July 29, 2021
A quantitative indicator of the solidity of the ore.
People have realized in longterm practice that some rocks are not easy to break, and some are difficult to break. Rocks that are difficult to break are generally difficult to drill, and difficult to blast, so they're hardness is relatively large, generally speaking, they are relatively hard. Therefore, people use the concept of rock hardness to express the difficulty of rock-breaking.
The grade of the hardness is expressed by the firmness coefficient, also called the hardness coefficient, also called the Platts hardness coefficient f.
Ruggedness factor f=R/100 (R unit kg/cm2)
In the formula, R-- is the unidirectional ultimate compressive strength value of the standard rock sample.
The commonly used Platts rock classification method is based on the firmness coefficient to classify the rock.
1. Extremely hard rock f=15~ 20 (from granite, limestone, quartzite, etc.)
2. Hard rock f=8 ~10 (such as unstable granite, solid sandstone, etc.)
3. Medium solid rock f=4 ~6 (such as ordinary sandstone, iron ore, etc.)
4. Unsound rock f=0.8~3 (such as loess, only 0.3)
The solidity of ore rock is also a property of resisting external forces, but it and the strength of ore rock are two different concepts.
Strength refers to the performance of ore rock against unidirectional action such as compression, tension, bending and shearing. The external force resisted by the robustness is a comprehensive external force. (Such as the combined force of resisting shovel, draft, mechanical breaking, explosives).
Only by judging the rock grade = firmness can the appropriate rock drilling tool be selected.