By Elina Lee

The Grand Sanyang Road Tunnel

By Elina Lee

W uhan,the capital city of Hubei Province,is rich in grand rivers,beautiful bridges as well as impressive tunnels.The first Yangtze River bridge and the first Yangtze River tunnel originated in this city. Besides being beautiful scenery for visitors,bridges and tunnels here have held many records both at home and around the world.The construction of the Sanyang Road Tunnel across the Yangtze River is a new breakthrough in the world history of tunnel construction.

The firstrail-and-road shield tunnel in the world

The Sanyang Road Tunnel is the first rail-and-road shield tunnel in the world as well as the first massive-diameter cross river tunnel in the upper middle stream of the Yangtze River.With two extra-large shield-tunneling machines,each weighing 3000 kilograms, tailor-made and imported from Germany,the outer diameter of the tunnel will reach a colossal 15.2 meters after its completion,the third largest in the world,and making its cross-sectional area 3.5 times that of the Channel Tunnel.

Cross-sectional view of the Sanyang Road Tunnel

Model of the Sanyang Road Tunnel

The Sanyang Road Tunnel will divide into three layers:The top layer will be for ventilation;the 3-driveway-wide middle layer for buses and cars;and the bottom layer will run metros for Wuhan’s Number 7 Subway line together with safety evacuation for passengers.Compared to the well-known Channel Tunnel which was opened for the transportation of trains 22 years ago,the Sanyang Road Tunnel will allow buses,cars, and metro trains to run through it simultaneously.

By the time of its completion,the tunnel will require the disposal of 2.7 million cubic meters of earth; this huge amount is enough to build another 420.5-meter-high Jinmao Tower.In other words,if the soil excavated from under the Yangtze River were to be converted into football yards,there would be 25 standard football yards and each would contain soil 10 meters high.

Experiencing and resolving problems

When embarking on such a huge project,the engineers and construction workers have to deal with immense difficulties including high water pressure and complex geological structures.

The Sanyang Road Tunnel undergoes the highest water pressure in China and the maximum water pressure it can sustain is 0.63Mpa,which feels like the area of one’s fingernail bearing a weight of 6.3 kilograms.Experts have applied the“segment joint waterproofing”technology to help the tunnel survive this pressure.

You may be wondering,when it rains,will any leakage occur?The answer is simply no.Due to the sophisticated design inside the tunnel,at every entrance,a water pump room is set up in order to discharge rainwater,cleaning water and fire-fighting water;this enables the tunnel to discharge a maximum of 1580 cubic meters of water per hour.

The geological conditions under the Yangtze River bring another challenge to the tunnel construction. In the toughest sections,the shield-tunneling machines may have to go through complex layers of mud in the upper layer and rocks as hard as steel in the lower part, which may make it difficult to push through and can easily cause damage to machinery.However,by applying the latest high-tech machinery to the project this problem turned out to be no big deal.The two machines,though with a cutter head diameter of nearly 16 meters,are not clumsy as one may expect.Under normal pressure underwater,they can switch cutters according to specific geological conditions,allowing them to cope with geological challenges even while encountering mud and rock in the same cross section.

A safe and sound way oftraffic

After persevering through all of the complex technological difficulties, the Sanyang Road Tunnel endeavors to bring citizens in Wuhan a more convenient route through the city in a safe and sound way.

Cross-sectional view of Xujiapeng Station on Qinyuan Road,the starting point of the Sanyang Road Tunnel in Wuchang District

Upon its completion,the total length of the Sanyang Road Tunnel will reach 4650 meters,linking Qinyuan Road in Wuchang District to Sanyang Road in Hankou District across the Yangtze River.The tunnel will help enhance the traffic link between the central Hankou region and the riverbank area of Wuchang,essentially reducing the transportation congestion,which currently occurs on the Second Wuhan Yangtze River Bridge and Qingdao Road Yangtze River Bridge.

As estimated by a popular map app,at present it takes 22 minutes to drive from Qinyuan Road in Wuchang to Sanyang Road in Hankou,and 45 minutes by bus. However,upon completion of the tunnel it will just take a mere 5 minutes for a car to go through at a speed of 60 kilometers per hour, and 2.5 minutes for a metro train to complete the journey at a speed of 80 kilometers per hour.

In order to ensure ultimate safety standards for the traffic,Shanghai Tunnel Co.Ltd,the construction company of the project,have also taken into consideration many other precautions such as fire prevention and anti-explosion.

Working Shaft of the Sanyang Road Tunnel(Wuchang Section)

On the top of the tunnel, dedicated exhaust channels are set up for ventilation,these allow a maximum of 3600 cubic meters of gas to be exhausted per second.The inside structure of the tunnel is made of fireproof boarding,capable of tolerating temperatures up to 1200 degrees for up to 2 hours.It is also equipped with automatic fire and smoke detection alarms.

To further guarantee the safety of the traffic and passengers in the tunnel,the construction workers have also applied an anti-explosion system together with specialized evacuation exits,lighting and ventilation systems in addition to high definition traffic cameras, which are installed every 75 meters in the tunnel.

The Sanyang Road Tunnel is a great milestone of infrastructure construction history,and will effectively display how the advancement of technology truly benefits people’s lives.