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SLDF'E STABILITY RlVALYSIS -- fiIENAlJ # 2 MIPJE RACY-:FILLED 5LDAES • Samples of material from the existing mine bench were obtained from the site in late June, 1986. This material will be !tsed as the fill for the portal area. It is comprised of clay, sand, gra•sel and cooly material. This material was submi±ted tc Fv:; and Associates of Colorado far strength testing. The resu'_ts are enclosed. A clay benchfill was also analyzed, however, the amount of this material available for backfilling is not significant. The following parameters are relevant tc the analysis for the fill material: Ma;;imum dry density: i0._.5 lb./c!i. ft. Density used in anal•/sis: 88 lb.fcu. ft. Angle of friction (ma:;?: '0.5 degrees Angle of frictinn in analysis: ~7 degrees Cohesion (max): .°,80 lb./sq. ft. Cohesion used in analysis: 2~0 lb.;sq, ft. The numbers used in the analysis are significantly lever than the lab values because the direct shear tests were performed at 9~:": of the Modified F•roctor Density and only OS% can be e:;pected at slopes of ~H:IV. Also, the lab val!ies are ma::imums, and should be reduced for average fill values. • The REAME program for slope stability analysis developed by 'ra.ng H. Huang of the University of t;entucb:y is used ;n determining the slope safety factors with and without seepage. There are no springs or seeps in the area and it is felt that if the diversion is left intact, virtually no seepage will vcc!;!• because the diversion will carry all snowmelt and rain ~-:noff away from the embankment. The enclosed cross-section shows the backfilled area, the existing slope and the diversion. Sci'_ ? is the fill described above. Soil 1 is the material lying below the fill area. This material has a larger ame!tnt of clay and roc{: and will provide better strength. In'piace density tests performed with a Troxler '411-8 nuclear backacatter have shown an average density of 11~l lb/cu.ft. Estimates of the cohesion and internal angle of friction were made from Table '.1 of Dr. Hua.r:g Stability Analysis of Earth Slopes. Cohesion used in analysis: 300 lbisq. ft. Angle of friction used: ~0 degrees. The enclosed Case # 1 is the case without seepage (ass!;mina :,h•; diversion is left intact.? The minimum factor of safety is 1.61 and occurs at point (<U1.25, 7140._:') with a radius of ~._,?°~ ft. • ~/6/~~