$2.$ A $6\mathrm{.}25$m diameter tunnel is to be driven in a hard and slightly folded rock mass of igneous origin. The rock mass is found to have a UCS of $249$MPa and RQD of $90\%.$ The tunnel axis will be parallel to the strike of the rock mass with a dip of $25$ deg Upon further investigation the rock mass has few joints that are tight, very rough and found to be discontinuous with an average spacing of $2\mathrm{.}5$ meters, the recorded water inflow per $10$m tunnel length is zero, and the rock mass has low stress fleld. The average joint spacing is three meters and the joint walls are unaltered and found to have surface staining only.

What would the Q value be and what supports would you recommend if the tunnel construction will push through

SOLUTION:

RQD$=$

J$\_\{$n$\}=$

Jr

Ja $=$

j$\_\{$W$\}=$

SRF$=$

RECOMMENDED SUPPORT: