Laserfiche WebLink
<br />Memo to Dave Berry <br />Bowie No. 2 Gob Pile Laboratory Testing <br />page 3 <br /> <br />penetration sampling, using procedures outlined by Peck, et. al. (1974) and <br />Lambe & Whitman (1969), to deduce shear strength parameters (internal angle <br />of friction and cohesion) for the completion of their stability analyses. In my <br />experience, blow count conversions can be suspect when penetration testing is <br />performed on materials containing large fractions of competent cobbles which <br />resist penetration. Maxim, having completed an entailed 23 bore augering <br />program and sampling of the materials, chose to perform four triaxial shear <br />tests of the "Lean Clay with Gravel". Maxim's test results determined that at <br />least two different material characters are manifested by this colluvial <br />material, depending largely upon its clay constituency and degree of hydration. <br />Undrained, unconsolidated triaxial compression tests performed on lower <br />plasticity materials had an angle of internal friction of 23° and an apparent <br />cohesion intercept of 2,200 psf. However, higher plasticity materials displayed <br />friction angles as low as 4° with an apparent cohesion of 3,050 psf. <br />Materials with strengths similar to these highly plastic colluvial Lean Clays <br />with Gravel will not result in acceptable SSF for the proposed refuse pile. <br />Therefore, the Division continued to request additional information to verify <br />WESTEC's assumed strength parameters for the "colluvial sandstone above the <br />Mancos Shale". <br />MAXIM's Laboratory Determinations <br />In response to our continued request, BRL directed MAXIM to complete analysis <br />of the materials in question. During subsurface exploration in August of 1996, <br />MAXIM drilled two shallow exploration holes, borings 27 and 28, within the <br />waste pile footprint for the purpose of sampling the materials for laboratory <br />analysis. MAXIM sampled the materials using a lined, modified California split- <br />spoon sampler. MAXIM's subsequently completed laboratory analyses to <br />determine the shear strength properties for the slope colluvial material, the <br />manmade fill, and the Mancos Shale. Test results determined the colluvial <br />material to have an angle of internal friction of 32° and a cohesion of 900 psf. <br />The manmade fill yielded an angle of internal friction of 36° and a cohesion of <br />200 psf. The medium hard to hard Mancos Shale sample was determined to have <br />