National treasure pagoda in Nara has delicate surgery
The Asahi Shimbun by YUMI KURITA/ Staff Writer November 3, 2016
The podium beneath its Toto (east pagoda), a government-designated national treasure, is being strengthened by covering it with steel-encased reinforced concrete (SRC).
The 34-meter-tall structure, built around 730 in the Nara Period (710-784), has been dismantled for an overhaul for the first time in about a century.
It's hoped the advanced technology will help avoid damaging the invaluable remains of the podium.
Yakushiji’s Toto, a wooden three-story pagoda, is believed to be the sole surviving edifice from the original temple. It showcases the style of the Hakuho culture, which prospered from the second half of the seventh century through the early eighth century.
Each tier of the pagoda has a smaller, second roof. The rhythmical, stylistic beauty of the double-roof structures has earned it the eulogy “frozen music.”
A podium dating back to the original temple, measuring about 13 meters per side, has been unearthed during the dismantlement and repair work, which began in September 2011.
It was found to contain vestiges of careful engineering work, including the use of the “hanchiku” consolidation method that hardens layers of earth, as evidenced by the presence of about 25 layers of packed-down earth.
A drilling survey also found that the podium's earth had absorbed too much groundwater to retain its initial strength. Many cracks were spotted and the foundation stones were also found to have sunk up to 24 centimeters.
An expert panel believes the weakened podium cannot fully support the 400-ton pagoda body.
To strengthen the podium, work began in August work on a new concrete “podium” that is being built atop the original one. The same technology used to build a high-rise building on a cramped plot of land was applied. Twenty-four piles were driven to a depth of 12 to 13 meters, eight of them at locations where excavation studies had been finished and the other 16 outside the podium.
The workers are planning to place an SRC beam system shaped like a “kotatsu” heater table frame on top of the piles, and to place a 15-cm-thick concrete plate on top of the beam system so the plate will serve as a new podium in the future.
Pillars will be erected on base stones to be installed on top of the new podium. The work is expected to be completed in the early summer of 2020, by which time the pagoda will be standing about 1 meter higher than before.
“We have racked our brains so as not to do harm to the remains, and have come up with this method for preserving the original podium,” said Kakichi Suzuki, a former director of the then Nara National Cultural Properties Research Institute who heads the expert panel. “It is an achievement of sorts as a way to use contemporary technology to conserve a cultural property.”