Final answer:
The I-90 tunnels under the Railroad at South Station were built using advanced engineering techniques including diversion of obstacles, tunnel cutting, and reinforcement, reflecting the historical examples provided by the construction of the Hoover Dam and other infrastructure projects.
Step-by-step explanation:
The I-90 tunnels under the RR at South Station were likely constructed using advanced civil engineering techniques, similar to those outlined in the historical context given. While the exact methods for the I-90 tunnels are not detailed here, the construction of large-scale infrastructure during the 19th and 20th centuries demonstrates key principles and tactics. Specifically, the description of the Hoover Dam highlights the process of river diversion through tunnels, the use of cofferdams to create a dry construction site, and the intricate labor involved.
Historically, workers would have to cut through rock and earth, sometimes using explosives and tunnel-boring machines. They would then reinforce these tunnels with concrete or other sturdy materials, ensuring the structural integrity beneath existing infrastructure such as railroad tracks. The arduous labor of these workers and the sophisticated engineering strategies applied to overcome geographical challenges reflect the immense effort and ingenuity behind such undertakings.