What is the metaphor of a natural barrier changing into a thoroughfare?

The natural barrier becomes a thoroughfare, which means that after the completion of Wuhan Yangtze River Bridge, the natural barrier of the Yangtze River becomes a smooth road.

This sentence comes from "Water Turning Around", and the whole word is: only drink Changsha water and eat Wuchang fish. Across the Yangtze River, you can see the endless sky. No matter how stormy it is, it's better to walk around leisurely. You should have a rest today. Zi Zaichuan said: The deceased is like a husband! As soon as the wind blows, the tortoise and snake calm down, and the grand plan has been set. A bridge flies north and south, and the natural barrier becomes a thoroughfare. The stone wall of Xijiang River is stronger, and the high gorge comes out of Pinghu. The goddess should be safe and sound, and will surprise the world.

The meaning of the poem is that as soon as Confucius finished drinking the water in Changsha, he sighed on the shore: Time is like running water! The sails are floating on the river, the tortoise and snake mountain stand quietly, and the grand plan rises in the chest. The bridge will fly across the north and south, and the natural moat of the Yangtze River will be unimpeded. I will also erect a dam on the west side of the Yangtze River to cut off the rainy floods in Wushan and make a flat reservoir appear in the Three Gorges. The goddess must be very healthy, but she will marvel that the world has changed. ?

Construction history of Yangtze River Bridge

Nanjing is located in the lower reaches of the Yangtze River, where the river is wide and the water is urgent, and the engineering geological conditions are complex. As early as 1927, Walter, a bridge expert, came to Nanjing for a field trip and left a sentence: "It is impossible to build a bridge in Nanjing." In addition to the obstacles of geographical environment and geological conditions, in 1960, the bridge project encountered economic difficulties as soon as it was launched, and the construction of the bridge seemed to be an "impossible task". ?

On September 1964, 18, when the caisson of No.5 pier of Nanjing Yangtze River Bridge reached14.2m, many anchor cables of the caisson guide group were washed off by the flood peak rapids in autumn flood season, and the huge floating body kept swinging in the river, which was extremely dangerous.

After suffering, at the end of 1968, the railway bridge and highway bridge of Nanjing Yangtze River Bridge were successively completed and opened to traffic. The city of Nanjing is crowded with people, and even the trees and walls are crowded with people watching this "race bridge".