Engineering Geological Assessment of Diversion Tunnel of Bakhtiari Damsite (Biggest Two-Arch Concrete Dam in Southern Iran)

Table 6

Range of RMR values and description of the rock-mass class [5].

RMR	81–100	61–80	41–60	21–40	<20
Rock-mass class	I	II	III	IV	V
Description	Very good	Good	Fair	Poor	Very poor