Projects for constructing a tunnel under the Amur River arose in connection with the construction of the Trans-Siberian Railway. In 1913, at the Priamurye Regional Exhibition, a drawing of such a tunnel was presented, but by that time the choice had already been made in favor of a bridge.

Plans for constructing a railway tunnel under the Amur appeared as early as the beginning of the 20th century. In 1906, surveyors of the future Amur section (Kuenga-Khabarovsk) of the Trans-Siberian Railway arrived at the banks of the great Far Eastern river. Based on the conducted work, several projects for a bridge and an underwater tunnel were proposed. Incidentally, visitors to the Priamurye Regional Trade and Industrial Exhibition, dedicated to the 300th anniversary of the Romanov dynasty and held in 1913 in the regional capital, Khabarovsk, could see a projection drawing of the tunnel depicting a train making its underwater journey. However, at that time, the bridge crossing project over the Amur “won.”

Moreover, the events of the Civil War showed how vulnerable the narrow rail link of the Amur Bridge was. On April 5, 1920, two bridge spans were blown up by retreating partisan units to block the way to the left bank of the river for Japanese interventionists. This caused a break in the Trans-Siberian Railway for a full five years, cutting off the Far East from Russia and Siberia, and railway traffic was rerouted via Manchuria along the Chinese Eastern Railway (KVZhD).

In the 1930s, second tracks were being constructed on the eastern sections of the Trans-Siberian Railway. The need to build a tunnel was due to Japan’s occupation of Manchuria in 1931, the loss of the KVZhD, and, accordingly, the vulnerability of the bridge. In 1936, considering the special strategic importance of the Trans-Siberian Railway for the country, the General Staff of the Red Army initiated a decision to build the tunnel.

For conducting engineering and geological surveys of the future tunnel, a special expedition from Soyuztransproekt was sent to Khabarovsk, including specialists from Metrostroy, then part of the People’s Commissariat of Railways (NKPS), and the Kuibyshev Military Engineering Academy. On the territory where construction was planned, a whole network of securely fixed geodetic points—metal marks embedded in massive concrete monoliths—was established. The coordinates of these points were determined by three independent teams of surveyors and consolidated for control under one authority. In case of unacceptable deviations by any team, the work was repeated by all three. Subsequently, the obtained data were used by underground surveyors—mine surveyors—who, having studied the conditions set by the designers, worked on the surface referencing these marks, and then laid out the tunnel axes deep underground. As an object of state importance, the tunnel was strictly classified and assigned the number 4 NKPS. It is no surprise that until recently little was known about this construction.

The survey work was carried out at a rapid pace—only five months from September 1936 to February 1937. When approving the route of the tunnel crossing under the Amur River, nine options were considered. The design was carried out by the Metrostroy Institute under the leadership of Academician Vedeneev. The chosen option met air defense requirements: the object was located 500 meters away from the bridge. On March 22, 1938, by decree of the USSR Council of People’s Commissars and the Central Committee of the All-Union Communist Party (Bolsheviks), the project of the Amur tunnel, 7,120 meters long, with a 3,600-meter underwater section and a depth of 10–14 meters, was approved.

According to the government decree of June 7, 1937, work began on the object “Construction No. 4.” Following the established practice of socialist construction, work started “without waiting for the development of the technical project and general estimate.” The latter part of these basic documents was received by the builders only in May 1939. The general estimate for the project was approved in August 1940. The cost of the tunnel crossing was set at 294.5 million rubles. The deadline for completing all construction work and commissioning the tunnel was December 1939.

Tunneling began at the end of 1937 and was carried out by fifteen separate construction enterprises with the participation of military engineering units. The construction was overseen by the People’s Commissar of Railways of the USSR, Kaganovich. After several replacements, the chief and main engineer of the construction management was appointed as the experienced civil engineer Ermolaev, who led the construction until its full completion. Surface work (quarrying crushed stone, building houses, and other above-ground structures of the crossing) was carried out by railway troops. The work directly on the tunnel under the Amur was performed by 900 specialists in key professions seconded from Metrostroy and 1,000 local hired civilians. The total number of workers engaged in construction varied, averaging 5,500 people per year. Prisoners worked in the Tungus and Novokamenny quarries, where limestone for the construction was mined. Railway troops handled crushed stone preparation, house construction, and other above-ground structures of the crossing. Cast iron tunnel rings were supplied by the Magnitogorsk plant.

