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A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. Tunnels are excavated through hard rock, wet or dry soil, or sand , each of which requires specialized technology.
A rotating cutting wheel is located at the front end of the shield. Behind the cutting wheel there is a chamber where the excavated soil is either mixed with slurry (so-called slurry TBM) or left as-is (earth pressure balance or EPB shield), depending on the type of the TBM. The choice of TBM type depends on the soil conditions.
Tunnel Construction. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk management.
The Stormwater Management And Road Tunnel (SMART Tunnel), E38, is a storm drainage and road structure in Kuala Lumpur, Malaysia, and a major national project in the country. The 9.7 km (6.0 mi) tunnel is the longest stormwater drainage tunnel in Southeast Asia and second longest in Asia .
The decision whether to construct a tunnel using a TBM or using a drill and blast method includes a number of factors. Tunnel length is a key issue that needs to be addressed because large TBMs for a rock tunnel have a high capital cost, but because they are usually quicker than a drill and blast tunnel the price per metre of tunnel is lower. [ 2 ]
Its products have often pushed technological boundaries; a Herrenknecht-built TBM in the late 1990s was the largest in the world at that time, while the world's longest and deepest railway tunnel (the Gotthard Base Tunnel) was bored using the company's apparatus. By 2015, the company had around 5,000 employees.
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Construction work in 2010. The Niagara Tunnel was constructed using a Tunnel Boring Machine (TBM), affectionately named "Big Becky" in honour of Sir Adam Beck.The TBM machine bored a tunnel about 10.2 kilometres (6.3 mi) long and about 14.4 metres (47 feet) in diameter under the City of Niagara Falls, Ontario, from the Niagara River to the SAB complex.