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Coal mine waste samples obtained by WESTEC from OXBOW wero tested in a laboratory <br />~~ contracted by WESTEC. A Standard Proctor compaction test (ASTM D-898) was parfom~ad <br />on s sample of the waste. The resuka wero used to remold another sample to 90 percent <br />compadlon, as the waste witl be placed in the waste bank, and direct shear tested using <br />ASTM D-3080: The resuhs wero a peak intemal angte•of-friction of 33 degrees, and a peak <br />cohesion of 2.0 kips per squaro toot (leaf). Based on the Standard Proctor test, a wet unit <br />weight of 91 pounds per cubic foot (pcf) was used with a saturated unit weight of 100 pd. <br />The coal mine waste is shown as material '1' on Figures 4.3 and 4.4. <br />Material properties fOr file cofkrvid sandstone above the Bowie Member shale underlaying the <br />sits was obtained using SPT bbweounts obtaned through the WESTEC borehole investigation. <br />At WBH-501, a 21 blows per foot measurement was recorded within the colluvial material. <br />Based on the depth, the blows were adjusted to 1 ton per square foot Itsf) overburden <br />according to procedures outlined by Peck, Hanson and Thombum (Peck et d., 1974). Ths <br />resulting corroded bbwcouM was related to an intend angle of friction of 33 degrees (Lambs <br />and Whitman, 19891. The material displayed non-cohesive characteristics in the field, so the <br />cohesion component of strerpth was modeled as 0 paf. Average unk weights for the material <br />was assumed to bs 115 pd wet, and 125 pcf saturated (Coduto, 19941. This colluvial <br />•' material is shown as material '2' in Figures 4.3 and 4.4. <br />•' <br />The Rollins Sandstone was proven a relatively strong, continuous strata through borehole <br />investigations and rock outcrop mapping. No previous failures have occurred in the aroa <br />invoh~ing the RolRna Sartdstorte and consuucdon of this magnitude founded diroctly on k. BY <br />historical records (Anderson, 1995), the Bowie MamberlRol(Ins Member interface is gently <br />dipping north, away from the toe of the cod mine waste bank. This is generally a favorable <br />situation, since then w~l be a natural tendency for resistance to movement abrp this <br />interface, ruling out this mode of failure. For these reasons, failuro within the Rollins <br />Sandstone Member was not selected ii a failuro mode for this stability anatysia. Rolins <br />Sandstone bebw the eke was modeled artifiaally high ao the computer program would rat <br />chose a fa8trs surface paseirq tfrotrgh as a aided fdhue sur'faee. Parameters chosen for the <br />sandstone were an internal angls•oRfrktlon of 50 degrees, a coheson of 5000 psf, and wet <br />and saturated unit weights of 150. The Rolins Sartdstane Member b identified as materiel '3' <br />on Figures 4.3 and 4.4. <br />96266/t424.RPT Cod MtM Wa~t~ e~Nc DNipn fa rfw 9~nbarn CrNt Mkr <br />oaoMr lase wESTtie, inc. <br />20 <br />