To gather geological or hydrological information, or to perform tasks like construction, mining, or engineering projects, drilling machinery is commonly employed to bore holes into soil or rock layers. We will break the bottom of the hole rock methods and technical measures of the general term called the drilling method. Within the drilling domain, various methods exist, each boasting distinctive advantages and outcomes.
What are the drilling methods?
In all kinds of drilling machinery drilling, the main drilling methods are shelf rock drill drilling, rotary drilling, and DTH hammer drilling.
Shelf rock drill drilling
It is generated by the pneumatic or hydraulic rock drill on the drilling frame outside the hole and transmitted to the rock through the shank adapter, coupling sleeve, drill rod, and drill bit. When the energy breaks the rock, the rock slag is blown out through the fine holes in the drill rod by the supplied pressurized air.
Rotary drilling
It is provided with torque and shaft pressure by the rotary mechanism and pressurizing mechanism outside the hole, the drill bit breaks the rock under the action of shaft pressure and torque, and the rock slag is discharged out of the hole by compressed air.
DTH hammer drilling
In this method, there is only a rotary mechanism outside the hole. The DTH hammer is located at the end of rock drilling tools. The DTH hammer directly impacts the drill bit to break the rock. The power medium drives the hammer and discharges the rock slag out of the hole.
Among the above drilling methods, DTH hammer drilling has been widely recognized and adopted by the industry due to its many significant advantages.
Advantages of DTH hammer drilling
Wide range of uses
DTH hammer drilling is not only widely used in open-pit mining, underground mining, and quarrying work but also widely used in water well drilling, mineral exploration, engineering geological exploration, pile hole drilling, rock stratum reinforcement, geothermal hole drilling, ground anchoring and installation of communication lines and drainage pipelines.
The through-type DTH hammer with double-wall drill pipe for reverse circulation continuous core drilling, is used in mineral exploration, engineering geological exploration, and other fields. It effectively solves the problem of difficult drilling, coring, and wall protection in complex formations such as sand, pebbles, gravel, difficulty, high cost, long cycle, and other problems. This kind of drilling, used for drilling hydrological water wells, can fundamentally solve the problems of slag removal, coring, orifice pollution, rock slag blocking the aquifer and affecting water output, etc., and raises drilling technology to a new level.
The DTH hammer is suitable for the construction of anchors in soft strata. It implements the impact and compaction hole-forming method without excavation. It has high drilling speed, good directionality, and regular hole walls, which is beneficial for anchoring and pressure grouting, and it is especially suitable for anchoring projects with high precision requirements.
Use a DTH hammer with an eccentric drill bit or a center reaming drill bit to follow the pipe drilling so that the complex collapse-prone hole drilling wall protection and hole synchronization is completed.
Good adaptability
Shelf rock drills drill into soft rock and broken rock formations and are prone to stuck drill bits. The cost will increase when drilling equipment is worn or damaged in hard rock. When rotary drilling encounters hard rock formations, the drilling speed drops rapidly, and the consumption of drill bits increases, which significantly increases the cost. Although the drilling speed of the DTH hammer is also related to the rock hardness, it is suitable for all rock formations except very soft ones.
Wide range of drilling sizes
Because of the limited power of the shelf rock drill and the high loss in the energy transfer process, the drilling size is generally less than 115 mm. During rotary drilling, the bearings of small drill bits are prone to early damage, so the hole diameter is usually no less than 165 mm. With the successful development of different types of DTH hammers, DTH hammers can drill holes of various sizes.
Drilling on various sites
Rotary drilling generally cannot work in sites with poor conditions due to its large rotation, pressurization, and other mechanisms. However, the DTH drill has a simple rotary and pressurizing structure and a low center of gravity. Therefore, it can work safely in poor conditions.
Fast drilling speed
Generally speaking, the drilling speed of a DTH hammer is faster than that of other drilling methods.
The drilling energy of a shelf rock drill is consumed during the transfer of force in the shank adapters, drill rods, coupling sleeves, and drill bits, so the drilling speed decreases as the depth of the hole increases.
The drilling speed of rotary drilling is relatively fast in soft rock, but as the rock hardens, the drilling speed will drop rapidly.
The drilling speed is also slower when using low-pressure DTH hammer drilling. In recent years, with the widespread application of high-pressure DTH hammers and the successful development of high-pressure water-driven DTH hammers, the drilling speed of DTH hammers has become faster and faster. In hard rock, DTH hammer drilling speed is comparable to that of rotary drills. The advance speed is more than doubled and does not decrease as the hole depth increases.
Straighter holes
Since the DTH hammer drilling system is rigid, the hammer is only slightly smaller than the drill bit, and drilling with the DTH hammer does not require high axial pressure like rotary drilling, and high axial pressure can easily cause drilling deviation. It also does not have as much impact energy from the surface as a shelf rock drill. Therefore, the hole is straighter and has good neutrality.
Drilling cleanliness
Because DTH hammer drilling uses high air pressure or high-pressure water as the power medium, the power medium can also flush the borehole well after driving the hammer to break the rock, keeping the bottom of the hole clean, thus eliminating the possibility of over-drilling. Rotary drilling and shelf rock drill drilling usually use low air pressure or a gas-water mixture to flush the borehole, which is generally difficult to clean.
In brief, Down-the-Hole (DTH) hammer drilling stands out as a highly efficient and precise drilling technique. It boasts broad applicability, user-friendly operation, and noteworthy traits such as high efficiency and speed. These characteristics provide strong technical support and guarantees for various projects. As science and technology advance, the methods of DTH hammer drilling will persist in evolving and enhancing, delivering even more top-notch and efficient services for geological exploration, engineering construction, and various other fields.
