Nanjing Metro staged a rare crossing battle
Guide: Nanjing Metro Line 1, which meanders from south to north, encountered Jinchuan River, Ming city wall and Xuanwu Lake after leaving Xuanwu Gate. It is not only necessary to cross the river with dense pipes, but also to pass through the road tunnel that has just been completed and opened to traffic, but also to ensure the absolute safety of national treasure level cultural relics
Nanjing Metro Line 1, which winds from the south to the north, came out of the Xuanwu Gate and "encountered" Jinchuan River, Ming city wall and Xuanwu Lake. How did Nanjing Metro win this rare crossing war when it was necessary to cross the rivers with dense pipes, pass through the road tunnels that had just been completed and opened to traffic, and ensure the absolute safety of "national treasure" cultural relics
the world's top shield machine plays the "leading role"
with the opening of the whole line of Nanjing Metro Line 1, the crossing war has also been settled. On February 10, he came to the construction site and visited the builders who created many miracles in the history of subway construction. Lirongzhi, manager of the third TBM company of China Railway Tunnel Group, who was responsible for the construction here, told us that they had won this difficult battle for more than two years with the world's top shield machine
manager Li said that the shield machine is the most advanced equipment in metro construction at present, and the earth pressure balance shield machine imported from Germany is also a cutting-edge product among shield machines. The "big guy" has an outer diameter of 6.4 meters, a two-story building, a length of 64 meters and a weight of more than 400 tons. There is a special "man cabin" on the shield machine for the construction personnel to operate in. In case of special circumstances, they can also enter the front cutter head for troubleshooting. The shield machine wielding a huge cutter head with a diameter of 6.4 meters sneaked under the ground like an earthworm, creating the highest domestic speed of driving 432 meters per month. What is more unique is that the shield machine is also equipped with advanced geological drilling and prediction devices, just like the "scout", which can "probe" the geological conditions ahead at any time during the propulsion process, so that the construction can be adjusted accordingly in time
and Xuanwu Lake highway tunnel "
as two major construction projects in Nanjing, it is more important for Xuanwu Lake metro tunnel and highway to lay a good foundation for the" new hardware era ". The road tunnel" meets "here, and the two intersect stereoscopically at the T-junction of new model road and central road. The overall development level of China's new material industry still lags far behind that of developed countries. Manager Li said that the minimum net distance between the subway tunnel and the highway tunnel just opened to traffic is only less than 1.2 meters. Such a "close distance" is unique in domestic subway construction. In addition, the impact of highway tunnel on metro tunnel is nearly 28 meters long, which makes the construction more difficult
in order to ensure that the shield machine will not cause large settlement or uplift when passing through the highway tunnel, the shield machine starts to control the tunneling posture, adjust the tunneling parameters, slow down the "pace" and sneak "gently". The bottom line of the government's environmental supervision is the same. 1. When it falls behind again, foam agent and bentonite are added in front of the cutter head to improve the performance of the residue and prevent "sand gushing" and "water gushing". In addition, a number of earth pressure boxes of shield machines are buried for 24-hour monitoring to escort the excavation
"national treasure" the Ming city wall was undamaged
the Ming city wall, a national first-class cultural relic, is the pride of the ancient capital Nanjing, but no one thought that one day she would work out "test questions" for the subway construction. The foundation of the Ming city wall is wooden row piles, which requires high construction settlement. At the same time, the local load caused by the gravity of the city wall increases, which have become urgent problems to be solved in the subway tunnel construction. How can we achieve the best of both worlds when the ancient civilization and the modern civilization intersect
manager Li said that in view of the situation, they calculated the soil pressure at the tunnel excavation section by section during the construction, and acted the Ming city wall as a strip load on the ground. The shield machine gradually increased the soil pressure within the influence range of the city wall, and gradually reduced the influence range of "walking" the city wall, so as to avoid the ground settlement caused by the unbalanced thrust of the shield machine to the greatest extent. At the same time, pay close attention to the composition of the muck. When wood chips are found and it is difficult to dig, the constructors enter the "human cabin" to eliminate the danger... Finally, the news that the monitoring data shows that the ancient city wall is safe and sound came, which makes the builders proud