Mechanized cut-and-fill mining as applied at the Homestake Mine
Abstract-TheHomestake Mine,located in Lead,SD,has been in business for 113 years.Until 10 years ago,conventional mining methods were ud to extract one. Due to complexities in the ore bodies and integral part of this technology was mechanized cut-and –fill mining .This mining method currently produces about 50% of the annual production and has proven to be safe and economical.AS a result, the Homestake Mine remains competitive in today’s market.
Introduction教育安全平台
The Homestake Mine, located in the Black Hills of South Dakota,has a long history dating back to 1876, In the 113 years of its existence ,a variety of mining methods have been applied to the ore bodies. Some of the more traditional methods included open cut-and-fill, shrinkage, aquare-t,block caving and blasthole sublevel mining.
Due to increasing costs and ore body complexities ,new and innovative mining methods ha
d to be developed. As a result, mechanized cut-and-fill was introduced to mine erratic ore zones and ore areas with dips too shallow effective recovery using vertical crater retreat mining techniques.
Mechanized cut-and-fill mining consists of interconnecting a ries of small ore zones accessible with a common ramp. This affords the flexibility of multiple ore headings to ensure consistent production and high equipment u .
Geology
The Homestake ore body is comprid of metadiments alterd through progressive regional metamorphism.Three main Precambrian rock formations consisting of the oldest Poorman formation, the intermediate Homestake formation, and the youngest Ellison formation, are intricately folded into a ries of synclines and anticlines plunging 10 to 80 southeast and dipping 65 to 70 northeast on the average. Additionally, Tertiary rhyolites and phonolites resulting from intrusive activity cut across all three formations.
The Homestake formatiom,which hosts all ore-grade mineralization,is a sideroplesite-grunerite-quartz schist. Ore bodies are replacement pipes oriented parallel to fold plunges and the gold is erratically associated with quartz , arnopyrite and pyrrhotite. The ore zones, which strike 35 northwest ,can range from 3 to 30 m in width and 9 to 152 m in length .Mineralization may commonly extend for 91 m down 50 to 80 dips . Compressive strengths vary from over 206.8 Mpa to 131 Mpa in lower levels where highly fractured formation is characteristic. Ore grades are determined by extensive diamond core drilling and condary wet-sludge sampling for each stoping block.
Mechanized cut-and-fill stops design
Ore zones are initially delineated by diamond drill holes on 30 m intervals . Once ore is intercepted,drill hole spacing is reduced to 15 m to define the limits of the mineralized zone. A computer program process the information realized from the diamond drilling and produces a cross-ction depiction of the hole date.Geologists then interpret the information to quantity the size and value of the ore body .This information is converted fr
工程尾款om cross ction to plan view and lift maps are constructed on 3-m intervals. The lifts are digitized into parate layers on a computer-aided design system and can be displayed as needed for planning purpo.
Next, the cross ctions and lift maps are reviewed by the planning engineer. Due to safty and productivity advantages , geologic information is initially evaluated for the feasibility of vertical crater retreat mining . If the ore is not amenable to VCR mining , MCF is incorporated.
The mechanized cut-and-fill method requires evaluation of : safety, logistics, ore body configurations , geotechnical considerstions , quality of geologic information and economic viability.
Main mine levels are established on 46-m intervals . From the levels, a footwall ramp ranging from 0% to +18% is designed to effectively access the geologic rerves as mining progress up or down dip . An extraction boreholes is designed along the vertical extent of the ore zone to allow access to various mining horizons. Ventilation consideratio
ns to minimize air recirculation are incorporated and may include boreholes that allow dumping of waste rock into previously mined areas .
Development costs required to bring the ore body into production are calculated and applied to a cost comparision graph to determine the economic viability of the ore zone . The cost comparison graph is constructed using general equations derived from the revenue generated by a specific geologic inventory and the mining this inventory . The equations are as follows :
Money available for development =(Revenue generated)-(Cost)-(Profit) and Feet of development =(Money available)+(Cost per foot)
Where :
初中数学A) Revenue generated considers:
中国三生
1) Variables
a) Tons
b) Grade
c) Price per ounce of gold
2) Constants 秋天思念的诗句
a) 胃火旺最明显症状Recovery
B) Costs :
1) Site specific constants
a) Mining type-location cost per ton of ore
b) Location cost per foot of development
2) 太白湖景区Mine-wide constants
a) ws851Dilution factor
b) Contingency factor to account for unkowns
3) Variable tons
C) Margin of profit where:
