The overall design of the underground city was finalized on April 5th.
The design of the overall structure was handled by the headquarters of the National Academy of Sciences in Jing City, while its branch campuses in Jiang City, Long City, Shan City, Hai City, and other locations were responsible for the design of crucial details.
It was ultimately decided that the underground city would adopt a modular construction approach with flexible connections.
Each underground city would be composed of countless modules. These modules would have diverse functions, including residential modules, ecological modules, and simulation modules for living; as well as farming modules, planting modules, and industrial modules for production; in addition to research modules, energy modules, and storage modules.
All modules of the underground city would reference the construction patterns of spacecraft.
Each module would have an independent life support system. Even if its entrances and exits were blocked, the people inside could still survive as long as they had sufficient food.
Because there was no need to be launched into space by rockets and no weight restrictions, the size of each underground city module was much larger than that of a spacecraft module.
Even a small residential module could accommodate 300 people, equivalent to a residential building.
As for large modules, they could simulate surface environments, with LED screens installed on the dome to perfectly replicate the sunrise and sunset of the sky before the apocalypse.
These large modules typically served as venues for schools, plazas, gymnasiums, and recreational facilities.
Fourteen days prior, when the design plan for the underground city was released, people felt much more at ease after seeing the conceptual diagrams of these underground city modules, believing that life underground could also be good.
In the design concept, the underground city was divided into four levels:
The first level, above 50 meters underground, including the surface, was the location of ordinary underground facilities that existed before the catastrophe. It was also the entrance and exit of the underground city, and could collect energy from the surface such as solar and wind power.
The second level, between 50 and 500 meters underground, was the main body of the underground city, housing underground agriculture, industry, medicine, underground ecological circles, and other modules, as well as residential areas.
The third level, between 500 and 2000 meters underground, was the underground energy circulation zone, for pumped-storage hydro, compressed air power generation, and underground thermal energy storage.
The fourth level, above 2000 meters underground, was for deep earth science laboratories and deep earth resource extraction.
What was currently being constructed primarily was only the section of the second level between 50 and 100 meters.
For the first level, the principle was to build as little as possible, directly utilizing the pre-existing structures from before the catastrophe.
As for the section of the second level between 100 and 500 meters, it would be excavated gradually after the first phase of the underground city was completed.
As for the third and fourth levels, they were currently only in the conceptual stage.
Once the underground city was built, all natural disasters on the surface, whether extreme cold, extreme heat, typhoons, blizzards, floods, or tsunamis, would have no impact on the underground city.
Only earthquakes would affect the underground city.
However, scientists had already devised a countermeasure by synthesizing a fluid to serve as the protective layer for the underground city.
This fluid was composed of a special viscous liquid and specially formulated powdery solids.
It had high density and strong viscosity, offering excellent shock absorption and thermal insulation properties. It was also resistant to high temperatures, corrosion, and abrasion, and it was conductive.
Wrapping it around the exterior of the underground city modules, or hollowing out the ground, injecting this fluid first, and then placing the underground city modules within it, could effectively protect the underground city from earthquakes.
In addition, the fluid's conductivity could assist in the application of wireless power transmission technology.
As long as the core energy module of the underground city remained intact, electricity could be transmitted to all modules through this fluid.
Because the fluid was conductive, it could also prevent underground creatures from intruding into the underground city.
Most importantly, when electrified, this conductor would generate a magnetic field. Under the guidance of another special device, it would firmly adhere to the modules of the underground city, preventing sinking or floating.
Even if the strata fractured, as long as the guiding was proper, and through the persistent efforts of the fluid, its shape would not be destroyed.
Even if soil and sand mistakenly entered it, they would be crushed and expelled by its strong cohesive properties.
Therefore, as long as the power supply was uninterrupted, the underground city would be perpetually protected by this fluid.
The design of the underground city did not arise out of thin air.
Before the catastrophe, people had already conceived of such an idea.
However, it was through the "Yugong Plan" that this concept was materialized, and it was also combined with the actual conditions of the current post-catastrophe era.
All technologies used in the design were at least at the pre-research stage.
The technologies used in the second level were all already developed and readily available, usable without further research time.
This was also why the overall design plan could be finalized so quickly.
After the overall design plan for the underground city was confirmed, following more than ten days of nationwide surveys, the first batch of underground cities was finally selected for construction in Long City, Jiang City, Shan City, and Hai City.
These four locations were all resource-rich, densely populated, and industrially comprehensive areas.
The national plan was to first concentrate the nation's strength to construct these first four underground cities.
After their completion, depending on the situation, a second batch of underground cities would be built.
Ultimately, the aim was to have underground cities spread across the country and connected by an underground transportation network.
However, Tang Li knew that not only would there be no second batch of underground cities, but even this first batch of underground cities would not be fully completed.
In the great tsunami of March of the following year, the Hai City underground city was destroyed when it was on the verge of completion and capping.
In the subsequent apocalypse, only three major underground cities remained.