I. Mechanical strength of rock and minerals Strength is one of the important properties of solids. It is expressed in the resistance to external forces and is determined by the combination of internal solid particles. When crushing ore, it is subject to the resistance caused by the mechanical strength of the ore. The difficulty of rock crushing is related to this resistance. There are two requirements for the crushing work: the machinery used should be strong enough and reliable; for fine ore, the requirements are easy and smooth. To solve these two problems, it is necessary to study the mechanical strength of the rock. The compressive strength, tensile strength, shear strength and flexural strength measured under static load are commonly used to indicate the resistance to fracture resistance of rock ore. The compressive strength is the highest, the shear strength is second, the bending strength is small, and the tensile strength is the smallest. If the compressive strength is 1, the other strength is only a small fraction of it. Sometimes using the Platts coefficient (f, MM Protogiyaknov) as a coefficient of rock robustness classification, if the compressive strength is used to determine the Platts coefficient, it is approximately equal to one percent of the compressive strength. . According to the Platts coefficient, the rock can be divided into ten grades according to the firmness, and the f value is from 0.3 to 20. The rock with a large f value is also high in firmness. The compressive test made by the test pieces of different sizes of the same rock ore indicates that the test piece has a small size and its compressive strength is large. In grinding, the finer the ore, the harder it is to grind. This is because the macroscopic and microscopic cracks present in the small test piece are less than those in the large test piece, and thus its strength is relatively high. Quartz is usually used to represent a medium hardness ore with a coefficient of friability and a grindability of 1. The strength of the hard ore is large, the coefficient of friability and the grindability coefficient are both less than 1, and the productivity of the crushing machine is lower than that of the treated hard ore. The strength of the soft ore is small, both of which are greater than 1, and the productivity of the crushing machine is greater than that of the treated hard ore.
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Second, the smashability and grindability Fragability and grindability reflect the difficulty of the ore being broken, it depends on the mechanical strength of the ore. Mechanical crushing of the same, under the same conditions, as compared with the processing of hard mineral ore processing soft, low productivity of the former case, the power consumption is also large. The severability coefficient and grindability coefficient of the ore proposed in combination with the crushing and grinding process not only reflect the firmness of the ore, but also can be used to quantitatively measure the process index of the crushing machine. Therefore, it is often used in subsequent calculations. To.
There are many ways to represent the coefficient of friability and the coefficient of grindability. The following are commonly used in mineral processing : 
According to the requirements of crushing or grinding, the rock ore strength classification table is neither unified nor perfect. The domestic rock ore strength data is collected less. Therefore, it is difficult to compile the crushing and grinding according to the actual situation in China. The classification of rock ore strength required by the mine. At present, there are many Platts rock classifications. In order to fully understand this classification method, the details of this classification are introduced here, and the Platts coefficient of the ore processed by some factories in China (the following table) is attached. The classification of rock ore strength used in crushing and grinding may be simplified by the Platts rock classification. Simplified results, the books are not consistent, there are simplified to three, four or five. According to the strength grade of rock ore, the coefficient of friability and the grindability coefficient are divided and used for the calculation of the production capacity of the equipment. When describing these calculation methods, the grades of rock used in each method are also listed. Only the general situation is introduced here for reference. [next]
Mechanical strength, smashability and grindability of rock ore
Platts Rock Rating Table
grade
Ruggedness
rock
f
The f-value of ore processed by some factories in China
1
2
3
4
5
I
The strongest rock
The most sturdy, meticulous and resilient quartzite and basalt , a variety of other particularly strong rocks
20
Dagushan hematite (12 to 18), Dagushan magnetite (12 to 16), Donganshan iron (12 to 18), Tieshan (12 ~ 16) side slope (12 to 16) Hainan Iron Mine (12~15) Daye Iron Mine (10~16), Dajishan Tungsten Mine (10~14)
Tonghua copper ore (8 to 12), Tongguanshan (9 to 17) SHOUWANGFEN (8 to 12), lead zinc ore Huanren (8 to 12), a new copper smelting (8 to 10), Red Hill MA (8~9), Shuangtashan Iron Mine (9~13), Yinmin Copper Mine (8~10), Fushan Iron Mine (8~12) Shuikoushan Lead-Zinc Mine (8~10), Qingchengzi Lead Mine ( 8)
Huatong (6~10), ratio (6~10)
II
Very strong rock
Very sturdy granitic rock, quartz porphyry, very strong
Granite , tantalum schist, less solid quartzite than the upper one, the strongest sandstone and limestone
15
III
III a
Sturdy rock
Sturdy rock
Granite (dense) and granitic rocks, very strong
Sandstone and limestone, quartz veins, strong conglomerate, extremely strong iron ore
Limestone (sturdy), unsturdy granite, sturdy sandstone, sturdy marble and dolomite , pyrite
10
8
IV
IV a
Rough rock
Rough rock
General sandstone, iron ore
Tantalum shale , shale sandstone
6
5
V
V a
Medium rock
Medium rock
Sturdy clayy rock, not strong sandstone and lime
Rock various shale (not strong), dense marl
4
3
VI
VI a
Very weak rock
Very weak rock
Weak shale, very weak limestone, chalk , rock salt,
Gypsum, frozen soil, anthracite, ordinary marl, crushed sandstone, cemented gravel, stony soil
Crushed soil, broken shale, condensed gravel
And gravel, sturdy coal, hardened clay
2
1.5
VII
VII a
Weak rock
Weak rock
Clay (dense), weak bituminous coal, strong alluvium - clay soil
Light sandy clay, loess, gravel
1.0
0.8
VIII
Earthy rock
Humus, peat, light sandy soil, wet sand
0.6
IX
Loose rock
Sand, hawthorn accumulation, fine gravel, loose soil, coal collected
0.5
X
Sandy rock
Sand drift, swamp soil, watery loess and other water-bearing soil
0.3
1 When classifying each type of rock to this or that level, it is not only by its name, but also by the physical state of the rock and by its robustness compared to the rocks listed in the rating table. Weathered, broken, broken into individual, through the fault-squeezed, close to the surface of the state of the rock, in general, it should be divided into a lower level than the same state of the same rock.
2 The above-mentioned rock solidity coefficient can be considered as a characterization of the relative robustness of different aspects of rock. Its significance in mining is: 1) extractability during manual mining; 2) shallow-eye and deep-hole chiseling; 3) Blasting when applying explosives; 4) Stability during falling; 5) Pressure acting on the support, etc.
At the same time, however, it must be noted that the values ​​indicated in the rating table are for rocks of a certain type of rock (eg shale, quartzite, limestone, etc.) rather than one of the other rocks. In fact, when determining the value of f in a particular case, it must be very careful, and this f-value is different in different situations.