Boreholes are generally described by four characteristics: straight, depth, straightness and stability.

1. Hole diameter

The diameter of the drilled hole depends on the purpose for which the hole is used. In blasting hole drilling operations, there are many factors that affect the selection of holes. For example, the size of rock particles required after rock breaking; the type of blasting selected; the "quality" requirements of the rock particles blasted (the smoothness of the particle surface and the proportion of breakage); the allowable surface vibration during blasting operations. In larger quarries or large open pit mines, the use of large aperture blasting operations often reduces the cost of drilling and blasting per ton of rock. In the underground drilling operation, the mining equipment is limited by the underground space. In the drilling operation of the water well hole, the size of the rock hole depends on the diameter of the pipe or the diameter requirements of the supporting equipment required by the water pump. In terms of rock support holes, the diameter of different bolts is the determining factor.

2. Depth of the hole

The depth of the hole is affected by the drilling equipment, and only short drilling tools can be selected in a limited space. Short drilling tools in the form of threaded connections are necessary for rock drilling in limited spaces. In the drilling of blasted rock holes (horizontal or vertical holes), the depth of the hole is slightly deeper than the theoretical depth or terrace height. Under some rock drilling conditions, the depth of drilling is required to be deeper (50-70 meters or more). Generally, the down-the-hole drilling method is used instead of the top hammer impact drilling method. The energy transfer of the down-the-hole drilling method and the powder discharge effect under the deep hole condition are more efficient.

3. Straightness of hole

The straightness of the hole is a factor that varies greatly with the type of rock and natural conditions, the selected mining method and the selected mining equipment. In horizontal and inclined rock drilling, the weight of the drilling tool will also affect the offset of the hole. When drilling deep blasting holes, the drilled rock holes must be kept as straight as possible so that the charge can accurately obtain the desired blasting effect.

In some types of rock drilling operations, deep rock holes are often drilled, and the straightness of the rock holes is extremely high, such as pipe holes or cable holes. Even the requirements for water well holes are very strict in order to enable a smooth installation of water pipes and pumps.

The use of different types of guiding equipment, such as: guiding bit, guiding drill pipe and guiding drill pipe, will improve the straightness of the hole. In addition to the offset of the rock hole itself, the direction of the drilling is also related to the degree of adjustment of the propulsion beam and the accuracy of the opening. Therefore, considerable accuracy is required in this regard. Studies have shown that more than 50% of the rock hole offset is due to unreasonable propulsion beam adjustment and poor opening.

4. Stability of the hole

Another requirement for the drilled hole is to remain stable until it has been used for dosing or other purposes. Under certain conditions, such as when drilling loose materials or soft rock zones (where there is a tendency to de-form and block rock holes), it is important to use drill pipes or hoses to run along the drilled rock holes.