DTH Drilling Advantages and Applications

Down-the-hole drilling (DTH) essentially involves a drilling hammer at the bottom of a drill string. It relies on three elements for drilling holes: bit loading (weight), rotation, and air. These active elements combine to be efficient at crushing rock. As the drill string slowly rotates, the drilling hammer is forced into the rock repeatedly. Striking power is provided by compressed air driving a piston inside the hammer.

DTH drilling advantages

DTH drilling offers several advantages over top-hammer drilling for larger, deeper holes in medium-hard formations. Because the hammer is at the bottom of the hole, power loss is minimal as the hole deepens. That means energy is not lost in the drill string and penetration rates do not markedly decline with depth—provided that backpressure does not rise significantly in the borehole. DTH drilling is most suitable for hole diameters of 4–10 inches, with some exceptions.

Compressed air power

The DTH hammer is pneumatically powered, with the compressed air propelling it forward to impact and fracture the rock. Compressed air also travels through the drill bit into the hole (air exhaust), which blows the chips and dust out of the hole.

Quieter drilling

From environmental and social perspectives, DTH is a good option because it produces much less noise and vibration than many other drilling methods. Quieter drilling means it is often the preferred drilling method when used in cities and populated areas.

DTH drilling Applications

The essence of submerged rock drilling is to make the impactor submerged in the hole during the drilling process in order to reduce the energy loss due to the impact work transmitted by the brazing rod, thus reducing the impact of the hole depth on the drilling efficiency. The rock drilling equipment for submerged rock drilling is a submerged drilling rig, which is an impact rotary drilling rig with an internal structure different from that of a general rock drilling rig, with its gas distribution and piston reciprocating mechanism is independent, i.e., the impactor. The front end is directly connected to the drill bit and the rear end is connected to the drill pipe. When drilling, the impactor is submerged in the hole, and through the air distribution device (valve), the piston (hammer body) in the impactor reciprocates and strikes the braze tail, which makes the drill bit impact the rock at the bottom of the hole. The high-speed rotation of the impactor in the hole is achieved by a separate rotation mechanism, i.e. by an electric motor or wind-driven rotating device outside the hole, through the drill pipe connected to the back end of the impactor. The rock powder produced during rock drilling is flushed out of the hole by the wind-water gas mixture, which is injected into the impactor through the center of the drill pipe by the powder discharge mechanism, and then enters the bottom of the hole through the gas slot on the impactor cylinder.

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