Laserfiche WebLink
_IZ_ <br />Characteristics of Materials <br />The characteristics of the spoil fill material were estimated .from <br />observation of performance of existing spoil piles, review of various reports <br />performed for The Colowyo Coal Company, our experience with spoil <br />generated from similar overburden materials in other areas of Routt and <br />Moffat Counties, and published data regarding strength characteristics of <br />rock fills. In our opinion, the fill will function essentially as a granular <br />material. We used an angle of internal friction in the range of 35 to 39 <br />degrees. No cohesion was assumed to occur in The spoil. <br />The stiff to very stiff clays found in our borings at The valley bottom <br />were tested using Triaxial strength tests and unconfined compressive strength <br />tests. The unconfined compressive strength tests indicated cohesion of about <br />3,000 psf; this represents undrained shear strength. A Triaxial strength Test <br />performed using aconsolidated-undrained test procedure with pore pressure <br />measurements indicoted drained shear strength of 500 psf and a friction angle <br />of I S° for the clay. <br />We assumed The underlying bedrock found below the valley bottom and <br />near the surface on the slopes of the spoil area To have o cohesion intercept <br />of 5,000 psf and no friction. This is likely a conservative estimate of The <br />actual shear strength of the bedrock. <br />Drainage Conditions <br />Performance of any fill, or natural slope, is highly influenced by the <br />location of the free water surface which develops in the slope. Diversion of <br />surface drainage around the spoil will limit the amount of water entering the <br />e <br />