How to choose drill bits based on different formations?

The rotary drilling rig is the most common piece of equipment in the current pile construction. Since the geology of each place is different, how to choose the appropriate drill bit has become a key issue in the piling process. Today we will talk about how to choose the rotary drilling rig bit after understanding the geological characteristics of the construction site.


1. Soil double-bottom sand fishing bucket


It is suitable for silt, fine sand, silt, silty clay, clay, and some types of soil soft rock, such as fully, strongly weathered and moderately weathered mudstone, argillaceous sandstone, etc.; it is the most widely used drill bit in the industry.


2. Rock-socketed double-bottom sand bucket


It is suitable for egg and gravel layers, moderately weathered soil-like soft rocks, such as moderately weathered argillaceous sandstone, argillaceous conglomerate, etc. Harder rocks with a higher degree of weathering, such as full and strongly weathered granite, etc., often need to be used with barrel drills and auger bits when drilling into hard rocks.


3. Barrel drill


It is suitable for moderately weathered sandstone with obvious stratification (high probability of coring), and circumcision of hard rock formations. In the soil layer with high density, or some soft rock formations, when the friction drill pipe is selected to cause slippage, you can try to use the barrel drill to deal with it.


4. Rock-socketed auger bit


It is suitable for crushing boulders in holes, boulders and hard rock formations. For some clay formations and medium-density pebble soil, when the double-bottom sand bucket in the soil layer cannot be drilled, you can try to use the auger bit for drilling.


5. Double barrel drill


It is suitable for drilling in eggs and boulder layers with a particle size of 200-500mm. The double-layer barrel drill adopts a brand-new drilling idea “squeeze”. The broken pebbles of different sizes are squeezed into the cylinder and then taken out of the hole. When designing, the diameter of the outer cylinder is designed according to the diameter of the pile, and the diameter of the inner cylinder is designed according to the average particle size of the pebbles. The inner cylinder is higher than the outer cylinder. This drilling tool has been widely used in China, and its drilling efficiency and tooth loss are obviously superior to other drilling tools.


6. Single bottom sand bucket for soil layer


The function of this drill bit is similar to that of the double-bottom sand dredging bucket. The advantage is that it has a side soil inlet, and it does not need to back-drill and close the bucket door, so the drilling efficiency for the soil layer is higher. The disadvantage is that it is light in weight. For some hard soil layers, especially when used with friction rods, it may slip and fail to advance, which seriously affects the drilling efficiency.


7. Soil auger bit


It is only suitable for clay layers with small pile diameters and high cohesion. The advantage is that the drill bit height can reach up to 4m, the single footage is large, and it can effectively avoid the difficulty of unloading slag in such projects with other drill bits. It is recommended to use within the applicable range.


8. Double Bottom Single Door Drilling Tools


Generally, it is a drilling tool with a diameter of ≤1.2m. Compared with the double-bottom double-door drilling tool, it has a larger single-side soil inlet, which is more conducive to the drilling of some formations, such as the pebble formation with a particle size below 200mm. However, due to the asymmetric structure of the single-leaf door, there are high requirements for design or production, otherwise, the phenomenon of partial hole will easily occur. This bit is recommended for drilling in pebble formations with small pile diameters ≤1.2m.


Classification and use of drill teeth


The drill tooth is part of the rotary drilling rig system that directly contacts the work object. Whether its selection, arrangement angle, arrangement spacing and other parameters are correct or not has a decisive effect on the construction efficiency. A good drill tooth should have the characteristics of no cracks, continuous breaking, wear resistance, and easy disassembly and assembly.


At present, there are four types of common drill button


1) Bucket teeth


Suitable for drilling in soil layers, with sharp teeth and fast cutting speed, and cannot be used in hard formations such as pebbles and rock formations.


2) Bauer’s teeth


Compared with bucket teeth, they are thicker and not easy to break. They are used for large-diameter soil buckets and are suitable for small and medium-sized pebbles and soft rocks.


3) Picks


rock drill teeth, wear-resistant alloy points provide greater pressure on the rock, suitable for rock crushing.


4) Cone teeth


Suitable for superhard rock drilling, crushing and crushing rocks, the rotation of the cones reduces rock-entry vibration, and the wear-resistant alloy knives prolong the service life.

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