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p'. :_ 11:=- S ..- _- _'~_ _;FI:. iii F <br />t 7 <br />Table 4 Santa Fe ShQgr Strenoth RasUII$ <br />' fdaterlfll Friction Angle Cohesion gescriptlon <br />(degrees) (psi) <br />' Eollan 38.5 28 Trfaxlal -Intact <br />38.5 0 Trlaxiel- Post Shear <br />In addition, the slakabllity of the eollan was rated as high since k broke down into flakes attar two <br />minutes o1 testing. All laboratory results are found In Appendix IV. <br />4.0 SOUTH W LL DESIGN <br />' The strength parameters for the eollan material were employed for purposes of deslgh. It was <br /> observed to be the weakest and most abundant material wfthln the Santa Fe unit. Rotational; slope <br /> analysis was employed oil the south watt of the West Plt. Figure a shows the phreatlc surfecQ that <br />' would develop for the slope geometry Identi(led. Employing the tower bound design strengttjs (~ t <br /> 38.5 , c = 0 psq for the Sarrta Fe and the phreatlc surface shown In Figure 4 wll! result In a taptot of <br />' safety of 1.15. A value of 1.3 Is considered to be stable. The type of failure that results la an Iriflnke <br />slope or ravelling type which parallels the slope. This Is characterlstlc of coheslonless materials <br /> whose friction angle Is equNalent to the slope angle. The water table has minimal effect In this <br /> sftuatlon since the potential failure sudace Iles largely above the phreatlc surface, -rhe analysts I9 <br /> summarized In Appendix V. <br />1 <br /> <br /> <br /> <br /> <br /> <br />Employing 1 psi of cohesion will result In a factor of safety of 1.38. The design cohesion for the <br />Santa Fe material Is between 0 psi and 2B psi. <br />Tne above analysis is based upon observations from one drill section. D88-63 which Iles 94 feet to <br />the west is comprised of similar soil unRs to that Identified 6y the recent drilling. Halepaska <br />estimated that 125 gallons per minute of groundwater flow through the south wall oan be expected. <br />This Is dtscusaed In detail In Appendix III. This assumes that the field permeability fnr the alluvium Is <br />4 x 104 Cm~3eC. <br />Hole G 1 had showr. that gravel channels exist within the alluvium. It Is therefore Im fwrtant to <br />delineate the south wall for the presence of isolated flow channels. A test Cut along the south wall <br />will enable one to examine the materials prior to advancing the mining face to the nosh. This is <br />shown conceptually In Figure 5. The dimensions of the cut will be primarily a function of production <br />constraints. This method of mining should be continued beyond the alluvium antl into the Santa <br />Fe materials In order to monitor the behaviour and to optimize the design of the south wall. <br />The Inflow of water through the 10"r cmfsec material can be controlled by horizontaf dratne ddlled <br />along the base of the cut. The drains would be approximately 100 feet long and spae~ed 30 to:50 <br />i+ a <br /> <br />