The invention of the tunnel boring machine has had a profound impact on the tunneling industry around the world. The speed, safety and efficiency of the machines have allowed tunnels to be built throughout the world in varying geologies for a variety of civil purposes, as well as mining, military, research and other uses.

But the TBM itself is only part of the equation. The best TBM design is limited by the ability to move spoil from the cutting face out of the tunnel. Early TBMs relied solely on muck cars to move excavated material from the face. When belt conveyor were introduced, however, the speed and efficiency of the machine greatly increased.

What are the advantages of belt conveyor systems?

As TBMs were being developed, manufacturers did a lot of work so that the machines could mine faster and more efficiently. However, they were restricted by the ability to get material out of the tunnel, especially as the tunnels became longer and longer. With rail haulage, you end up having to wait for locomotives, you have to set up switches, and there can be issues with locomotives getting derailed. Additionally, you need to upsize your ventilation if you are dealing with diesel locomotives. With the belt conveyor system, the only time tunneling stops is to add belt. Once the belt conveyor systems were introduced, we started to see TBMs around the world breaking speed records.

What is the rule of thumb for deciding between a belt conveyor and muck cars?

It is always the contractor’s decision, but generally if the tunnel is a mile or more in length, conveyors are used. If it is shorter, then muck cars will probably be used. But that is changing. Over the past decade or so belt conveyor systems have been built for more efficient setup and can allow the contractor to start mining more quickly vs. a muck car arrangement. This is because the components themselves are modular, making for easier shipment and installation.

How do you get the most out of your belt conveyor system?

Like many other pieces of equipment, maintenance is the key. It is particularly challenging with a belt conveyor system because it can stretch for miles and you can’t see the entire system at one time. But if you have one bad idler or one weak point in the system, the entire belt is going to cross it. There have been improvements with electronic monitoring to help the operator see what is going on with the system. Planning is also key, in the early stages of the project, there is a lot of belt strength and power in the system, but as the belt extends farther and farther, the load on the system increases.