Abstract
Empirical design of support system at the Tunnel 6 of the Jakarta – Bandung high-speed railway was based on the Basic Quality (BQ) system, which had not been adopted in Indonesia. This research was carried out to better understand the rock mass quality at the tunnel construction site by comparing rock mass quality determined by the BQ system to that determined by two more popular rock mass classifications, namely the Geological Strength Index (GSI) and Rock Mass Rating (RMR). Surface and subsurface engineering geological mapping were carried out and tunnel excavation method and support system were proposed. The engineering geological model of the BQ, GSI, and RMR systems showed that the sedimentary rock masses of the Miocene Jatiluhur Formation generally had poor to very poor quality, while those of the Quaternary Volcanic Formation had very poor to good quality. Based on the RMR, the stand-up time values of the sedimentary rock masses were predicted to be relatively low as compared with those of the Quaternary Volcanic Formation, implying requirement of a relatively quick support system installation after excavation. In general, a combination of systematic bolt, shotcrete and steel ribs is the recommended support system for this tunnel.
Highlights
Tunnel 6 is the longest of the 13 tunnels of the JakartaBandung high-speed railway
The type of data is divided into 2 data models, surface data and subsurface data, both of which serve as variables in forming geological models, classification of rock mass quality, engineering geological models and empirical references to determine the initial design of the tunnel support system, standup time and determining the excavation method that will be used in the construction of the tunnel 6
Empirical support system design based on Rock Mass Ratting (RMR) for very poor-poor rock mass quality is a combination of rockbolt, shotcrete and steel sets, while for rock mass conditions fair-good steel sets are not required (Table 3)
Summary
Tunnel 6 is the longest of the 13 tunnels of the JakartaBandung high-speed railway. Tunnel 6 stretches for 4.4 km and crosses the administrative area of West Java Province: Purwakarta Regency on the inlet side and West Bandung Regency on the outlet side (Fig. 1). The angular unconformity relationship between the two formations at the study area shows the complexity of the geological conditions so that accuracy is needed to develop geological and engineering geological models in this work. This condition becomes more complicated where the lateral distribution of the rock on the surface is volcanic from Qob Formation, while at the elevation of the tunnel It is a fine-grained clastic sedimentary rock from the Jatiluhur Formation which is very limited exposed on the surface
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