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How to judge the grade of rock hardness

Issuing time:2021-04-20 10:22

How to judge the grade of rock hardness


The hardest. i.e., the densest, toughest quartzite, basalt and various otherparticularly hard rocks. (f=20)

Very hard. Very hard granite, quartz porphyry, siliceous schist, relatively hardquartzite, the hardest sandstone and limestone. (f=15)

Hard. Firm Dense granite, very firm sandstone and limestone, quartzveins, firm conglomerate, very firm iron ore. (f=10)

a Hard. Firmness Firmsandstone, limestone, marble, dolomite, pyrite, and unstable granite. (f=8)

Relatively hard. general sandstone and iron ore (f=6)

a Relatively hard. sandyshale and shale sandstone. (f=5)

Moderately hard. firm argillaceous shale, unstable sandstone and limestone, softgravel. (f=4)

Va Mediumlyhard. Various kinds of unstable shale and dense marl. (f=3)

Relatively soft. Weak shale, very soft limestone, chalk, salt rock, gypsum,anthracite, broken sandstone and stony soil. (f=2)

a Relatively soft. gravelsoil, broken shale, bonded gravel, gravel, solid coal, hardened clay. (f=1.5)

Soft. Soft dense clay, soft bituminous coal, hard impact soil, claysoil. (f=1)

a Soft. Soft sandy clay,gravel, loess. (f=0.8)

Soil-like. humus, peat, soft sandy soil, wet sand. (f=0.6)

Loose. sand, mountain gravel accumulation, fine gravel, loose soil, minedcoal. (f=0.5)

Quicksand-like. quicksand, swamp soil, water-bearing loess and other water-bearingsoil. (f=0.3)


A quantitative indicator of the solidity ofthe ore.

People have realized in longterm practicethat some rocks are not easy to break, and some are difficult to break. Rocksthat are difficult to break are generally difficult to drill, and difficult toblast, so their hardness is relatively large, generally speaking, they arerelatively hard. Therefore, people use the concept of rock hardness to expressthe difficulty of rock breaking.

The grade of the hardness is expressed bythe firmness coefficient, also called the hardness coefficient, also called thePlatts hardness coefficient f.

Ruggedness factor f=R/100 (R unit kg/cm2)

In the formula, R—— is the unidirectionalultimate compressive strength value of the standard rock sample.

The commonly used Platts rockclassification method is based on the firmness coefficient to classify therock.

Such as:

Extremely hard rock f=1520 (firm granite,limestone, quartzite, etc.)

Hard rock f=8 10 (such as unstable granite, solid sandstone, etc.)

Medium solid rock f=4 6 (such as ordinarysandstone, iron ore, etc.)

Unsound rock f=0.83 (such as loess, only 0.3)

The solidity of ore rock is also a propertyof resisting external forces, but it and the strength of ore rock are twodifferent concepts.

Strength refers to the performance of orerock against unidirectional action such as compression, tension, bending andshearing. The external force resisted by the robustness is a comprehensiveexternal force. (Such as the combined force of resisting shovel, draft,mechanical breaking, explosives).

Only by judging the rock grade == firmnesscan the appropriate rock drilling tool be selected.


Several common rocks introduction

1. Granite-onedeep acidic igneous rock, belonging to magmatic rock. The crystals of themineral particles are relatively large, and the size of the particles issimilar, showing mosaic and granular crystal structure. Different types ofminerals are arranged in a regular or irregular manner.

2. Andesite-oneneutral eruptive rock. Its composition is equivalent to diorite. It is darkgray, light rose, dark brown and other colors. Mottled structure. Thephenocrysts are mainly plagioclase and dark minerals. Andesite is the mostwidely distributed type of volcanic rock in the orogenic belt.

3. Basalt-onekind of rock with a dense or foamy structure formed by cooling and solidifyingthe magma erupted by a volcano. It belongs to magmatic rock. Basalt isgenerally black, sometimes grayish green and dark purple. Its particles arefine and porphyritic, in which stomatal structure and almond structure arecommon.

4. Sandstone-onerock formed by sand particles transported and deposited on the river bedthrough thousands of years of accumulation and solidification by geophysicalaction. The sandstone has a granular structure and good water permeability. Thesand size is 1/16-2mm, and the particles are particularly fine. For example,the sandstone with a diameter of 1/16-1/250mm is called siltstone. The mainingredients are: quartz content is more than 52%; clay is about 15%; goethiteis about 18%; other substances are more than 10%. If the quartz content is morethan 90%, it is called quartz sandstone.

5. Shaleor mudstone (Mud rock)-one kind of clay rock, formed by compaction, dehydration,and recrystallization of clay materials. It is composed of tiny minerals with aparticle size of less than 1/256mm and has a sheet-like or flake-like layering.It is easy to break into pieces when hit by a hard object, and its waterpermeability is very poor. The difference between shale and mudstone is thatshale has obvious flat bedding, and the particle size of two adjacent layers isobviously different. The thickness of a single layer is less than 25cm and thetotal thickness can reach tens of meters; the bedding of mudstone is notobvious, and the thickness of a single layer is greater than 1 meter, and thetexture is relatively uniform.

6. Limestone-mainlyformed in shallow seas, carbonate rock with calcite as the main component,which belongs to biological sedimentary formation. The structure of limestoneis relatively complex, with two kinds of clastic structure and grain structure.Its lithology is uniform, its hardness is not high, and its main chemicalcomposition is CaCO3. It is easily eroded when encountering karst terrain.

7. Slate-onekind of shallow metamorphic rock, formed from clayey, silty sedimentary rock orintermediate acidic tuff rock and sedimentary tuff after slight metamorphism.Its lithology is dense, with plate-like structure and obvious plate-likecleavage. Slate has a compact particle structure, poor water permeability, highhardness and good wear resistance. It is an ideal product for wall and floordecoration materials.

8. Schist-onecommon regional metamorphic rock. The original rock has been completelyrecrystallized and consists of flaky, columnar and granular minerals.Generally, it is a scale metamorphic structure, a fibrous metamorphic structureand a porphyritic metamorphic structure. It is characterized by a schistositystructure, with relatively fine schistoscopy (schistosity), and theschistosomies are mostly wavy and curved.

9. Marble-onetype of rock represented by marble, including carbonate rocks and relatedmetamorphic rocks. Marble is mostly blocky, with coarser particles, richcolors, and many textures. Compared with granite, it is generally softer, andit is easy to cut into slabs or perform various deep processing.





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