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~~ <br />• MainCressonSlopeEvaluation AdrianBrown <br />4. Condition of joints. The condition of the joints in the rockmass is that they are in general <br />stained with iron oxide, and are either unfilled, or are cemented by the iron deposition. <br />Occasionally, joints are observed to contain clayey or gouge materials. The rock mass around <br />the joints is of good quality. <br />5. Groundwater. As noted in Section 4 above, the slopes at the Main Cresson Mine are dry. <br />Accordingly, there is no water pressure to reduce the stability of the slope. <br />6. Joint orientation adjustment. The joint orientation in the mine slope materials is favorable for <br />stability. There are very few joints which dip into the mine, and those which do are generally <br />not persistent over more than a single bench. However as there is some evidence of an <br />increasing trend of unfavorably dipping joints, the joint orientation classification selected for <br />this evaluation is "favorable", rather than "very favorable". <br />The quantitative CSIR evaluation for the East Wall of the South Mine (which is both the highest and the <br />steepest slope in the mine) is as shown in Table 9. <br />Table 9. CS/R Rock Mass Classification <br />• <br /> <br />Item Classification Parameter Value Rating <br />1 Strength of intact material UCS=120 MPa 12 <br />2 RQD RQD=70-95% 17 <br />3 Joint spacing Spacing=0.3 m 15 <br />4 Condition of joints Rough/hard wall rock 20 <br />5 Groundwater Dry 10 <br />6 Joint orientation adjustment Favorable -5 <br /> Total score 69 <br /> Rock mass classification Good rock II <br />7.1.2 Norwegian Geotechnical Institute Classification <br />A measure of the quality of the rock can be obtained using the Norwegian Geotechnical Institute (NGI) <br />classification method. In this, a similar suite of considerations are used to determine index values for the <br />significant parameters, and they are combined to produce a ranking. This is used for rockmass <br />characterization. The method is described in Hoek and Brown, 1980, pp. 27-34. The tabulation of the <br />values for the method is presented below in Table 10. Based on this finding, rock quality is between good <br />and very good. <br />1385D.98061 Z 39 <br />