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In process of conquering nature, it is inevitable to struggle against rocks for human beings. Nowadays, mining of various mineral resources, and construction of energy and transportation such as railways, highways, water conservancy, and hydropower all require rock drilling. Rock drilling means to drill holes in the rock, which directly affects the speed, quality, safety, and cost of the subsequent process and engineering construction.
There are all kinds of rocks in nature, composition, structure, and other characteristics of different rocks are different.
Type of rock
Rocks can be divided into three categories according to their origin igneous rocks, sedimentary rocks, and metamorphic rocks.
1. Igneous rock
Igneous rock is formed by magma cooling consolidation, it is also called magmatic rock and is a hard and complete rock. Typical igneous rocks are granite and granodiorite.
These rocks are easier to drill by impact if they have not been severely fractured and weathered. They are generally too hard for rotary drilling except with heavy rigs with vertical pressure and torque, but drill bit wear is a serious problem.
2. Sedimentary rocks
Most sedimentary rocks have undergone cementation, compaction, and recrystallization. Representative sedimentary rocks are limestone and sandstone.
Hardness of limestone varies greatly. Hard limestone can be drilled with a pneumatic or heavy-duty rotary drill, while soft limestone is best drilled with a rotary drill.
Sandstone is an abrasive rock, rotary drilling rigs generally cannot be used, but it is easier to drill with a pneumatic rock drill.
3. Metamorphic rocks
Metamorphic rock is formed by igneous rock and sedimentary rock through metamorphism. A typical metamorphic rock is quartzite, which is formed by metamorphism of siliceous rock (pure SiO2). Generally, pneumatic rock drill is used to drill.
The characteristics of rock, such as hardness and abrasion, determine the drillability, blast ability, and drilling method of rock. So rock drilling methods of different rocks.
Recommended drilling methods for different rocks
Igneous rock
| Igneous rock | Hardness and corrosion | |||
|---|---|---|---|---|
| abrasion | moderately abrasive | less abrasion | weathering | |
| Rock | fine crystalline rock, compact feldspar, granite porphyry, granodiorite, granite, pegmatite, quartz porphyry | olivine basalt, quartz andesite, olivine gabbro, quartz diorite | andesite, basalt, diorite, gabbro, syenite | serpentinite, “red” basalt, kaolinized granite |
| Drilling way | small hand-held rock drill (small diameter hole)
heavy-duty guide drill φ50-102mm DTH drill φ102-150mm heavy swiveling drill φ>150mm |
heavy or medium hand-held rock drill, guide drill, DTH drill, heavy swiveling drill, hole ≥150mm | swiveling drill | |
Metamorphic rocks
| Metamorphic rocks | Hardness and corrosion | ||
|---|---|---|---|
| hard + abrasion | medium | softer | |
| Rock | leucite, quartz schist, quartzite, gneiss | amphibole schist, mica schist, dolomitic marble | slate, phyllite, chlorite schist, marble |
| Drilling way | heavy pneumatic rock drill | medium to heavy pneumatic rock drill | medium to heavy-duty swiveling drill |
Sedimentary rock
| Sedimentary rock | Hardness and corrosion | ||||
|---|---|---|---|---|---|
| hard + abrasion | corrosive, slightly less hard | corrosive, brittle | Non-corrosive， hard | Non-corrosive, soft | |
| Rock | flint, hornstone, sedimentary quartzite, hard sandstone, quartz conglomerate | silt rock, volcanic ash, silica limestone, coarse sandstone, agglomerate | brittle sandstone, calcareous sandstone, and some coarse sandstone | limestone, mudstone, brittle sandstone | marl, mudstone, shale, chalk, coal |
| Drilling way | heavy pneumatic rock drill | medium heavy pneumatic rock drill or heavy swiveling drill | light swiveling drill | medium to heavy pneumatic rock drill, DTH drill, or heavy swiveling drill | twist drill, swiveling drill |
Because of differences in composition and physical and mechanical properties of rocks, it is difficult to find two identical rocks on Earth. However, we can find the most suitable rock drilling method according to hardness and abrasive properties of rock, such as type of rock drill (light and heavy), and rock crushing method (including cutting, shearing, crushing, and squashing). Only by choosing the most suitable rock drilling method can project progress be guaranteed effectively and drilling efficiency is improved.
