The construction of the Moscow metro is not only a technical feat, but also a real heroic story. For many years, the city was deprived of convenient transportation, and the construction of the subway was a necessity. However, the project was a real challenge for engineers and workers.
Before 1928, the geology of Moscow had been studied only to a depth of 15 meters, so any projects involving deeper layers were impossible. The soil was heterogeneous, there was a lot of underground water, and difficult areas made construction even more difficult. However, Stalin ordered the subway to be built to a depth of 65 meters.
By 1933, the plan was implemented only 0.5% due to numerous miscalculations and lack of workers. But by the end of 1934, the first branch of 13 stations was finished. And it was done by hand, with picks and shovels?
How did the subway manage to be built under such conditions? It is likely (given the discovery of huge networks of underground tunnels around the world) that such a drastic pace of underground construction may have contributed to the idea of using existing tunnels and passages that were discovered during the tunneling process.
Such an approach would have been the most effective, since it was easier to widen or repair, strengthen, and clad – already existing passages than to build new ones.