2018, the Organization River Basin of Pemali Juana carried out activities in the form of a feasibility study on the Bodri Dam. The feasibility study did not explain the excavation method and support system to be used in the Bodri Dam diversion tunnel. Based on this, this research examines the appropriate excavation methods and support systems to use based on the engineering geological characteristics that exist in the area around the Bodri Dam diversion tunnel alignment. The results of this research can provide input excavation methods and tunnel support systems for planning the construction of the Bodri Dam bypass tunnel on alternative route 1.
The research method used in this research is to carry out technical geological mapping in the area around the alternative Bodri Dam bypass tunnel alignment for primary data collection. Secondary data collection was carried out on drilling results from planning consultants at Organization River Basin of Pemali Juana. Laboratory tests were carried out on surface samples and drilling samples.
Determining the excavation method based on the excavability graph (Pettifer and Fokes, 1994) shows that the dominant excavation methods are easy digging and hard digging. Determining another excavation method to be used is based on the Rock Mass Rating (Bienawski, 1989), which shows that the appropriate excavation method results are by making a top heading and bench and installing supports along with excavation 10 m from the face of the excavation. Determination of the buffer system is divided into 3 areas, namely inlet, middle and outlet. The tunnel inlet outlet and middle require supports, namely shortcrete, rock bolts, wire mesh, steel sets, and fiber reinforced sprayed concrete.

Keywords: Engineering Geological, Excavation Method, Support System

Topic: Interdisciplinary Earth Science and Technology