We have a problem to be solved : A new copper mine is to be started-up. A 60m wide orebody outcrops on surface and dips at 85 degree towards the south. The orebody is economic up to 200m below surface. From 200m further deep the grades are very poor. Open pit has a limit of 150m. below that an underground mine has to take over. Underground equipment will include LHD's, drill rigs, some of which are at most 4m wide and 5m high. A representative log of the host rock is shown. Given that: 3 joints sets are prevalent this environment. The joints are mostly curved and slicken- sided, with some fine material infilling. Joint sets: J1 J2 J3 Dip (degrees): 78, 60,70 Dip direction (degrees): 110, 300, 70 Ave. Joint spacing: 1m, 0.6m, 0.3m RQD = 60 The host rock is slightly moist and wet in some locations K ratio = 1.6 Standard safety factor for the mine is 1.3 as a matter of policy (be it dumps, slopes, underground support, etc.). A company has requested you to perform a geotechnical design feasibility. That means: Now answer PART A Work out rock mass ratings. Determine stable slope angles Determine