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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-8106 <br />DATE: March 12, 2003 <br />A_? <br />DIVISION OF <br />MINERALS <br />GEOLOGY <br />RECLAMATION <br />MINING-SAFETY <br />Bill Owens <br />TO: Peter Wayland, Weiland Sugnet, Inc. Governor <br />Greg E. Walther <br />f? <br />FROM: Allen Sorenson Executive Director <br />Ronald W. Cattany <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 pcf <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 pcf <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 Documents\shear strength parameters.doc