Additional Final Draft Reader Response

Designed to optimize performance while maintaining safety standards during underground excavation, Herrenknecht’s Multimode (MM) Tunnel Boring Machine (TBM) is an all-in-one, state-of-the-art engineering masterpiece. Herrenknecht MM TBM consists of the cutterhead, thrust system, and screw conveyor (Herrenknecht, n.d., Multimode TBM). Firstly, the cutterhead excavates the soil or rock. Secondly, the thrust system moves the TBM forward while tunnelling. Lastly, the screw conveyor conveys the debris from the cutterhead to the back of the TBM for removal. The MM TBM can operate on various geological conditions, including soft ground, heterogeneous ground, and rock formations (Herrenknecht, n.d.). According to the same webpage, two key features are its modular structure and integrated systems. The functions of these features allow clients to modify components in a relatively short time and at a lower cost when facing complex geological conditions. Additionally, the integrated system enables the client to seamlessly swap to different modes, which include Earth Pressure Balance, Open-face and Slurry TBM mode (Herrenknecht, n.d.a, One basic idea two concepts section, para. 4).

Herrenknecht’s MM TBM revolutionizes tunnel construction through enhanced efficiency and adaptability to diverse geological conditions compared to traditional alternatives such as Underground Infrastructure Technologies (UIGTEC) TBM. However, challenges such as high costs and operational complexities must be addressed to maximize long-term accessibility and sustainability in global infrastructure projects.

The Herrenknecht MM TBM revolutionizes tunnel construction while improving efficiency. It does so by eliminating the need for multiple machines, reducing downtime, and optimizing excavation across varying geological conditions due to Herrenknecht MM TBM integrated system. For example, in the Klang Valley MRT Project, with Herrenknecht MM TBM’s integrated system, the engineers involved in the project were able to combine the advantages of Earth Pressure Balance (EPB) and slurry mode with only minor modifications (Chapman et al., 2017). This combination was used to prevent loss or leak of bentonite slurry into the ground by being able to control the density of the medium. Hence, this enhances efficiency in excavation work and diminishes costs for having several TBMs as it simplifies the tunnelling work (Chapman et al., 2017). In contrast, UIGTEC TBMs, do not have a single TBM that is as efficient as Herrenknecht’s MM TBM when faced with challenging geology that usually requires more than different types of TBM (Underground Infrastructure Technologies, n.d.). By offering a versatile integrated system, Herrenknecht MM TBM enhances efficiency for work done thus making it the ideal solution for infrastructure projects.

The Herrenknecht MM TBM also offers superior adaptability, allowing seamless transitions between different geological conditions due to its modular feature. A Herrenknecht MM was used in Paris to tunnel through various geological conditions such as clay, limestone, and three different groundwater levels (Chapman et al., 2017). In contrast, each UIGTEC TBM mainly depends on the geological conditions of the project (Underground Infrastructure Technologies, n.d.). This means that, unlike Herrenknecht MM TBM, UIGTEC does not offer a TBM capable of adapting to different geological conditions. Hence, Herrenknecht MM TBM provides unmatched adaptability, making it the top choice for complex infrastructure that spans multiple conditions.

High procurement costs and the requirement for specialized operators are some challenges facing the Herrenknecht TBMs. Herrenknecht TBMs typically cost between US$5 million to US$30 million, depending on the machine’s specifications (Charter Capital, 2022, Tunnel Boring Machine Cost section).  In some large-scale projects, such as the BART Silicon Valley Phase 2 Project, a Herrenknecht TBM was procured for US$76 million (Valley Transportation Authority, 2023, para 1). Furthermore, the high level of automation and specialized training for operators increases labour costs (Herrenknecht, n.d., Utility Tunnelling Customer Training). Conversely, the traditional drilling and blasting method is cost-effective for smaller tunnelling projects. For example, the average cost for drill and blast is roughly, SGD$1,229.08 for a project tunnel cross-section that ranges from 10 square meters to 120 square meters (Zara & Bruland, 2007). However, despite its lower initial cost, it poses greater risks, including environmental damage, slower excavation rates, and higher labour requirements, making it unsuitable for large-scale urban projects. While the initial purchase of Herrenknecht TBMs is expensive, the long-term cost is justified by their efficiency, safety, precision, and reduced operational costs in large-scale projects.

With the introduction of Herrenknecht MM TBMs, tunnelling technology is forever changed in the spheres of efficiency and adaptability to different geo-conditions. With the changes in the world of technology like the increase in automation and more advanced AI-driven excavation, modular TBM designs are anticipated to improve. As this happens, Herrenknecht TBMs are projected to lead the industry in sustainability, infrastructure expenditure, and global automation.

(I hereby acknowledge the use of ChatGPT for error checking and sourcing of information for this Reader’s Response)

References:

Chapman, D., Metje, N. & Stark, A. (2017). Introduction to Tunnel Construction (pp. 157). CRC Press.
https://doi-org.singaporetech.remotexs.co/10.1201/9781315120164

Charter Capital. (2022, November 15). How much does a tunnel boring machine cost. 
https://charteraz.com/2022/11/15/how-much-does-a-tunnel-boring-machine-cost/

Herrenknecht. (n.d.a). Product detail: Multimode TBM.
https://www.herrenknecht.com/en/products/productdetail/multi-mode-tbm/

Herrenknecht. (n.d.b). Utility tunnelling customer training.
https://www.herrenknecht.com/en/services/transportation-and-jobsite-assembly/utility-tunnelling-customer-training/

Underground Infrastructure Technologies, (n.d.). Product catalog.
https://ugitec.co.jp/en/products/product-catalog/

Valley Transportation Authority. (2023, November 6). VTA purchases the tunnel boring machine for the BSVII Project.
https://www.vta.org/blog/vta-purchases-tunnel-boring-machine-bsvii-project

Zare, S., & Bruland, A. (2007). Progress of drill and blast tunnelling efficiency with relation to excavation time and costs. In J. Bartak, I. Hrdina, G. Romancov & J. Zlamal (Eds.), Underground Space – The 4^th Dimension of Metropolises (pp. 805 – 809). Taylor & Francis Group. 
https://doi.org/10.1201/NOE0415408073.ch133