A RELIABLE CONVEYOR
MAINTENANCE SPECIALIST
MAINTENANCE SPECIALIST
Tunnel construction should always be judged on how effectively it has succeeded at its stated aims, balancing the problem it was intended to solve with the cost of construction equipment.
The infrastructure world was radically revolutionised by the invention of the tunnel boring machine (TBM), but what is often misunderstood or underappreciated is the vital importance of robust conveyor belts to the ways in which they function.
To explore why, it is important to know how TBMs work, what conveyor belts do in tunnel construction, and why keeping your belts running keeps your project running.
A tunnel boring machine, also known as a TBM or mole, is a dedicated, specialised, typically cylindrical machine used to excavate huge tunnels as efficiently as possible.
Whilst early prototypes were used as early as Mark Isambard Brunel’s Tunnelling Shield of 1818 to construct the Thames Tunnel and were used throughout the 19th century, tunnel boring machines were increasingly used in the latter half of the 20th century.
Today, they are the most common way to build tunnels over 1.5 miles long, as by this point the efficiency benefits of using a TBM offset the initial fixed costs of designing a custom-made machine for the soil, rock and spoil you are drilling into.
A TBM creates smooth tunnel walls that can be easily and affordably lined. Some TBMs even establish lining and reinforcement as part of their design.
Efficiency and integration are their key advantages, but the only way to make the most of this is with the help of a dedicated, robust, and well-designed conveyor belt system.
A TBM is only as efficient and economical as all of the systems built around it, and whilst they can very effectively cut into a rock and move vast quantities of earth, all of that spoil, muck and mire needs to go somewhere.
Part of this is often integrated into the TBM itself, but it connects to a series of trailing conveyors known as the backup system. These directly connect to the TBM and stretch throughout the entirety of the tunnel system as it is excavated.
These carriages and decks help in the first, vital part of safely moving spoil away from the tunnel itself, which reduces the risk of muck clogging the machinery which makes up a tunnel boring machine.
It also allows for the next essential step, which is moving waste material to a sorting station where it can be filtered, sorted and organised for later reuse.
This can sometimes be done using trollies or trucks, but it is common for a belt conveyor connected to a TBM to be then connected to a network of conveyor belts that continue to move spoil and ground-up rock where it needs to go.
Given the vital importance of reusing waste materials that are produced as a consequence of vast underground earthmoving projects, conveyor belts have become more essential than ever before.
Conveyor belts are used in all kinds of tunnel construction, but they are fundamentally integral in several types of tunnel boring machine, even outside of highly efficient waste management.
Commonly used in urban areas to safely create smooth, efficient tunnels, a Slurry Pressure Balance (SPB) TBM fills the working chamber just behind the cutter with slurry, which mixes with the clay, soft sand or other relatively unstable material in order to easily and safely tunnel and move spoil away.
Conveyor belts are a vitally important part of this method, as they help quickly move the wet slurry and soil away from the machine once they have mixed together. It needs to be efficient for the process to work safely.
A slurry-less version of the SPB TBM, an Earth Pressure Balance (EPB) TBM primarily relies on a screw conveyor system to move spoil away from the base of the cutter.
This system also relies on an additional conveyor system at the top of the screw conveyor to move spoil further from the machine and towards a more conventional material removal system.
Consisting of a hugely powerful crusher and cutter heads, a hard rock TBM is designed to slice rock into pieces that can be safely moved further down the range.
Conveyor belts are needed to move the crushed stone and gravel through the TBM shield and towards the waste management system at the base of the tunnel.