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1 LJ 1 1 is after Hoek (1982). Table 6 and 7 summarize the individual design sets for the West and East Ore Zone respectively. Tha most critical joint set or combination of sets results in an east -west joint population that dips moderately (36°) to the south. This is identified in terms of critical wedges in the West Pit and by planar instability in the East Pit (fable 6 and 7). This structure is continuous as recorded through cell mapping (East Pit) and is generally 50 - 100 ft. in length. This dictates that all slopes whose dip direction is towards the south be designed so as not to undercut this structure. 7.2 Rock Mass Design Rotational slope analysis was employed in order to develop a design for the Santa Fe, Pink Gneiss and Green Clay materials. The 'simplified Bishops Method' of analysis was employed and the relationship between slope height and slope angle was determined using a factor of safety of 1.3 under dry conditions. The shear strength design parameters were based upon results obtained from laboratory testing (fable 4) and SRMR derived strengths (fable 5). Design curves relating slope height to slrope angle at a factor of safety of 1.3 are shown in Figure 15. The design SRMR curves as determined from Table 5 were employed. The remoulded strength curve for the samples tested have been :superimposed upon the design curves. The remoulded strengths are the lower bound as discussed in 6.3.1 whereas the SRMR design curves represent the average rock mass strength for the overall slope. The SRMR (Robertson, 1987) identifies three rock classes within the range of very weak rock. They are as follows: OVERALL ROCK MORE THAN MORE THAN MORE THAN MASS CLASS 50% LESS THAN 25% LESS THAN 12% LESS THAN SRMR = 41 SRMR = 31 SRMR = 21 5-20 YES YES YES 20-30 YES YES NO 30-40 YES NO NO OVER 40 NO NO NO Referring to Figure 16, a fifteen foot zone having over 509'0 (greater than 7.5 ft.) of SRMR = 41 material and more than 25% (greater than 3.8 ft.) of SRMR = 31 but less than 12% (les:c than 1.8 ft.) of SRMR = 21 would have an overall rating of 20 - 30. Table 8 summarizes the extent of poor material (SRMR < 20) incurred within the oriented drill core.