Rock mass classification for design of excavation method and support system of tunnel 1 Sigli-Aceh toll road, Indonesia

Abstract

This paper presents an empirical design of the excavation method and the support system of tunnel 1 of the Sigli-Aceh toll road, Indonesia, based on the rock mass quality of Rock Mass Rating (RMR) and the Japan Society of Civil Engineers (JSCE). The results showed that the tunnel route consisted of fair to good quality calcarenite interlayered by sandstone and D II to C II rock categories based on the RMR and JSCE. Based on the RMR, recommended excavation method for the tunnel section having fair to good quality rock mass is the full-face, top heading and bench methods. The recommended support system is a rock bolt with a length of 3 - 4 m, spacing 1.5-2.5 m, shotcrete thickness 5 - 10 cm. Meanwhile, the recommended excavation method based on the JSCE classification with rock categories DII and CII is bench cut, and full-face methods with auxiliary bench cut. The recommended support system is a rock bolt with a length of 3 - 4 m, spacing 1.2 m, shotcrete thickness 10 - 20 cm, steel ribs H-125 -H-150, spacing 1-1.2 m, and lining 30 cm on the wall and 40 - 50 cm on the floor.