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r I. '' I ~,. I ~'.. r ST~'E OTC-~_CG-~J o.._ccC:-:vv G:•. rr 1. ~ I: i, .; r ~ ~/.J ~ia j • DEr'l FT:.!ENT OF N.GT U.RAL RESOURCES ~: i' ~•'-',~~ ~~ •' `!~~~ .•-~ `` e-~ D. Monte Fascoe Exew:we D~reC:or ~ , (' ~ F• r;; ~j- a =, .- ~iL'~ED LA.~D RECL~:~i~TIOY-- •. '~"'' -~ 3' ~.: `~ <23 Centenn~ai Bu~ld~ng, t3t3 Sherman Stree: -"-'~-~!~ Denver, Colorado 80203 Tel. (303) bob-3567 ~~ David C. Shelton • Director January 14, 1982 TO: lfike Savage \`\ FROr~f: Jim Pendleton ~' R5: Overburde. ~~~-__ Factor at the Trapper !fine Utah InternationaI's staff has presented a calculation of overburden s::e21 based upon surveyed pit volume divided by the number of dra cline s:,•ings (buckets). .:ssu.~nc correct determination of excavated pit volumes and the number of buckets reouired to excavate the pit, t'te operator should be correct in determining tie averaee in-place (bans: cuvic yardaoa) volu:•~ o_` the o:erburden excavated per buc.~:et. The operator then suggests that in-?lace excavated volume per Bucket d:i•ided into the rated thirty cubic yard capacity of the dragline bucket should r_=present the average overburden screll factor. This supposition would be acceptable if the applicant's assumption that the averaoe bucket contains thirty less cubic yards of overburden was verified, and if the applicant included consideration of consolidation of bacl:filled spoi I . The excavating capability of a draeline varies with the type of material being excavated and the ceometry of the pit. Variations in material type imply variation in fracmented par ti cal size.overburden density and resistance to buc}:et penetration, resulting in variations in the decree of fullness of the bucket. Variations in pit geometry affect ;he an~le bet:+een the cutting plane of the bucket and the came applying the cutting force. The greater the angle between the applied cutting force and the actual plane of cutting, the less the applied cutting force. Tine less the applied cuttinc force, ;1te less efficient the dragline Fill be, possibly result_'nc in an incompletely filled bucket. Utah internationa_''s contention appears to be that the geo~stry of their nits are such trat all o_` these factors balance one another and in she long run the average volume of overburden contained c.•ithir. each buc}:et ecuals the "rated struck. buc}:et capacity" of 30 loose cubic cards. In an e_°fort to ascertain the va1'dity of this assumption, S have contacted several ranu_`acturers of dra=lines and draeline but}:ets, and discussed with each the topic of but%:et ratinos and erca:-ational ef- ficiency. Contact was made with tec:nnical representatives for !?arior., Znc., r^aee Engineering Companu, Inc., and ESCO Corporation. hfarion, Znc. is a major producer of dra clines. Page and ESCO produce buc}:ets for use on dragl:nes. £a c!: cotpanu's r..ethod for determining "rated struck bucket capacity" e.~as identical, con_`orn..ine with accepted .industry standards. hll three tec:~nicians concurred in the opinion that "rated strut}: :,uc.':et capacity" e,•as not a valid constant for deterruninc over l~vrden s•.:e11 factors.