Recommendations of excavation and support systems of Pamukkulu Dam diversion tunnel based on correlation of rock mass classification between RMR and GSI

This paper presents the results of geological engineering research conducted to determine character rock masses, recommendations tunnel excavation method and support system based on standup time estimates in unsuported conditions. The investigation was by observing mass quality newest bore log sample test 2019 using Rock Mass Rating (RMR) Geological Strength Index (GSI) classification. showed that area consist lithology form porphyryc lava basalt pyroclastic volcanic breccia. has a slightly weathering alteration rates. Intact rocks have Uniaxial Compressive (UCS) values ranging from 100-250 Mpa >250 are category strong rocks. fair good class III-II RMR between 53-69, GSI 48-64. roof span required is obtained planning 10 meter, with stand-up 70 hours without immediate collapse for 5 days. recommended methods drill blast top heading bench: 1,5-3 meter advance face, then can be bolts (20 mm diameter, fullly bonded): systematic 4 long, spaced 1,5-2 crown bench wiremesh shotcrete: 50-100 crown, 30 sides, steel ribs support.