Seismic engineering underground
Tashkent is in a zone of high seismic activity. The city was devastated by a magnitude 5.2 earthquake in 1966, an event that directly informed the metro's design when planning began two years later. Engineers designed the system to withstand a seismic event of up to 9.0 on the Richter scale. The tunnels, which vary in depth from 8 to 25 meters, feature a specialized construction to ensure their resilience.
The deep stations, such as Alisher Navoi and Mustaqillik Maydoni, and their connecting tunnels are particularly important. These were built using thick, reinforced concrete structures. An innovation was the use of flexible joints connecting the massive concrete or cast-iron rings that form the tunnel walls. This system allows the entire tunnel structure to deform by as much as 30 centimeters during an earthquake without fracturing. The deep stations were constructed within enormous excavated pits. After the station was built, the structure was surrounded by thick rubber padding before the pit was filled in, providing another layer of seismic isolation. This combination of deep, solid construction and planned flexibility makes the metro a robust piece of civil defense infrastructure, with heavy steel gates that can hermetically seal stations in an emergency.
Construction in challenging soil
The metro's builders faced significant hydrogeological challenges. The ground beneath Tashkent consists of unstable loess soil with a high water table, complicating any deep excavation. To overcome this, Soviet engineers employed an open-cut method for the stations. This involved excavating a large pit, constructing the station, and then covering it over. For the tunnels, more advanced techniques were required to stabilize the water-saturated ground and prevent collapse during boring.
The construction of the first line, the Chilonzor Line, began in 1972 and opened in 1977. Prominent architects and artists from across Uzbekistan participated in the design of the stations. The interior decorations use durable, locally-sourced materials like granite, marble, and ceramics. For instance, the columns in Mustaqillik Maydoni station are faced with marble from a quarry near Nurata, while walkways use highly durable granites designed to last for 150-200 years. Each station was given a unique artistic theme, from the mosque-like domes of Alisher Navoi to the cosmic murals of Kosmonavtlar, which shows Soviet space exploration.