On August 16, the 2nd Summer Youth Olympic Games opened in Nanjing. A month ago, the twin towers of the Nanjing Youth Olympic Center, constructed by China Construction Third Engineering Bureau East China Company, had already lit up their landscape lights. The twin towers are like two swords piercing the sky, and like two pillars holding up the heavens. It is this building that set the world's first record for the "full reverse construction method" in a 300-meter super high-rise building.

On April 26, 2012, construction of the Youth Olympic twin towers officially began. The project has 3 underground floors, with Tower A having 58 above-ground floors and a height of 255 meters, Tower B having 68 above-ground floors and a height of 314.5 meters, and a 5-story podium. The total construction area is 287,000 square meters. As a landmark building on the Youth Olympic axis, whether the twin towers of the Nanjing Youth Olympic Center could close their exterior curtain walls before the opening of the Youth Olympic Games and form a beautiful appearance was crucial to Nanjing's city image.

From the start of the project to the opening of the Youth Olympic Games, there were only less than 2 years and 4 months. Considering the preparatory work before the opening ceremony, the exterior curtain walls of the Youth Olympic twin towers had to be closed another month earlier. If conventional construction methods were used, it would take at least 3-4 years to complete pile foundation construction, foundation pit support, earthwork excavation, underground structures, above-ground structures, and curtain wall engineering, which meant the Youth Olympic twin towers could not be completed before the opening.

　　First excavate the foundation pit, then build the building layer by layer upward—this is the high-rise construction method in most people's eyes. The reverse construction method breaks traditional concepts by using the floor slabs, beams, plates, columns, and exterior wall structures of the basement as the support structure for construction. While constructing the basement structure from top to bottom, the above-ground structure is also constructed, effectively adding a work surface.

"Generally, buildings have the main tower constructed conventionally and the podium constructed in reverse, but the main towers and podium (sharing one basement) of the Nanjing Youth Olympic Center twin towers are 'fully reverse constructed,' which is unprecedented in global construction history," said project manager Zhu Huiqing. The project first constructs the pile foundation and diaphragm wall as the foundation of the entire tower. The maximum pile diameter reaches 3 meters, and the deepest extends more than 90 meters underground, equivalent to digging a 30-plus-story high-rise underground. More than half of the engineering piles also have steel columns inserted with a vertical precision requirement of 1/500; the diaphragm wall, as the enclosure structure of the entire basement, reaches a maximum depth of more than 60 meters.

　　"Next, earthwork excavation for the first basement level is carried out," Zhu Huiqing introduced. Unlike conventional practice, the earthwork excavation does not directly dig to the bottom of the twin towers. Instead, after the earthwork of the first basement level is removed, the roof slab and floor slab of the first basement level are poured, with corresponding earth removal openings reserved for transporting earthwork from the next level. "This is actually like using the first basement level as a temporary 'bottom' for the high-rise, utilizing the 'bottom' structure and the pile foundation diaphragm wall to work together to achieve simultaneous upward and downward construction, followed immediately by construction of the second and third basement levels."

　　On April 30, 2013, when the large bottom slab of the third basement level was sealed, the upper tower structure had already been constructed to the 17th floor. At this point, the "full reverse construction method" for the Nanjing Youth Olympic Center twin towers and podium was declared complete, one year ahead of conventional super high-rise construction methods. Experts say that the application of this process not only shortened the construction period by one-third but also resulted in small deformation of the building foundation pit and little impact on adjacent buildings. At the same time, it saves the support costs of the retaining structure and has significant economic benefits. (Source: People's Daily)