Rock drillability grading and rock hardness level table

Details:SANYOU   |  2021-01-18
   

under certain technical conditions, rooks are graded according to its drillability. Depending on the drilling method, core drilling can divide into 12 grades, details please consult “Rock 12 grade scale “issued in 1958 by Ministry of Geology of China



     

·         Rock drillability classification


     

Usually we take as soft rock, as medium hard rock, as hard rock; Ⅹ、Ⅺ、Ⅻ as rigid rock for convenient use.

·           Drillability of rock is classification of rock resistance to stress and breakage during drilling, that is the whether the rock is easy to break. According to drillability can divided as below:



        loose ground
     

Representative: redeposited loess, lateritite, loose sandy soil, diatomite and peaty humus layer. (drillability:7.50 m/h)


        Softer loose rock
Representative: loess layer, red soil, floppy turf bed, clay and sandy soils with 10%-20% gravel, floppy bolus alba and the humus layer containing plant roots. ( drillability:4.00 m/h)

      ⅢSoft rock

 Representative: Strong weathered rock, slate, phyllite and schist, slight agglutinating sand layer, sandy soil with 20% gravel, loess layer, gypsum soil layer, marlstone, talc-shcist, lignite, bitumite. ( drillability:2.45 m/h


      ⅣLittle soft rock

·         Representative: shale, sandy shale, oil shale, macker, calcareous shale, marlstone, argillaceous sandstone, limestone, dolomite, strongly weathered peridotite, serpentite and limestone, medium hard, coal bed, halite, clay layer, volcanic marl stone and frozen sandstone.


      Little hard rock

·           Representative: pebble, detritus, gravel layer, argillite, green mud slate, phyllite, schist, fine crystalline limestone, marble, soft sandstone, serpentinite, dunite, olivine rock, trachyte, splint coal, anthracite, frozen coarse grained sand, gravel and frozen earth. (Drillability:1.15 m/h)


       Ⅵ-Medium hard rock

   Representative: chlorite, mica, sericite slate, phyllite, schist, epidote, lightly silicified limestone, calcite, Calcareous conglomerate, arkose, quartz sandstone, hornblendite, diopsidite and frozen gravel.

·           一一:硬岩 Hard rock

Representative: Silicified sericite slate, phyllite, schist, gneiss, epidosite, carbonated rock, quartzite containing magnetite and hematite, conglomerate rock, basalt, diabase, andesite, quartz porphyry.

     Ⅹ--:坚硬岩 Rigid rock

Representative: fine granite, granodiorite, granitic gneiss, rhyolite, corundolite, blout, the hardest iron horn shale, silexite.


      ⅫMost rigid rock
 Representative: Unweathered dense quartzite, jasper, pure natixene corundum, quartz, silex and jade. (Drillability: 0.045m/h)
     

Factors affecting rock drillability

Rock drillability is not an inherent property, it depends on rock characteristic, drilling technology and technical conditions

(1)  、Rock characteristic; include mineral composition, structural characteristics, physical properties and mechanical properties

(2)、The direct influencing factor is the mechanical property.

Rock hardness levels

Rock level

Solidness

Representative

Most solid

The most solid, compact and ductile quartzite,

 basalt and other various solid rock. f20

The most solid

The most solid granite, quartz porphyry, siliceous schist, relative rigid quartzite,

Most rigid sandstone and limestone. (f=15)

 Solid

Dense granitevery solid sandstone and limestonequartz vein

solid conglomerate rock, very solid iron ore.  (f=10)

a

Solid

Solid sandstonelimestonemarbledolomitepyriteunsolid granite.f=8)

More solid

Ordinary sandstoneiron oref=6)

a

More solid

sandy shaleshaly sandstonef=5) 

 Medium solid 

Solid muddy shale unstable sandstone, limestonesoft gravel.f=4)

a

Medium solid  

Various unsolid shalecompact marlstone (f=3)

Soft 

软弱页岩,很软的石灰岩,白至,盐岩,石膏,无烟煤,破碎的砂岩和石质土壤。 (f=2)

a

Soft 

Gravel soilcrush shale, bond grave, detritussolid coalsclerotic clayf=1.5)

Soft 

软致密粘土,较软的烟煤,坚固的冲击土层,粘土质土壤。(f=1)

a

soft 

soft sandy claygravelloessf=0.8)

Earthy 

humuspeatsoft sandy soilgreen sandf=0.6)

Granular loose

Sand, gravel pile, fine gravel, loose soil, mined coal (f=0.5)

·          Quicksand shape

·         quicksandmarshy soilswater-bearing loess

·         and other water-bearing soil  (f=03 ) A






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