How much does a tunnel bore machine cost? The cost of a tunnel boring machine (TBM) varies widely depending on factors such as its size, the complexity of the project, and the machine's specifications. A commonly cited estimate is approximately $1 million per meter of the machine's diameter. For instance, an 8-meter diameter TBM would cost around $8 million.

　　Here are some general price ranges:

　　Small TBMs (e.g., for utility tunnels):

　　Diameter: 1-3 meters (3-10 feet)

　　Cost: $1 million to $10 million

　　Medium-sized TBMs (e.g., for metro or road tunnels):

　　Diameter: 4-8 meters (13-26 feet)

　　Cost: $10 million to $50 million

　　Large TBMs (e.g., for large infrastructure projects like water tunnels or rail tunnels):

　　Diameter: 9-15 meters (30-50 feet)

　　Cost: $50 million to $100 million+

　　These costs cover just the machine itself. Additional expenses include:

　　Operation and maintenance: Running the machine, replacing cutter heads, and lubrication.

　　Logistics: Transporting and assembling the TBM at the site.

　　Customization: Designing the TBM for specific geological conditions (e.g., hard rock, soft soil, or mixed ground).

　　However, this is a general guideline, and actual costs can differ. Smaller-diameter TBMs often cost less than $1 million per meter, while larger machines, especially those exceeding "subway size" diameters, can be more expensive due to increased technological complexity. For example, a 16-meter diameter TBM purchased by the Santa Clara Valley Transportation Authority for the BART Silicon Valley Phase II Project was priced at $76 million, significantly higher than the per-meter estimate.

　　In massive projects like the Gotthard Base Tunnel or the Channel Tunnel, TBMs can exceed $100 million due to their size and complexity.