Search results
Results from the WOW.Com Content Network
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.
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 ]
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.
Freighter Fairpartner carrying the disassembled tunnel boring machine into the Port of Seattle in April 2013. Bertha was designed and manufactured by Hitachi Zosen Sakai Works of Osaka, Japan, and was the world's largest earth pressure balance tunnel boring machine, [14] at a cutterhead diameter of 57.5 feet (17.5 m) across.
The $80 million tunnel boring machine (TBM) Bertha was created for this project by Hitachi Zosen Corporation near Osaka, Japan. The 326 ft (99 m), 6,700-short-ton (6,100 t) TBM was disassembled into 40 pieces and shipped to Seattle, where it was reassembled in the launch pit near the south end of the future tunnel. [63]
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
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.