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Typical flow sheets

Typical flow sheets for open-cut mining works

Nowadays, most mining enterprises are equipped with powerful mining machinery and transport facilities. Variety of excavators and vehicles used in a wide range of mining geological conditions requires usage of a big number of various flow sheets for mining works. Enhancement of flow sheets and improvement of performance indicators of mining enterprises are made possible through optimization of parameters and elements of design systems, and quality and quantity proportions of main and auxiliary equipment in various mining conditions.
Typical flow sheets are selected by criteria of achieving best technical and economical results based on prime cost, labor intensity, reduced costs and equipment performance. These sheets determine basic organization of overburden and excavation works, interconnection between individual processes, and options for enhancement of each process individually.
The main requirement is accuracy of sheets, their applicability directly at enterprises. Sheets are designed for particular conditions and specific types of excavators with consideration of efficient organization of works which would provide high performance of mining equipment and transport. Calculated data of flow sheets are accepted on the basis of advanced indicators with observation of rational proportion between the number and performance of loading and transport aids. Rational parameters of elements of design systems are considered.

Main classification features taken into consideration for development of flow sheets are: development system (transportation mode), method of mined rock excavation, method of mined rock preparation for excavation, type of loading equipment and transport means. Additional features are: loading method, number of round of excavator during slope excavation, procedure of spotting for loading, etc.

According to transport types, there are sheets with railway, automobile, and conveyer transport. Transport type is established according to haulage, seam conditions, volumes of mined rock moving, quarry field size. Railway transport is mainly used for considerable haulages (over 3 km), large volumes of mined rock on strip pits of shallow and average depth. Automobile transport is preferable for small strip pit areas with short haulages (less than 3 km.) and relatively small volumes of mined rock. Conveyer transport is usually used for transporting coal from deep levels.

According to mined rock excavation methods, there are sheets of bulk and selective mining. Bulk mining means that a bench is worked without dividing mined rock into separate components (coal and rock). Selective mining means coal and rock are excavated separately. Depending on conditions of rock and types of Loading equipment, selective mining is conducted via organization of separate rounds, selective scooping, temporary storage of coal or rock, and application of additional equipment. Right choice of selective mining sheets ensures possibility of considerable reduction of operational coal loss.

According to methods of mined rock preparation for excavation, there are three groups of sheets: without ripping; with drill-and-fire ripping; with mechanical ripping. No-ripping sheets are used for soft rocks of categories I—II excavation difficulty. Drill-and-fire works are conducted in rocks of medium and high hardness. Mechanical ripping is used in rocks of medium hardness during layer-by-layer excavation of seams of complex structure.

According to types of loading equipment, there are sheets with power shovels, drag lines, loaders, and, in special cases, combinations of power shovels and ripper-dozers. Power shovels are widely used for loading coal and rock into vehicles, drag lines are used for rock piling. In some cases, drag lines are used for loading mined rock into vehicles. In the last few years, hydraulic excavators have been used widely across the country’s mining areas for having high performance in selective mining even in conditions of complex and deep faces
Besides, sheets can be classified according to:
  • Loading methods: with upper-deck or lower-deck loading,
  • Direction of slope excavation — with traverse and longitudinal cuts,
  • Number of excavator’s rounds — with one or several rounds,
  • Method of spotting for loadingу — dead end, ring, through.
© 2012. Geotechnology
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