Engineering Geological Characteristic Based On Rock Mass Rating (RMR) and Geological Strength Index (GSI) At Alternative-2 Feasibility Plan Of The Bodri Dam Diversion Tunnel, Kendal Regency

Quentino Elgar Pramarsantya (a,c), I Gde Budi Indrawan (b), Esti Handini (b)

Engineering Geological Characteristic Based On Rock Mass Rating (RMR) and Geological Strength Index (GSI) At Alternative-2 Feasibility Plan Of The Bodri Dam Diversion Tunnel, Kendal Regency
Quentino Elgar Pramarsantya (a,c), I Gde Budi Indrawan (b), Esti Handini (b)

a) Graduate Student in Underground Geological Structure, Departement of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia
b) Departement of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia
c) Ministry of Public Works an Housing, Jakarta, 12110

Abstract

Site characteristics develop a better understanding of geological conditions in purpose to prevent failure especially in tunnel construction planning. Bodri Dam with the diversion tunnel has feasibly planned by River Basin Organization for Pemali Juana of Ministry of Public Works and Housing in 2018. However, the detailed analysis for rock mass quality around the diversion tunnel siteplan has never carried out. This paper aims to identify the characteristics of the tunnel siteplan area through engineering geology, including morphological and lithological unit, geological structure, and geomechanics, which are rock mass characterization using Rock Mass Rating (RMR) and Geological Strength Index (GSI). The results from geological mapping indicated that the Bodri Dam diversion tunnel siteplan alternative-2 has two primarly lithologies, namely andesite breccia unit and tuffaceous sandstone unit. This tunnel is projected in rock mass with dominantly moderate rocks (rating 45-50) and poor rocks (rating 25-35) based on Rock Mass Rating method (Bieniawski, 1989). The rock structure type are identified as very blocky and blocky blocky and blocky with moderately weathered, highly weathered so that type of rock mass quality is fair and poor based on Geological Strength Index method (Hook and Brown, 1997). This results of characterization of the rock mass quality will influence the excavation method of diversion channel in Bodri Dam.

Keywords: geological engineering- rock mass rating- geological strength index- diversion tunnel planning- Bodri Dam

Topic: Hydrology, hydrogeology, and geology engineering