Shan Jixiang, Director of the former imperial palace, said people usually think the walls are much more solid, but detailed investigation shows a different reality.
Experts recently completed a survey of the condition of more than 3,400 meters of wall, which showed that some parts have been hollowed out over time, and are sinking. Grass and tree roots have infiltrated gaps.
A 230-meter section of the western walls, which are the most damaged, has been chosen for refurbishing first.
The Forbidden City was built in 1420. Its surrounding walls are 9.3m high and 8.5m thick. Their core is made of earth and the outer part is made of bricks.
Many wall sections underwent repairs in the 17th and 18th centuries, after torrential rains and earthquakes. In 1988, the northern section broke down. In 1999 and 2000, the palace was restored, mainly on the surface.
This time, experts will conduct in-depth restoration using high-tech equipment like earth-penetrating radar.
Engineer Zhao Peng said his project team will apply China’s traditional building methods combined with hi-tech equipment.
He pointed out difficulties, saying using new brick is easier than reusing the wall’s materials. But it’s important to use the old bricks as much as possible when repairing cultural relic sites, he said. It’s a challenging task combining both new and old materials.
The restoration project will be completed by October, 2020, when the Forbidden City will be 600 years old.