How tunnels are built discreetly under Moscow city

By Raisa Ostapenko

MOSCOW, Jul 30 (PRIME) -- What would you say if I told you that, this very instant, a structure was being installed subterraneously right beneath your feet? According to Nikolay Agapov, the CEO of UniversalTonnelStroy, a Russian company that constructs tunnels, up to 500 meters of tunnels are built under Moscow daily.

Unbeknownst to most city dwellers, subterranean construction is not only frequent, but also goes entirely unnoticed due to modern minimally invasive technology that can build entire metropolises underground without compromising the soil and environment above.

Sometimes companies are faced with the challenge of building tunnels between structures that already exist underground, ones such as utility tunnels, cables, the city’s sewerage system, and Moscow’s celebrated metro.

More unusual encounters have also been noted. Agapov, for instance, said that his crew once uncovered a tunnel dating back to the reign of Ivan the Terrible, the Grand Prince of Moscow (1533-1547) and later Tsar of All Russia (1547-1584).

“The tunnel was egg-shaped and made of bricks,” said Agapov, who called the construction an impressive feat considering the absence of modern technology in the 16th century. Modern pipelines are made of concrete, steel, and polyethylene.

Last month, Transneft spokesman Igor Dyomin said that the oil transportation monopoly had completed renovating a 5.8 kilometer Soviet-era oil pipeline between Yaroslavl in central Russia and Moscow. The pipeline was built in 1978 and is the main route for the supply of crude to the Moscow Oil Refinery.

While segments of the pipeline are positioned aboveground, a good portion of it runs subterraneously under Losiniy Ostrov National Park in the northeast of Moscow and between the Novogireyevo and Novokosino stations of the yellow metro line.

Transneft decided that all construction and renovation would be made with the more expensive minimally invasive technique, which necessitated that the company seek the expertise of subterraneous tunnel construction contractors, including UniversalTonnelStroy.

“Subterraneous construction is more expensive than ordinary tunnel-building projects… the materials are more expensive, the technology is more expensive, people have higher salaries … All employees have very specialized higher educations … such projects necessitate government support, but are also a lot more cost-efficient in the long run,” said Agapov.

Agapov’s company used two types of tunnel-boring machines (TBMs) with thrust cylinders generating a force to push the machines forward: Earth Pressure Balance Machines (EPBs) and Slurry Shield Machines (SS).

The machinery, purchased from The Robbins Company, is controlled remotely through a computerized monitoring system, and is considered to be highly accurate, with an average margin of error of 3 millimeters.

EPBs are used in soft soil with no more than 700 kilopascals (7 bars) of pressure, themselves applying pressure to the soil around the cylinders to tamp it down and maintain a stable environment around the tunnel.

SSs use a “slurry wall” technique to reinforce tunnels built in soft ground having high hydraulic pressure. While a tunnel is dug, the surrounding soil is simultaneously mixed with a “slurry”, that is bentonite, an absorbent aluminum phyllosilicate which acts as a sealant and helps create a low permeability barrier which prevents water from flowing into the newly-dug trench and the walls of the trench from collapsing as a result of the great hydraulic pressure. The trench is gradually filled with concrete and the slurry is displaced, exiting the tunnel through a system of tubes.

The rate of TBM advancement has a direct correlation with the rate of soil removal, so as to prevent loosened soil from collapsing into the freshly-hallowed space.

The newly-replaced segments of the Yaroslavl-Moscow pipeline are expected to have a lifetime of around 100 years, as compared with the 60-year lifetime of its Soviet predecessor. The pipeline is well-protected both mechanically, as it is encased in a larger polyethylene tube, and electronically.

Preventing outside access and interference is extremely significant due to the high value of the product – oil – that is carried therein.

Construction of new segments of the pipeline and the renovation process was closely monitored by both a federal construction inspection committee and Transneft, with four inspectors always on-site to ensure that no violations were made.

UniversalTonnelStroy builds new tunnels alongside old tunnels, which are simply filled with sand or cement and left underground.

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