Rock drilling means to drill holes in the rock. In rock drilling engineering, to obtain the ideal drilling effect, the drilling hole should be drilled in the direction of the design requirements. If there is a deviation in drilling, it will affect the effect of drilling, so what are the factors that affect drilling?

1. Rock mass geological conditions

Most influential factor in drilling deviation is actual drilling, especially when drilling in rock formations with complex geological conditions. Generally, degree of drilling deviation is proportional to drilling depth. Experience has shown that drilling angle of a rock drill bit to rock layer is critical. When this angle is less than 15°, drilling direction of a rock drill bit is inclined at an angle parallel to plane of rock junction. Conversely, if a rock is of uniform texture, there will be little or no deviation in drilling.

2. Rock drill bit

Rock drill bit structure and shape also affect drilling deviation. In drilling, regardless of rock drill bit shape, to obtain the best drilling straightness, the worn bit must be reground in time to restore shape of carbide button and maintain carbide’s integrity. In particular, when grinding spherical on the edge, not only spherical, but also steel of skirt body should be ground, and the whole side of skirt body should be ground down, instead of only grinding off steel body near spherical root.

3. Drill rod

If other drilling conditions are same, the larger diameter of drill rod, the higher straightness of drill hole. In addition, the large-diameter drill rod can increase rigidity of rock drilling tools, and ensure that rock drill bit does not swing, which is conducive to smooth discharge of cuttings from hole. Therefore, a guide rod with a diameter larger than drill rod is usually installed at the front of rock drilling tools to drill holes with a diameter larger than 127mm and is directly used to ensure that the hole is drilled with high straightness.

Another way to reduce drilling deviation is to use a center-fluted retract guide bit. Diameter of skirt body is roughly the same as diameter of rock drill bit head, which maximizes guiding performance of rock drill bit in blast hole. Center-fluted retract guide bit is an improved drill bit based on the standard drill bit, which can achieve better drilling straightness. If a guide rod is used, drilling straightness will be ideal.

4. Other factors

Impactor specifications, drill bit and drill pipe design, etc.

In addition to above points, many other factors affect drilling. Although it is impossible to completely avoid drilling deviation, we can reduce the deviation through some methods so as not to affect progress of entire rock drilling project.

Specific method is as follows.

1. Use a drill rod with high hardness, good rigidity and straightness, and make diameter of drill hole close to diameter of drill rod as possible.

2. Use new tubular guide rod to reduce probability of drill rod breaking.

3. Use rock drilling equipment with high drilling accuracy to reduce drilling deviation.

4. Ensure correct propulsion force, increasing rotation speed of rock drilling tools can also reduce drilling deviation.

5. It can also reduce deviation by drilling shallow holes in sections.