Spiral Decline & Mechanised Mining

Spiral decline and mechanised mining have transformed underground mining in recent decades. These methods are now widely used in leading gold-producing regions like Western Australia. They have made it possible to mine deeper, thinner, and lower-grade deposits efficiently and safely.

A spiral decline is a sloped, corkscrew-shaped tunnel that gives vehicle access from the surface to underground ore bodies. It removes the need for vertical shafts and hoisting systems. Trucks can drive in and out of the mine, carrying ore directly to surface. This makes operations faster, cheaper, and more flexible.

Mechanised mining methods—like sub-level open stoping—are used alongside spiral declines. These involve remote-operated loaders and precision drilling. Ore is mined along horizontal levels and removed using machinery, reducing manual labour and improving safety while allows for more consistent mining widths even in narrow veins.

The benefits are significant:

• Higher productivity – Mines can produce up to 10 times more ore per day than traditional shaft-based methods.
• Lower costs – Both capital and operating costs are reduced.
• Improved safety – Less manual handling lowers the risk to workers.
• Better access – Spiral declines allow continuous access to multiple ore zones.
• Scalability – These methods suit both small and large-scale mining.

Over time, Australia has refined these techniques to a high standard. In contrast, Zimbabwe remains heavily reliant on vertical shaft access. This approach limits efficiency and restricts the scale of underground operations. It is a legacy of historical underinvestment and limited access to modern mining equipment.

However, the potential is clear. Zimbabwe’s greenstone belts share many geological similarities with Western Australia. The same methods that have worked in Australia can be applied in Zimbabwe with the right investment.

Mining tunnels or ‘stopes’ are excavated in order to extract the ore. They are developed using a face drilling Jumbo, which is a mobile drilling machine that drills horizontal holes into the rock. The holes are then filled with explosives and fired, creating a muck pile of blasted rock. A specialised loader collects the rock from the face and places it in a stockpile. The stockpile is collected by another loader, placed in a truck, and transported to the surface.

A mesh is installed inside the tunnel by the Jumbo to make the tunnel safe. This is secured by steel rock bolts.

The main spiral decline access tunnel is positioned in waste rock adjacent to the ore body, and level horizons are developed off the decline into the ore body. The ore body or ore zone consists of a number of different narrow gold bearing shear zones which are intersected and followed by flat ore tunnel development.