Key considerations for rotary drilling rig bit selection: Double-bottom sand-scooping buckets are widely applicable for soil layers, while embedded double-bottom sand-scooping buckets are suitable for gravel layers. Tubular drill bits are specifically designed for circumferential cutting in hard rock, auger bits break up isolated boulders, and double-layer tubular drill bits efficiently handle pebble layers. High-quality drill teeth, such as bucket teeth, Bauer teeth, cutting teeth, and roller cone teeth, are designed for soil layers, pebbles, rocks, and ultra-hard rocks respectively, directly impacting construction efficiency.#drilling foundation#
How should rotary drilling rigs select the appropriate drill bit for different geological formations?
01 Drill Bit Compatible Formations
► Double-Bottom Sand-Retrieving Drill Bit for Soil Formations
This type of drill bit is particularly suitable for soils such as silt, fine sand, silt, silty clay, and clay, as well as some soil-like soft rocks, such as fully, strongly, and moderately weathered mudstone and argillaceous sandstone. It is the most widely used type of drill bit in the industry.
► Rock-Embedded Double-Bottom Sand-Collecting Bucket
This drill bit is primarily suitable for pebble and gravel layers, as well as moderately weathered soil-like soft rocks, such as moderately weathered argillaceous sandstone and argillaceous conglomerate. For harder rocks with a higher degree of weathering, such as fully or strongly weathered granite, drilling usually requires the use of a spool drill and an auger bit.#drilling foundation#
► Spool Drill
The spool drill is suitable for moderately weathered sandstone with distinct stratification (high core recovery probability), and is also used for girdling hard rock layers. In denser soil layers or some soft rock formations, if the friction drill rod slips, a spool drill can be used to address the issue.
► Rock-Embedded Spiral Drill Bit
This drill bit is particularly suitable for breaking up hard rock formations such as boulders and isolated rocks within the hole. For certain clay formations and medium-density gravelly soils, when the double-bottom sand-scooping drill bit cannot penetrate the soil layer, a spiral drill bit can be tried for drilling.
► Double-layer barrel drill bit
The double-layer barrel drill bit is suitable for drilling through layers of pebbles and boulder with a particle size of 200–500 mm. Its unique design concept is "squeezing," meaning that the crushed pebbles and gravel of varying sizes are compacted inside the barrel and then carried out of the hole. This type of drill bit has been widely used in China, and it is significantly superior to other drill bits in terms of both drilling efficiency and drill bit wear.
► Single-Bottom Sand-Collecting Bucket for Soil Layers
This drill bit functions similarly to the double-bottom sand-collecting bucket, but its side inlet design makes it more efficient when drilling in soil layers. However, due to its lighter weight, it may slip and stop advancing in some hard soil layers, especially when used with a friction rod, thus affecting drilling efficiency.
► Soil Auger Bit
This drill bit is only suitable for small pile diameters and clay layers with high cohesion. Its advantages include a drill bit height of up to 4m, large single-pass depth, and effective avoidance of the difficulty in unloading slag encountered by other drill bits in such projects. Recommended for use within its applicable range.
► Double-Bottom Single-Entrance Drill String
This drill string is generally suitable for boreholes with a diameter ≤1.2m. Its characteristic is a large single-sided inlet, which is very helpful when drilling certain strata, such as gravel strata with a particle size of less than 200mm. However, because the single-entrance design is asymmetrical, the design and manufacturing requirements are relatively high to prevent borehole deviation. For small-diameter piles and suitable geological conditions, this type of drilling tool is recommended for drilling in gravel formations.
02 Drill Teeth Classification and Applications
Drill teeth are the components in a rotary drilling rig system that directly contact the workpiece. Their selection, arrangement angle, and spacing parameters have a decisive impact on construction efficiency. High-quality drill teeth should be crack-free, not easily broken, wear-resistant, and easy to assemble and disassemble. Currently, the most common drill teeth on the market are mainly divided into the following four categories:
► Bucket Teeth
These drill teeth are particularly suitable for drilling in soil layers. Their cutting edges are very sharp, enabling rapid cutting of soil layers. However, please note that they are not suitable for hard strata such as gravel or rock. Suitable for soil drilling, not suitable for gravel or rock layers.
► Bauer Teeth
Compared to bucket teeth, Bauer teeth are designed to be more robust and have higher bending strength, making them less prone to breakage. These drill teeth are often used in large-diameter buckets, especially suitable for drilling small to medium-sized gravel and soft rock. More robust, used in large-diameter buckets, suitable for small to medium-sized gravel and soft rock.
► Cutting Teeth
These are drill teeth specifically designed for rock drilling. Their wear-resistant alloy points provide greater pressure to the rock, making them ideal for rock breaking. Specifically designed for rock drilling, they offer high wear resistance.
► Roller Cone Teeth
These drill teeth are specifically designed for drilling into extremely hard rock, breaking it through crushing. Their unique roller cone rotation design reduces vibration during rock drilling, while the use of wear-resistant alloy cutting tools extends their service life. Suitable for extremely hard rock, crushing it through crushing, and extending service life.#drilling foundation#
