This powerful machine weighs more than one thousand tons, and has to be activated by about five thousand kilowatts of electricity equivalent to that needed to light up five thousand light bulbs. In addition, each TBM and its components have to be tailor-made according to the diameter and anticipated geology to be excavated.

Apart from cut and cover and blasting, Tunnel Boring Machine (TBM) is a commonly used construction method in building tunnels nowadays. The type of tunnelling method to be used depends on the specific geology of the project, tunnel length or diameter, logistical arrangements, environmental and other factors.

With a large rotating steel cutter head at the front of the shield, TBMs can pass through different types of soil, rock or mixture of both. The TBM is a multi-functional construction tool, which can excavate and remove excavated materials, and at the same time install the reinforced concrete lining of the tunnel as it progresses. This method, unlike cut and cover excavation works, does not require disruption to the road surface during construction.