To increase the work front along the construction route, four shaft wells were sunk, through which non-mechanized shields were lowered and installed down to the design level. At each tunneling shield, a specific point became the object of daily close attention by three independent mine surveying teams. They laid out the tunnel axis along these points, figuratively speaking, like sailors navigating a ship’s course in fog, but with incomparable precision.

The tunneling was very difficult because the tunnel was laid not in a straight line from bank to bank but along a complex curve, both in plan and vertically. At the same time, the highest accuracy was required. The axis misalignment allowed at the tunnel breakthrough was no more than 5 centimeters. At the breakthrough of the Amur tunnel, the axis misalignment was only 15 millimeters. Despite local significant water inflows in the adit, an unprecedented speed for that time in the world was achieved for tunneling with non-mechanized shields in rock formations—about 5 meters per day. During construction, 1,475,000 cubic meters of soil were excavated, and 137,600 cubic meters of concrete were pumped.

The 7 km path was completed using five shields over 3,627 meters, as well as by mining methods (from three faces) on the eastern section, and by open-cut method on the western section 1,350 meters long. The internal diameter of the tunnel is 7,400 mm in the underwater part.

The tunnel breakthrough occurred in June 1941. By peacetime standards, at least another six months were needed to fully complete the work. But soon a telegram from the State Defense Committee, signed by Stalin, arrived at the construction site with an order to complete the work quickly and open the tunnel for train traffic. Within the allotted time, all scaffolding and temporary access roads were dismantled, 8,000 cubic meters of crushed stone ballast were laid, and the main track was installed. On the appointed date, July 20, 1941, the first train with construction participants passed through the completed tunnel, driven by engineer Vasily Vozheyko. On April 25, 1942, a government commission accepted the tunnel for permanent operation with a rating of “good,” and the work of the mine surveyors received an “excellent” rating. To ensure normal operation, the tunnel was equipped with ventilation, heating, lighting, water pumping, warning, and blocking signaling systems. For its time, it was capable of withstanding the most advanced military technologies. Thanks to this margin of strength, the tunnel still retains all its operational parameters today. In 1944–1945, cargo transportation related to the upcoming military operations against Japan began. According to the order of the People’s Commissar of Railways Kovalyov dated May 22, 1945, accelerated work was carried out on the Far Eastern Railway to adapt the tunnel crossing under the Amur for the passage of all types of transport and military units.

During the Great Patriotic War, approaches to the Amur bridge and tunnel were guarded, including by anti-aircraft batteries. One of them, located on the shore of the Beshenaya Channel, fired a shot during all years of combat duty. A soldier of this battery, Lelikov, later recalled how one day the Air Warning Post reported an unidentified aircraft approaching the bridge. The command “Alert. Load live rounds” was given. Soon the aircraft was spotted and guided by the battery observers. However, before reaching the firing line of our battery, the aircraft turned away and flew toward Manchukuo. Since anti-aircraft guns are unloaded only by firing, the shot was soon made.

After the end of hostilities in the Far East, the tunnel remained in conservation as a secret object until 1964. From the mid-1960s, to increase the capacity of the Amur bridge, the single-track tunnel began to be used for freight trains moving westward (odd direction). From the early 1980s, after the electrification of the Far Eastern Railway from Khabarovsk to Bira, passenger trains, including suburban ones, also began to pass through the tunnel. Due to growing freight traffic and to increase the capacity of the Trans-Siberian Railway, in 1964 the tunnel was used for freight trains in the odd direction (east to west). After the railway electrification was completed, passenger trains also started running through the tunnel.

At the time of construction, the Amur tunnel was the longest in the world by the length of its underwater section and the longest tunnel in the Soviet Union.

As of 2008, trains run both above the Amur—over the railway bridge—and through the tunnel. After the completion in 2009 of the second phase of reconstruction of the Amur bridge, the opening of two-way traffic on it resolved the “bottleneck” problem of the Trans-Siberian Railway. This made it possible to carry out the reconstruction of the underwater tunnel, after which the crossing of the Amur by the Trans-Siberian Railway is carried out on three tracks—two on the bridge and one through the tunnel. Currently, a project for the tunnel’s reconstruction is being developed.

Near the eastern portal of the tunnel, a granite plaque is installed with the words: “Glory to the warriors of the 7th separate Order of the Red Banner of Labor railway brigade, who built the tunnel under the Amur River bed 1938–1941.”

Sources:

https://ru.wikipedia.org/wiki/Тоннель_под_Амуром

https://amurmedia.ru/story/tonnelpodamurom/index.html

https://dzen.ru/a/YqMzWlG6sy0PKXyp