Revolutionizing Stope Mining: A Comprehensive Guide

What is a Stope in Mining?

A stope is a dugout tunnel or space that contains the ore that is being mined. Clear stopes are essential for a mining industry operation to run smoothly.

The stope provides direct access to the orebody and routes ore and waste in an underground mine. Stopes are created by drilling holes, placing explosives, and blasting open a space, which produces a stope.

Clearing a tunnel

Considerations for Creating Stopes

When creating stopes, it is common practice to dig vertical shafts down to the orebody. Once the ore is reached, horizontal levels are created to mine the ore. These levels are where stoping occurs.

When creating a stope, miners consider the following:

The grade of the ore
The width of the ore
The incline of the ore (tilted, vertical, or flat)
The strength of the surrounding rock
The cost for supporting the mine roofs

Depending on the orebody orientation, an underground mining technique will be selected to extract the greatest amount of ore from a stope.

Underground Mining Techniques

When the orebody orientation is horizontal, cut and fill stoping, room and pillar stoping, and longwall mining are mining techniques that can be used to extract the ore.

Each technique includes building ramps and drifts. Ramps are inclined tunnels that start from the surface of the mine and connect to mining levels. These levels where mining takes place are called drifts.

Cut and Fill Stoping

Cut and fill stoping is a mining technique that starts mining operations from the bottom of an orebody vein and works up towards the surface of the mine.

Miners use explosives at the bottom-most level of the vein to loosen the orebody. The blasted ore deposits are then funneled to ore passes and transported outside of the mine. After the ore has been depleted on one level, the stope is backfilled and miners move up to the next level, working their way up until the mine is completely depleted.

Room and Pillar Mining

Also called stope and pillar mining, room and pillar mining involves mining stopes to gain access to mining the ore.

Loaders and haulers transport loose rock out of the mine. Stopes are cut into the ore body, leaving pillars in place to support the roof of the mine. In most instances, a roof bolter will also be used to help support the roof.

Once the ore has been extracted from the stope, pillars will be removed with extreme caution to extract the maximum amount of ore from the room. Depending on the rock conditions, this pillar removal can sometimes create planned cave-ins.

Room and pillar mining

Longwall Mining

Longwall mining is commonly used to extract coal.

Once the ramp and drifts are excavated, a longwall mining machine, called a shearer, is used to mine coal from the coalface. Hydraulic jacks support the roof while the shearer moves down a conveyor belt of up to 400m in length alongside the coalface, extracting coal.

Sublevel Caving

Sublevel caving is a progression to underground mining after an open-pit mine is depleted of ore.

Tunnels are created under the open-pit. Then, the drill and blast method is used to connect the open pit to the underground network. Rock from the surface mine caves in, then loaders and haulers transport the materials to an ore pass, where the rocks are lifted to the surface up a shaft in an elevator bucket, called a skip.

This cave-in process continues deeper into the mine until the ore is completely depleted from the top down.

Sublevel Stoping

Sublevel stoping is a mining technique in which ore is blasted from the roof of a drift directly into an ore pass below.

Loaders and haulers transport the ore and loose rock to another ore pass, which funnels it into a hopper. The hopper controls how much material is allowed into the crusher. After rock is crushed, the skip takes the material up an elevator shaft to the surface of the mine.

The drift is blasted further and further up the mine, repeating this process until another jumbo drill has to intersect the blasted stope. Once the ore is completely excavated, the stope is backfilled.

Stoping Methods

Before blasting, an initial slot must be present to successfully extract the ore. A slot is the basis for creating the stope. The following are methods used to create a slot hole:

Raise bore. A raise bore is the bottom-up construction of a cylindrical shaft that is created by using mechanical rollers. This is a good technique when longer stopes are needed.
Longhole raise. A longhole raise (also called longhole stoping) is a series of smaller blast holes that are drilled either down or up. This is a good technique when shorter stopes are needed.
Airleg raise. An airleg drill is versatile and can be used to determine the condition of the rock before mining.
Boxhole boring machine. Boxhole boring machine creates slot holes with small diameters. This is similar to a raise bore, but differs in that the broken materials are extracted directly from the drill site.

Airleg raise

Long-Hole Stoping

Long-hole stoping is one of the most common ways to create stopes in a mine. This method drills preprogrammed holes up towards the surface. Explosives are planted and the hole is blasted. This is a highly automated and mechanical process.

Once the stope is blasted, it cannot be accessed by personnel, so blasted rock is designed to fall directly to a drawpoint.

Shrinkage Stope Mining

Shrinkage stoping moves from the bottom up, similar to cut and fill underground mining.

Shrinkage stope mining is used for steep bodies of ore, with 60% of the broken ore left in place for miners to work through. (The other 40% is removed in order to prove adequate working space for the miners to access the next ore slice.)

Once the ore is depleted from the bottom up using shrinkage stope mining, the mine may be backfilled depending on the rock conditions inside.

Drilling from the bottom up

Timbered-Stoping

Timbered-stoping uses timber to support the stope and to prevent cave-ins. Miners will also use the timber to work from, like makeshift scaffolding.

There are two types of timbered-stoping:

Square-set stoping. Square-set stoping uses timber that is set into stopes in a square pattern. This is then backfilled with tailings, or mining waste, and a binder like cement.
Stull stoping. Stull stoping uses seemingly random timbering, called stulls. The stulls are placed between the foot and hanging wall of the ore vein. Stull stoping is used in mines with strong rock support since the stulls don’t provide much structural support. Backfilling these stopes made by stull stoping with large voids can be extremely dangerous and can cause a mine to collapse.

Open Stope Mining

The open stoping mining method is unique in that it does not require artificial support.

There are four types of open stope mining:

Overhand stoping. Overhand stoping is an open stope mining method that works the ore deposit from the bottom upward. With the drill and blast technique, this is the typical direction used to create a stope.
Underhand stoping. Underhand stoping is an open stope mining approach that works the ore deposit from the top down and is used in cut and fill underground mining. This method was more widely used when miners predominantly used hand tools and could rely on gravity to collect ore.
Combined stoping. Combined stoping is an approach to open stoping that works the ore deposit from the top and bottom simultaneously.
Breast stoping. Breast stoping is an open stope mining method that works the horizontal orebodies. The breast stoping method is best used in stope and pillar mining.