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Y_rison-Knudsen C�-: Pane, Inc. <br /> October 25, 1977 <br /> Pale four <br /> According to the field density test results (see yu;;ust 8, 1977, ``K inter- <br /> office corres?on('_-nce in ?pt.ndix 2) , the mean dry density for tests <br /> within the up?er 1 foot of the dump was 80.6 lb/ft3, whereas tests tai:en <br /> 1n trenches at an average do?th of 12 f_et i-d_ -a ged a "':ran density of <br /> 82.0 lb/ft and a water content of 8. 0 ercent. Based on the field -and <br /> laboratory test results, the average fabricated density selected for <br /> triaxial and permeability testing was 80. 0 lb/ft3, which, on _he _asis <br /> Of data flit Shed L'S, c`_ = rS t0 rC _ It a :Cal- vely _J"v: u� =Tc�e <br /> relative density for the coal =cfL'Se. _'ater'_•at of '_y 40 <br /> Isotropically consolidated-drained (ICD) triaxial tests were performed on <br /> three fabricated samples of the coal refuse material, consolidated to <br /> pressures of 20.0, 40.0, and 80.0 psi. A sample diameter of 6 inches <br /> was selected, thus enabling the incorporation of 1-1/2-inch maximum <br /> particle size. The gradation of the tested samples was adjusted so that <br /> it matched the "as received" gradation on the 3/4-inch sieve. Therefore, <br /> the coarsest 18 percent (i.e. , plus 1-1/2-inch size) was excluded from <br /> the sample. It was not necessary, in our opinion, to perform larger <br /> diameter (say 12.0-inch-diameter) triaxial tests, because the fabricated <br /> 6-inch-diameter samples matched the "as received" gradation for over <br /> 70 percent of the finer-grained portion of the total sample. <br /> In addition to the three fabricated samples described above, one "stovepipe" <br /> sample obtained with the Dennison sampler appeared to be sufficiently un- <br /> disturbed to test. This sample was also tested under ICD test conditions <br /> at 40.0 psi in order to compare the results with those for one of the <br /> fabricated samples. The drained triaxial shear test results for the <br /> fabricated samples, presented on Figures 4 and 5, indicate an effective <br /> stress friction angle of 39.60 with zero cohesion. The single-point test <br /> for the one in-situ sample tested compares favorably with these results <br /> and, if considered separately, indicates an effective stress friction <br /> angle of 37.80 assuming zero cohesion. The stress-strain characteristics <br /> WA.,VVYIER <br /> & ASSOMTE <br />