From pickaxe to diamond rotor: Building the Moscow Metro’s tunnels

The gigantic tunnel-boring machine, named Lily, weighs over 1,600 tonnes, is 66 metres long and has a diametre of over ten metres. The name sounds like a flower or a svelte woman, rather than a huge metal munching machine. This mechanised tunnel-boring machine, called a heading machine by builders, can replace two six-metre machines. In late 2016, Lily started a tunnel between the Kosino and Yugo-Vostochnaya stations on the metro’s new pink line.

Metro builders consider this a landmark event. The unique boring machine is larger and more sophisticated than its “sisters” and cuts double-track tunnels rather than the traditional single-track bore. A standard six-metre tunnel boring machine moves at about 250 metres per month, but Lily can move at up to 350-400 metres a month.

Powerful machines with “feminine” names

Tunnel-boring machines are given female names per a tradition conceived by Richard Lovat, the founder of the company LOVAT Inc. He decided that his company’s boring machines should receive female names in honour of Saint Barbara, the patron of underground workers. Alana, Almira, Anastasia, Natalia, Klavdia, Olga, Eva, Svetlana, Victoria, Polina and other “ladies” now perform the back-breaking male-oriented work in metro construction. 

The average distance between Moscow Metro stations is 2-2.5 kilometres. It takes a train three minutes to travel this distance. The tunnel-boring machine covers 12 metres daily. And 350 metres per month sounds like good news. Despite a complicated geological environment, some of the other “sisters” boast even more impressive results. For example, Tatiana linked the Ochakovo and Michurinsky Prospekt stations with a 2.8-kilometre right track running line’s tunnel several months faster than planned.

Electronic navigation and relaxation room inside the metal “worm”

The boring machine, or shield’s sections are delivered to the construction site and assembled there in a special pit called the assembly chamber. The site measures 60 by 70 metres and is almost as large as a football field. This is where the tunnel begins. The machine will complete the tunnel in a dismantling chamber, where it will be disassembled and later used for other projects.

Shaped like a giant worm, the “shield” measures up to 100 metres long. Its forward-based cutting mechanism is called the rotor. The cutters gnaw their way through the earth. The cutting mechanism’s servo-drive is located behind the rotor.

The machine has a closed cement-solution tank for filling cavities between tubbing sections and the earth, a pressure chamber, an operator’s cabin and even a relaxation room for a crew working 24 hours a day. About 30 people operate and maintain the heading machine in three shifts a day.

The machine finds its bearings with a high-precision electronic navigation system. An operator constantly checks the route coordinates because the machine cannot deviate by more than eight mm from the preset path. The machines are carefully scheduled to make the most efficient use of their time.

Concrete tubbing sections form the tunnel. After the tunnel has been completed, builders lay tracks and install utility lines. The earth is removed from the machine’s holding crates via mine cars that reach the surface on temporary tracks. Mine cars also deliver essential components, including the concrete tubbing. The earth is taken to special waste disposal facilities. Up to 30 lorries will move the earth from one heading machine each day.

Unconventional approach: extended heading machine and escalator tunnel

Construction crews have to improvise in some cases due to a shortage of construction sites. The heading machine used to build the Delovoi Tsentr station on the yellow line was assembled on an area the size of a school gym. Workers extended the machine by lowering rings or tubes underground, one after another.

Workers raced against time, while assembling the machine at Petrovsky Park station. It usually takes 30-60 days to put it together. This time, the machine’s entire forward section, weighing about 150 tonnes, was not dismantled but lowered intact 28 metres beneath the ground. A 450-500-tonne crane was installed on the pit’s rim for this purpose. Engineers conducted several calculations to see that the crane would not cause the pit to collapse.

Moscow’s contractors were creative when using a heading machine to bore escalator tunnels at an angle for the Maryina Roshcha station on the light green line for the first time in history. This approach has not caught on elsewhere because European countries mostly build shallow level metro stations, and escalator tunnels are dug manually there.

The secret of double-track tunnels

Lily, the giant boring machine, builds double-track tunnels. A standard station features an island platform with tracks on both sides. The new stations with double-track tunnels will have rails running in both directions in the hall’s centre with two platforms on each side of the tracks. That’s why such tunnels are referred to as double-track ones.

Ten-metre tunnels take more planning and effort to build than their six-metre (diametre) equivalents. Why do they build double-track tunnels? First, a single tunnel is faster to build than two tunnels. Second, it cuts costs by about 30 percent.

 

The city is to build over 20 kilometres of double-track tunnels in the next three years. The metrio’s Kozhukhovskaya Line will receive two such tunnels, and two more are scheduled to be built on the Third Interchange Circuit in northern and eastern Moscow. This method is referred to as Spanish technology and is used all over the world, including Madrid where double-track tunnels account for 90 percent of all metro tunnels.

How the naval ship-worm helped invent the tunnel-boring machine

As legend has it, British engineer Sir Marc Isambard Brunel invented the tunnel-boring machine after studying the movement of naval ship-worms. The worm’s head is covered with a rigid shell for boring through wood and covering the tunnel with a layer of lime.

Russian Emperor Alexander I asked the inventor to design a tunnel under the Neva River in St Petersburg and to build it using his new machine, but these plans were never implemented. The Emperor later ordered construction of a bridge in the vicinity, and the machine built the world’s first tunnel in London, rather than St Petersburg.

Moscow sets records

The city’s first metro builders had only eight horses and one lorry, and they had to borrow spades and shovels from the street cleaners. The first tunnel-boring machine was used here in 1933-1934 for building a section between Lubyanka and Teatralnaya squares. It became easier and safer to build deep tunnels using these machines. US engineer George Morgan, who provided consulting services to Moscow builders, warned that the heading machine could only travel 75 centimetres a day. But Moscow’s engineers managed to increase its speed and dig a record-breaking 4.5 metres in 24 hours.

Modern tunnel-boring machines, including the latest heading machines from Germany’s Herrenknecht, Canada’s LOVAT and Robbins of the United States, are dozens of times faster. It took Herrenknecht almost 12 months to develop Lily, which was delivered to Moscow in April 2016. Anastasia and Almira also arrived here from Germany.