How to choose rotary drilling bits for different soil and rock layers？

Suitable for moderately weathered sandstone with distinct stratification (high probability of core retrieval), as well as the annular cutting of hard rock layers. In highly dense soil layers or some soft rock formations, when slippage occurs due to the selection of friction-type Kelly bars, a core barrel can be tried to resolve the issue.

Suitable for breaking boulders, solitary rocks, and hard rock layers inside the hole. For certain clay formations and moderately dense gravelly soil where drilling is impossible using the soil double-bottom bucket, an auger drill bit can be tried for drilling.

Suitable for drilling in gravel and boulder layers with a particle size of 200–500 mm. The double-wall core barrel adopts a brand-new drilling concept of "squeezing". That is, cobbles and gravels of different sizes are compacted inside the barrel and then brought out of the hole. During design, the outer barrel diameter is designed according to the pile hole diameter, and the inner barrel diameter is designed according to the average particle size of the cobbles, with the inner barrel being higher than the outer barrel. This drilling tool has been widely used in China, and its drilling efficiency and tooth wear rate are significantly superior to other drilling tools.

This drill bit has similar functions to the double-bottom drilling bucket. Its advantage lies in its side soil inlet, and it does not require reverse rotation to close the bucket gate, which offers higher drilling efficiency for soil layers. The disadvantage is its lighter weight; when dealing with some hard soil layers—especially when used with friction bars—slippage without penetration may occur, severely affecting drilling efficiency.

Only suitable for small pile diameters and clay layers with high cohesion. The advantage is that the drill bit height can reach up to 4 meters, allowing for a large penetration amount per single run, and it can effectively avoid the problem of difficult muck discharging encountered by other drill bits in this type of project. It is recommended for use within its applicable scope.

Generally refers to drilling tools with a diameter ≤ 1.2 m. Compared to the double-bottom double-opening drilling tool, it features a larger single-sided soil inlet, which is more helpful for drilling in certain formations, such as cobble layers with a particle size below 200 mm. However, because the single-opening gate has an asymmetrical structure, it places high demands on design or production; otherwise, hole deviation can easily occur. For cobble layer drilling with small pile diameters ≤ 1.2 m, this drill bit is recommended.Classification and Applications of Drilling Teeth:

Drilling teeth are the components of the rotary drilling rig system that come into direct contact with the target work material. Whether parameters such as their selection, layout angle, and layout spacing are correct plays a decisive role in construction efficiency. High-quality drilling teeth should possess characteristics such as being crack-free, unbreakable, wear-resistant, and easy to disassemble.

Currently, there are four common types of drilling teeth (pictured above):