Laserfiche WebLink
t~ <br />~' <br />• <br />• <br />4.2 ROCK TUNNEL DISPOSAL FACILITY <br />An investigation similar to that at the coal refuse disposal <br />facility was performed at the site of the rock tunnel waste <br />disposal. The facility was visually inspected and a series of <br />compaction tests performed at the site on the same day. <br />The visual inspection confirms that the material of the dis- <br />posal facility has the character of a fairly good quality <br />rockfill. It consists mostly of gravel and larger size fragments <br />of Mancos Shale, with a very limited amount of fine fraction. It <br />is also evident that the fill has been built according to the <br />specification, i. e. the material was hauled to the site with <br />trucks and then spread in horizontal layers and compacted by <br />transporting equipment. Central portions of the facility have a <br />very good appearance and no signs of either stability or se*_tle- <br />ment problems. <br />The side slopes of the facility, however, carry frequent <br />signs of sliding, sloughing, or mudflows. According to the in- <br />formation obtained at the site, these surficial stability prob- <br />lems were caused by accidental removal of the uppermost waste <br />pile layer by dozers and by dumping this material over the crest. <br />Because of the probable presence of snow, the surface material <br />was close to saturated, and when pushed over the crest, it <br />created the surficial stability problems. <br />The compaction of the rock tunnel waste was verified by a <br />total of nine in situ tests. As in the previous case, two tests <br />were performed by the sand cone method, and the remaining tests <br />were carried out with the nuclear density device. Unlike at the <br />coal refuse disposal facility, the nuclear density device tests <br />provided apparently satisfactory results as no organic matter was <br />present within the waste -pile. <br />The results are presented in the Appendix of the report. The <br />laboratory moisture and density relationship on the same material <br />was performed and is also presented in the Appendix. Maximum dry <br />densities of 134.5 and 135.9 pcf were determined. The results of <br />the compaction testing indicate that compaction on the order of <br />90 $ or slightly less was achieved in most cases. An exception- <br />ally low compaction of 68 to 69 o was found at locations where a <br />locally increased moisture content was observed. Such locations <br />probably correspond to locations were snow was mixed with the <br />waste. <br />The results of Lincoln DeVore and recent testings show that <br />the maximum densities estimated in 1979 and at present coincide <br />very closely. While maximum densities of 131.2 pcf were obtained <br />by Lincoln DeVore, only slightly higher densities of 134.5 to <br />135.9 pcf were estimated at present. For this reason, it appears <br />that the results of Lincoln DeVore triaxial testing, performed on <br />18 <br />.r..:~,.~ _.... GEO#tY[)RQ:~tp!NSULTING.INC._ <br />