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DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 D I V I S I O N OF <br />Phone: (303) 866 -3567 MINERALS <br />FAX: (303) 832 -8106 & <br />GEOLOGY <br />RECLAMATION <br />DATE: March 12, 2003 M I N I N .-SAFETY <br />TO: Peter Wayland, Weiland Sugnet, c. Go °ernor 5 <br />In <br />Greg E. Walther <br />FROM: Allen Sorenson Executive Director <br />Ronald W. Canany <br />Division Director <br />RE. Suggested Conservative Soil Shear Strength Parameters for Stability Analyses <br />Given that these strength values, in particular the residual strength value for the weathered bedrock, <br />represent the worst -case for potential slope instability, any safety factor in excess of one should be <br />protective of critical structures. <br />CLAY, sandy, soft to stiff, very moist to wet, brown (CL): <br />0' = 28 degrees c' = 50 psf moist unit weight= 114 pcf saturated unit weight= 126 pef <br />SAND, fine grained, clayey, silty, very loose, very moist to wet, brown (SC, SM): <br />0' = 25 degrees c' = 10 psf. moist unit weight= 90 pcf saturated unit weight= 115 pcf <br />SAND, fine grained, clean to slightly silty, dense, wet, brown (SP, SP -SM): <br />0' = 31 degrees c' = 0 psf moist unit weight= 117 pcf saturated unit weight= 130 pef <br />SAND & GRAVEL, fine to coarse grained, some cobbles, clean to slightly silty, very dense, wet <br />brown (SP, GP): <br />0' = 35 degrees c' = 0 psf moist unit weight = 130 pcf saturated unit weight = 137 pcf <br />WEATHERED SHALE, this is an over - consolidated stiff - fissured clay, so the residual strength <br />values are appropriate to the analysis: <br />0' = 14 degrees c' = 0 psf moist unit weight = 125 pcf saturated unit weight = 142 pcf <br />c:\acs\My DocumentAshear strength pararrx=rs.doc <br />