1. Classification of common rotary drill bits
Common rotary drill bits include auger drills, rotary buckets, cartridge core drills, bottom drills, impact drills, punch cone drills and hydraulic grabs.
1, 1 auger bit
(1) Cone: Double-headed double-snail, suitable for hard bedrock. Double-headed single screw, suitable for weathering bedrock, pebbles, frozen soil, etc. The above drill bit is equipped with various picks, and many types of drill bits can be derived through the changes of the tooth type, the pitch and the spiral angle.
(2) Straight auger bit:
a, tooth straight snail
Double-headed double screw, suitable for sand, small-diameter gravel layer with poor cementation; double-headed single screw, suitable for sand and soil layer; single-headed single screw, suitable for large-diameter pebble with poor cementation, cohesive soil and hard clay .
b. Pick-tooth straight snail: There are double snail, triple snail and four snail, suitable for hard bedrock or gravel.
1, 2 rotary drilling bucket
According to the installed teeth, it can be divided into a picking bucket and a bucket drill; according to the number of bottom plates, it can be divided into double bottom bucket and single layer bottom bucket; according to the number of opening doors, it can be divided into double open door bucket and single open door bucket; The taper can be divided into a cone bucket drill and a straight bucket drill; according to the shape of the low plate, it can be divided into a bottom drill and a flat drill. The above structural forms are combined with each other, and with the change of the vent hole and the door opening mechanism, dozens of rotary drilling hoppers can be combined. Generally speaking, the double bottom drilling hopper is suitable for a wide range of strata. The single bottom is only suitable for the viscous soil layer. The double hoist is suitable for a wide range of ground. The single hoist is only used for large diameter pebbles and Hard clay.
1, 3 barrel core drill bit
There are two common types: the pick tube drill (for medium hard bedrock and gravel) and the roller drill (for hard bedrock and large boulders). Among the two types of drills of the barrel core drill, the core take-up device and the core-free device are mainly determined by the difficulty of coring. Because the cone-core coring bit is mainly used for hard rock drilling, and the annular area of ​​the drill is large, if there are conditions, it can also be installed with reverse circulation drilling in the drill part to improve the drilling efficiency.
1,4 expansion drill
On the basis that the pile diameter does not increase the pile depth, in order to improve the bearing capacity of the single pile, the design department often realizes by expanding the bottom pile. The construction of the rotary drilling rig can be constructed without any modification, and only the expansion is required. The bottom bit can be used. Expanded bottom drills are commonly used in mechanical type. These drills are simple to use and maintain. They are open and open. The open mechanism is generally four-bar linkage for soil layer, strong wind and mid-weather. The formation is even hard rock. Since the rotary drilling is a non-circular drilling, after the bottoming is completed, the slag can be used to clear the slag.
1,5 impact drill bit, punch cone drill bit
It is particularly effective to drill large diameter pebbles, large boulders and hard bedrocks, using impact drills, rushing cone drills and rotary drilling. The use of these drills is carried out by the hook of the rotary excavator, because there must be Impact, so the secondary hook is required to have a free rope release function to be better.
1,6 hydraulic grab
At present, the construction work of continuous wall and cut-off wall is becoming more and more. If the rotary drilling rig is slightly modified, it can be operated. The opening and closing of the hydraulic grab is driven by hydraulic pressure. There is only one cylinder on the hydraulic grab, so only Need to enter and exit two oil pipes, one control valve can be.
2. Select the drill bit according to the geological conditions
The main function of the rotary drilling rig is to form a hole in the surface of the earth. The working object is rock. Due to the shallow depth of the pile hole, the rock undergoes structural movement, natural mechanical and chemical effects, structure, particle size, porosity and cementation. Complex changes have occurred in the production, compressive strength, etc., and the vastness of China's original size, so the object of rotary drilling rig work is particularly complicated. In summary, there are the following categories.
According to lithology (common), it is composed of shale, sandstone, limestone, granite, etc.; it is divided into magmatic rocks, sedimentary rocks and metamorphic rocks according to genesis; it is divided into solid, plastic and loose according to mechanical characteristics. So how do you choose the drill bit according to the situation of the formation? The following classification is introduced.
(1) Clay: Rotary digging bucket with single bottom is used. If the diameter is too small, two buckets or a bucket with earthmoving plate can be used.
(2) The sludge, the viscous soil layer, the sand, the poorly cemented pebble layer, and the double-drilled drilling rig.
(3) Hard clay: use single-input soil (both single and double bottoms) to dig the drill bucket, or the straight screw.
(4) Permafrost layer: Available straight-toothed screw drills and rotary-drilling buckets with low ice content, and available cone-shaped spiral drills with large ice volume. It should be noted that the auger bit is used for soil layer (except for It is effective outside the silt, but it must be used without groundwater to avoid seizure and cause seizure. (5) Cemented gravel and strongly weathered rock: Rotary drilling rig with conical auger bit and double bottom is required (single port with larger particle size and double port with smaller particle size)
(6) Stroke base rock: equipped with a pick-up type core drill bit--conical spiral drill bit--double bottom bottom rotary drilling drill, or pick straight straight spiral drill bit--double bottom bottom rotary drilling drill.
(7) Micro-weathered bedrock: equipped with a cone-shaped coring bit--conical spiral drill bit--the double-drilled rotary drilling drill requires a step-by-step drilling process if the diameter is too large.
3. Select the drill bit according to the function of the rotary drilling rig
If the rotary drilling rig has a continuous function, it can be equipped with a liquid grab or two-wheel milling for continuous construction. If the sub-winding has an automatic rope release function, the impact drill and the rushing drill can be used to drill large diameter pebbles or boulders. If equipped with a gas chamber and a faucet, gas-liquid drilling is possible. If it is equipped with a double power head or a pipe machine, it can be drilled into the casing, which is an effective method to solve the problem of flowing sand, crushing gravel and silt.
4. Select the drill bit according to other factors
If the thickness of the sinking is relatively strict or when drilling is being carried out, a special cleaning bucket is required. When the inlet sleeve is drilled, the gap between the drill bit and the sleeve is small. In order to prevent the drill bit from hitting the sleeve and reduce the suction effect, the drill bit should be provided with a vent hole, and the drill bit is provided with a guiding device, the opening and closing device As close as possible to the center of the drill bit, it is best to have the machine integrated. This special problem can also be solved by selecting a combination of drill bits.
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