3 ms·

Why is the upfront cost bigger for TBMs? If the TBM can be used on any length of tunnel, can't you resell it afterwards, or rent it instead of buying?

CompelTechnic 9y ago
(just a guess) even if you are only using it for a small fraction of its lifetime, you are amortizing the cost of a large piece of capital equipment, so the upfront cost must take this into account. Blasting has a smaller investment in capital equipment (even if amortized similarly) There is also the setup- carting in the pieces of the TBM and getting them into place, etc.
masklinn 9y ago
> Why is the upfront cost bigger for TBMs? Because a TBM itself is a large capital investment. A small TBM (~7m diameter) is ~10m€, a large TBM probably reach 100m€. This is money you have to pay upfront before the TBM even reaches the dig. The capital investment of D&B is a (few) jumbos which are cheaper (even large and expensive jumbos are unlikely to breach 2m€ brand new), more flexible (they're also used in mining operations) and less dependent of the manufacturer — thus easier to rent or buy used. > can't you resell it afterwards, or rent it instead of buying? The "back end" (gantries) can be sold back to the builder and refurbished, the "front end" (shield and cutter head) is thrown away (some are used as monuments) or recycled: https://www.herrenknecht.com/en/services/global-services/tbm-refurbishment.html https://www.herrenknecht.com/en/services/global-services/tbm... That's still expensive as hell, and you've still sunk the money in until the builder has examined and bought back the gantries after the project has ended.
Someone 9y ago
TBMs are designed at a specific diameter, for the kind of soil to bore through, wear down quickly, and aren’t easily moved. It often isn’t worth it to take apart a TBM and reconstruct it elsewhere, even if you could find a customer wanting a tunnel of the same width through similar soil. For long tunnels, it isn’t uncommon to have two TBMs that meet in the middle and are abandoned there (they bore a side tunnel long enough to contain the TBM, and the side tunnel is closed behind them) For example, see https://untappedcities.com/2017/02/09/the-200-ton-tunnel-boring-machine-buried-below-park-avenue-used-for-east-side-access/ https://untappedcities.com/2017/02/09/the-200-ton-tunnel-bor...: ”Burial of such a large machine was unprecedented in New York City, but is common practice abroad, reported the New York Times in 2011. The Spanish contracting company working on the project deemed it would be more cost effective to leave Seli in place. It was estimated that removal would cost millions and cause delays in existing construction projects. Dr. Michael Horodniceanu, the president of MTA Capital Construction, estimated at the time it would cost $9 million to remove Seli, which had cost somewhere between $6 to $8 million new.”
donarb 9y ago
In Seattle's underground tunnel, the TBM was delivered from Japan along the waterfront close to its starting point. It was assembled, then lowered into the pit. At the tunnel exit is a highly congested maze of streets. In order to remove the TBM, the 2000 ton cutter head needed to be cut into pieces that would not weigh more than the city's 20 ton weight limit for streets. With Seattle's design/build contract, the construction company owned the TBM. To them it's just a tool whose cost is part of the construction package.

CompelTechnic 9y ago

(just a guess) even if you are only using it for a small fraction of its lifetime, you are amortizing the cost of a large piece of capital equipment, so the upfront cost must take this into account. Blasting has a smaller investment in capital equipment (even if amortized similarly) There is also the setup- carting in the pieces of the TBM and getting them into place, etc.

masklinn 9y ago

> Why is the upfront cost bigger for TBMs? Because a TBM itself is a large capital investment. A small TBM (~7m diameter) is ~10m€, a large TBM probably reach 100m€. This is money you have to pay upfront before the TBM even reaches the dig. The capital investment of D&B is a (few) jumbos which are cheaper (even large and expensive jumbos are unlikely to breach 2m€ brand new), more flexible (they're also used in mining operations) and less dependent of the manufacturer — thus easier to rent or buy used. > can't you resell it afterwards, or rent it instead of buying? The "back end" (gantries) can be sold back to the builder and refurbished, the "front end" (shield and cutter head) is thrown away (some are used as monuments) or recycled: https://www.herrenknecht.com/en/services/global-services/tbm-refurbishment.html https://www.herrenknecht.com/en/services/global-services/tbm... That's still expensive as hell, and you've still sunk the money in until the builder has examined and bought back the gantries after the project has ended.

Someone 9y ago

TBMs are designed at a specific diameter, for the kind of soil to bore through, wear down quickly, and aren’t easily moved. It often isn’t worth it to take apart a TBM and reconstruct it elsewhere, even if you could find a customer wanting a tunnel of the same width through similar soil. For long tunnels, it isn’t uncommon to have two TBMs that meet in the middle and are abandoned there (they bore a side tunnel long enough to contain the TBM, and the side tunnel is closed behind them) For example, see https://untappedcities.com/2017/02/09/the-200-ton-tunnel-boring-machine-buried-below-park-avenue-used-for-east-side-access/ https://untappedcities.com/2017/02/09/the-200-ton-tunnel-bor...: ”Burial of such a large machine was unprecedented in New York City, but is common practice abroad, reported the New York Times in 2011. The Spanish contracting company working on the project deemed it would be more cost effective to leave Seli in place. It was estimated that removal would cost millions and cause delays in existing construction projects. Dr. Michael Horodniceanu, the president of MTA Capital Construction, estimated at the time it would cost $9 million to remove Seli, which had cost somewhere between $6 to $8 million new.”

donarb 9y ago

In Seattle's underground tunnel, the TBM was delivered from Japan along the waterfront close to its starting point. It was assembled, then lowered into the pit. At the tunnel exit is a highly congested maze of streets. In order to remove the TBM, the 2000 ton cutter head needed to be cut into pieces that would not weigh more than the city's 20 ton weight limit for streets. With Seattle's design/build contract, the construction company owned the TBM. To them it's just a tool whose cost is part of the construction package.