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Raise Drilling

Raise drilling - large holes in two stages


In mining, connection of power plant tunnels or when channeling for electricity, telephone, gas or water pipes, etc, there is a considerable need to drill large holes. In these situations, Raise drilling is an exceptional alternative.

Raise drilling is used to create large drill holes – up to 7.6 metres in diameter. The holes, or tunnels, are used to connect mine shafts, power plant tunnels or channels for rainwater and surplus water, as well as for ventilation between different levels in a mine.

This type of drilling is performed in two stages. First you drill a smaller pilot hole and then you swap the smaller drill bit with a reamer. The reamer is equipped with reels made of hardened metal which have the same diameter as the final hole. The hole is expanded as the reamer crushes the rock using both pressure and rotation.

Raise drilling can be used for holes and tunnels of up to 1100 metres in length, which makes this method very practical for many applications.

Four different types of Raise drilling

Raise drilling can be performed in four different ways depending where the tunnel is and how it has to be shaped.

Conventional Raise drilling

The most common method involves drilling vertically, top downwards, from one mine level to another. First a pilot hole is drilled between the levels. When the drill bit has reached its destination a reamer is attached at the lower level and is then drawn back up the pilot hole. The rock residues fall back to the lower level where they can be transported away.

Down reaming

Another form of raise drilling is called Down reaming. This is also performed vertically and the drill rig is at the upper level. After the pilot hole is drilled from the surface to the lower level the drill bit is taken back up to the top level where the reamer is attached and then it is pressed downwards through the pilot hole. This method is used, for example, when space at the lower level does not permit the connection of a reamer.Blind hole raise drilling

In this method a hole is drilled vertically, from the bottom upward. The reamer is connected from the start, just below the pilot crown, and the larger hole is thus drilled at the same time as the pilot hole. The hole is drilled upward to the required height and does not ever need to reach a higher existing level. The crushed rock falls downwards and is collected in a special device attached to the raise drill.

Horizontal raise drilling

Raise drilling can be used to drill horizontal holes, such as holes for water, electricity or gas pipes. This method is similar to conventional raise drilling, i.e. a pilot hole is drilled first from one side to another. The reamer is then connected and taken back through the pilot hole to create a smooth horizontal tunnel.

Raise Drilling

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