The different types of raise boring
Raise boring has been revolutionising the mining industry since the 60’s and as with any new concept that has been given enough time to evolve, raise boring has undergone numerous changes. Today we are looking at 4 different types of raise boring that have the ability to suit a number of shaft creation needs.
These are the 4 types of modern raise boring methods that can be used with an industry specific machine.
1. Conventional raise boring
Of all the types of raise boring, this is the most common method to use. Conventional raise boring uses a raise drilling machine to drill between two levels in order to create a vertical shaft. On the upper level of the shaft a pilot hole is drilled before the drill bit on the machine is changed to a reamer head which is used to drill the rest of the hole between the two levels. The reamer bit is strong enough to drill all the way down into the next level of the mine. The debris left over from the drilling will fall to the floor of the level below, gravity pulling it down. From there it can be easily collected and swept away.
Conventional raise boring can be used in just about any mine. Most of the time the shaft is created for the purpose of ventilation or for the purpose of moving machinery and people into and out of the mine.
2. Down reaming
Just like the conventional drilling, down reaming is done vertically from the upper level into the bottom level. Once the shaft is drilled right through the drill bit is brought back up to the surface. This is not usually done with conventional raise boring as first a pilot hole is usually drilled, something that is missing from this method of raise boring. Once the drill bit comes back to the surface, the reamer is attached and the hole is made smooth and even. This method of raise boring is ideal when there is little space below for the reamer to push through the earth.
Like the conventional raise boring method, the materials that are removed by the drilling process will fall onto the floor of the lower level and from there they can be collected and removed. The process can be completed quickly and without too much fuss.
3. Blind hole drilling
The two methods discussed above concern raise drilling that is done from top to bottom, from the top level of the mine through two levels and into a bottom chamber. The method of blind hole drilling is done the opposite way, with the hole being drilled from the bottom up. The raise drilling machinery is placed on the lower levels and from there the machine drills a hole into the level above it.
This type of drilling combines the drilling of the pilot hole and the shaft itself as the process is not stopped to accommodate the attachment of a reamer drill bit. Anything that is drilled away will fall to the ground below where it will be collected and removed from the lower level of the mine.
4. Horizontal raise boring
While the other methods of raise drilling are concerned with the shaft being drilled vertically from the top of the shaft to the top (or from the bottom to the top), this method of raise drilling is done by drilling the shaft horizontally. This is pretty much the only difference between the two methods, as a pilot hole will still have to be created and then a reamer bit attached to drill the actual shaft.
This different type of drilling is done for the placement of horizontal pipes which means it is not necessarily done for mining purposes but can be used in a number of other industries.
A quick mention of the uses of raise drilling
As a commonly used form of drilling, raise boring has more uses than you’d think. The most common use of raise boring is for ventilation purposes. Mines need a constant supply of fresh air and once the air is pumped into a mine it needs a place to escape from. Shafts are built for this purpose. Sometimes the shaft can have a pipe system fitted which will pump the air into and out of the mine.
Alongside pumping air into the mine, drainage is another important purpose that raise boring can fulfil. Water is used a lot in mining. It is used during many of the mining steps or it can be used to flush out any rock that has not been moved away yet. Water is also the key role player in hydraulic mining (which is the mining of sediment deposits which are flushed through a sluice box to remove the mineral deposits).
The removing of minerals after they are mined is the most important part of mining. And how else can this be done if there is no passage for the minerals to be easily removed from? Raise boring is used to create the important shafts that will be used to remove the deposits from the mine. And while we are on the topic of removing things from the mine, the miners themselves and their machinery can also be easily removed from the mine when a shaft has been created.
Raise boring has revolutionised the way in which mining is done and in many ways it has simplified the process and made the industry a whole lot safer.