Laserfiche WebLink
• TABLE 1 <br />TYPICAL SUBSIDENCE FACTORS FOR EUROPEAN COAL FIELDS <br />Coalfield and Method of Packing a <br />British coalfields <br />Solid stowing ....................................0.45 <br />Caving or strip-packing .......................... .90 <br />Ruhr coalfield, Germany <br />Pneumatic stowing ................................ .95 <br />Other solid stowing .............................. .50 <br />Caving ............... ........................... .90 <br />North and Pas de Calais coalfield, France <br />Hydraulic stowing ................................0.25-0.35 <br />Pneumatic stowing ................................ .45- .55 <br />Caving ........................................... .ES- .90 <br />Upper Silesia <br />Hydraulic stowing ................................ .12 <br />Caving . ........................................ .70 <br />U.S.S.R.l. <br />Donets and Kizelov districts ..................... .FO <br />Kuznetsk and Karaganda districts ................. .70 <br />Chelybinsk district .......................... .90 <br />1Mining without stowing, which implies caving. <br />• However, he notes observations in U. S. coalfields indicate <br />rather small subsidence factors for caving, and quotes <br />values between 0.5 and O.F based on measurements in <br />Pennsylvania. <br />Gentry and Abel (1978) report values of subsidence <br />factor ranging between 0.51 and 0.71, with the higher values <br />corresponding to subsidence under ridge tops and lower <br />values corresponding to subsidence under draws. Their data <br />were measured at the York Canyon Mine in New Mexico, where <br />the Raton Formation, which overlies the mined seam, is of a <br />somewhat similar character to the Mesaverde Formation at the <br />Orchard Valley Mine. <br />Subsidence Engineers' Handbook (1975, p.10) suggests a <br />subsidence factor of 0.9 for British conditions where multi- <br />seam mining has been practiced, and implies a value of 0.81 <br />in a virgin area. These are higher than values typically <br />reported in U. S. r_oal fields. <br />Based on the available information, we consider that <br />assuming a subsidence factor of 0.7 for the Orchard Valley <br />Mine will result in a realistic, and possibly slightly <br />• - 31 - <br />