Navigating the Depths: Raise Boring Tools for Deep Shaft Construction

Navigating the Depths: Raise boring Tools for Deep Shaft Construction

Navigate the challenges of deep shaft construction with Raise Boring Tools. This article examines how these tools are specially designed for deep drilling, addressing the unique demands of reaching substantial depths in mining and infrastructure projects.

raise boring methods

Pilot drilling

Conventional raise boring begins with the drilling of a pilot hole. It is drilled using a roller bit

with sealed bearings, together with hollow drill pipes 1.5 m in length with an international

standard thread for high–torque applications.

The cuttings are removed from the pilot hole with the aid of water flushing. Introduced

through the center of the drill string, the water flows out of the drill bit and up through

the annulus between the drill pipes and the hole wall. If required, the pilot drilling can be

controlled by using a directional drilling system.

Raise boring

When the pilot hole breaks through into the lower level, the roller bit is removed and replaced

with a reaming head. The reamer is rotated and pulled back toward the drilling unit. The

cuttings fall by gravity into the chamber at the bottom of the hole, where they are

mucked out using a LHD-type loader.

Raises up to 6 m in diameter and up to 1000 m in length are not uncommon. The raise-boring

method is used to produce ventilation shafts, ore passes, manways, penstocks etc.

Blind boring

When a raise is required but there is no access to the upper level, it has to be bored blind

from below, usually without a pre-drilled pilot hole. A special type of head is required for

blind boring. It drills the pilot hole and reams out the raise at the same time. The head is

rotated and pushed upward. The cuttings fall out of the hole by gravity.

Normal blind raise diameters are from 0.6 to 1.8 m. Since the drill string is under

compression during blind boring, special large-diameter stabilizers are needed to support

the drill string. The blind-boring method is used to produce so-called slot raises, ore passes

and manways.

Horizontal boring

Horizontal boring is an excellent method in urban construction projects where drilling and

blasting is restricted or forbidden and Tunnel boring machines (TBMs) are too bulky. First,

a horizontal pilot hole is drilled, with the aid of a directional drilling system if necessary.

When the pilot bit breaks through, it is removed and replaced with a reaming head. Because

the hole is horizontal, the reamer must be equipped with a special cuttings removal system.

Typical diameters for horizontal reaming are from 0.6 to 4.5 m. The method is used to

drill tunnels for cables, escape routes, sewage etc without disturbing the environment unduly.

Horizontal boring requires good rock stability.

Down boring with a pre-drilled pilot hole

In mines, large fill-holes between 0.6 and 1.8 m in diameter can be bored into stopes using

reaming equipment, provided that a pilot hole can be pre-drilled into the stope. The pilot

bit and drill string are then removed and a reamer fitted. The reamer is pushed and rotated

downward, guided by a nosepiece that follows the pilot hole.

The cuttings fall by gravity down through the pilot hole. Since the drill string is under

compression during down boring, special large-diameter stabilizers are needed to

support the drill string.