The self-drilling hollow anchor system consists of a hollow anchor bar, coupler, nut, plate, drill bit, and centralizer. The system combines drilling, grouting, and anchoring at one time, and is especially suitable for the construction of weathered rock, gravel layer, backfill soil, sand and gravel layer, etc., which are difficult to form holes.

 

What is Drill Bits?

The drill bit is a key component for drilling holes and realizing the self-drilling function. It is characterized by one-time, and different types of drill bits are suitable for different geological conditions. When the self-drilling hollow anchor bar is installed to the design depth, the drill bit will be left in the borehole. Its processing technology can be divided into machining or casting.

 

Common Types of Drill Bits

1. Hardened Cross-cut Drill Bit

Applicable geological conditions: Sand, fills gravel, soft rock, etc.

2. TC cross-cut drill bit

Applicable geological conditions: Softer sedimentary rocks, marls, mudstones, siltstone

3. Tungsten Carbide Button Drill Bit

Applicable geological conditions: Weathered rock, rubble, limestone

4. Clay bit

Applicable geological conditions: Clay, soft soil, marl, loose sand /gravel

 

Common quality problems and control methods of drill bits

1. Alloy damage

Cause analysis: welding cracks or improper operation

Consequences: The construction efficiency and service life of the drill bit are reduced, and it is even impossible to drill.

Solution: rework to welding

2. Fracture of the alloy button

Reason analysis: Usually caused by the poor quality of the button drill bit

Consequences: The drilling effect, drilling depth, and efficiency will be decreased

Solution: Choose an alloy material that is more suitable for hard rock formations

3. Oil leakage was found in the drill bit spraying process

Cause analysis: casting defects such as shrinkage cavity and shrinkage porosity

Consequence: Short service life of the drill bit

Solution: The drill bit manufacturer should improve the casting process, and conducts an inspection after improving the process.

4. Breaks of the drill bit while drilling

Reason analysis: The structure design of the drill bit is unreasonable, and the wall thickness is too thin and does not meet the actual requirements.

Consequences: Reduced drilling life and high scrap rate

Solution: Change the original design to increase the wall thickness, and improve the strength.

The self-drilling hollow anchor system consists of a hollow anchor bar, coupler, nut, plate, drill bit, and centralizer. The system combines drilling, grouting, and anchoring at one time, and is especially suitable for the construction of weathered rock, gravel layer, backfill soil, sand and gravel layer, etc., which are difficult to form holes.

 

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Categories

Tunneling in Rock

Keywords

rock bolt in tunnel, self drilling rock bolts, rock drill bit