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January 9, 1996 -3- 943-2847.001 <br />Interface Shear Strength Testing <br />The following configurations were tested with the laboratory test results presented in <br />Attachment A: <br />1. Cresson Ore Drain Cover Fill / 80 miI smooth LLDPE /Ironclad Soil Liner Fill. Test <br />results yielded a cohesion of 1235 psf. and friction angle of 26 degrees, fer both the <br />peak and residual values. The failure plane was noted to occur between the Soil Liner <br />Fill and the 80 mil smooth LLDPE geomembrane; <br />2. Cresson Ore Drain Cover FiII / 80 mil smooth LLDPE with 60 percent Carlton <br />tailings/Ironclad Soil Liner Fill. Interface testing performEd indicated peak and <br />residual values for the cohesion and friction angle to be 435 psf and 30 decrees, <br />respectively. The failure surface occurrec between the Soil Liner Fill and the 80 mil <br />smooth LLDPE geomembrane; <br />3. Cresson Ore Drain Cover Fill / 80 mil smooth HDPE /Ironclad Soil Liner Fill. The <br />material had a peak cohesion of 845 psf and a friction angle of 24 decrees, and a <br />residual cohesion of 895 psf and a friction angle of 23 degrees. The failure surface <br />was noted to occur between the Soil Liner Fill and the 80 mil smooch HDPE <br />geomembrane; <br />4. Cresson Ore Drain Cover Fill / 80 mil smooth HDPE with 60 percent Carlton tailings / <br />Ironclad Soil Liner. A peak friction angle of '?6 degrees and cohesion of 245 psf was <br />measured, in addition to a residual friction angle of 2S degrees and cohesion of 340 <br />psf. The failure plane was observed to occur between the Soil Liner Fill and the 80 <br />mil smooch HDPE geomembrane; <br />5. Cresson Ore Drain Cover Fill / 100 mil smooth HDPE /Pad iVa. 3 Low Volume <br />Solution Collection Fill. The material had a peak cohesion of 290 psf and a friction <br />angle of 30 degrees, and a residual cohesion of 275 psf and a friction angle of 29 <br />decrees. The failure surface was noted to occur between the Low Volume Solution <br />Collection Fill and the 100 mil smooth HDPE geomembrane; <br />6. Pad No. 3 Low Volume Solution Collection FiII / 100 mil smooch HDPE .Area `'o. 2 <br />Soil Liner Fill. The material had a peak and residual cohesion of 500 psf and a friction <br />angle of 7 degrees. The failure surface was noted to occur between the Soil Liner Fill <br />and the 100 mil smooch HDPE geomembrane; <br />7. Due to the results obtained from configuraeion 6, the configuration was modified to Pad <br />No. 3 Low Volume Solution Collection Fill / 100 mil textured HDPE /Area No. 2 <br />' -'' Soil Liner Fill (Sample No. TP-20). The material had a peak and residual cohesion of <br />2195 psf and a friction angle of 14 degrees. In addition, interface shear strength test <br />was repeated for the same configuration with the e.YCeption that Sample TP-1 was used <br />for the Soil Liner Fill. The test results for the second conf guration indicated the <br />Golder Associates <br />