New tech preserves Yungang Grottoes

Visitors are awestruck the moment they see the giant Buddha statues and exquisite carvings at the Yungang Grottoes in Datong, Shanxi province. A UNESCO World Heritage site, the grottoes comprise 45 major caves and more than 59,000 statues — an outstanding achievement of fifth — and sixth-century Buddhist cave artists in China.

Yet behind this magnificent legacy lies an insidious threat: rock weathering, driven largely by water.

Although practitioners in the cultural heritage field can monitor and treat condensation on rock surfaces, they lack effective means to detect concealed condensation inside rocks in real time.

A monitoring and intelligent regulation system for condensation inside rocks has now been put into operation at the Yungang Grottoes, marking a key technological breakthrough in protecting China's cave temples.

The system was unveiled at the International Forum on Cave Temple Conservation 2026, which was held in late September in Datong.

The forum aims to build global consensus on cave temple conservation, share frontier technologies and successful experiences, address common technical bottlenecks, and promote a long-term mechanism for international cooperation in the field.

Under the theme "Conservation of Cave Temples Under Global Climate Change", the forum brought together more than 30 scholars and experts from home and abroad, including those from the United States, Italy, Cambodia, and Nigeria.

They shared cutting-edge practices and theoretical findings in three thematic sessions: cave temple conservation and technological innovation under climate change, archaeological research and value interpretation of cave temples, and cave temple conservation and international exchange.

Zhu Xiaodong, vice-governor of Shanxi province and Party secretary of Datong, said in his speech that in recent years, water seepage and unstable rock formations at the Yungang Grottoes have been effectively treated, and conservation efforts are shifting from emergency rescue to preventive and research-based approaches.

Huang Jizhong, dean of the School of Cultural Heritage and Information Management at Shanghai University, delivered a speech on key technologies for preventing water damage within the stone relics of the Yungang Grottoes.

"The greatest difficulty in controlling condensation is predicting where and when it is likely to form. Based on our laboratory research and simulation models, we are able to determine how condensate water forms," Huang said.

According to him, using AI-powered nondestructive detection technologies, the research team can quantitatively identify sandstone's pore structure and mineral composition without sampling or drilling, and identify the depth at which condensation forms inside rocks.

Huang and his team demonstrated through experimental research that, under certain conditions, condensation first forms inside the rock before any moisture appears on the face of the stone.

"The depth of condensate water differs across sandstone of various weathering levels. The more severely weathered the rock, the deeper water lies within the stone," he said.

Backed by Shanxi provincial authorities, the ambitious project — jointly undertaken by Shanghai University, the Yungang Research Institute and other institutions over three years — systematically tackled the challenge of condensation inside rocks.

At Caves 9 and 10 of the Yungang Grottoes, the research team has built a comprehensive monitoring network covering areas from outside the cave entrance to deep within the rock mass.

Dozens of sensors stream real-time micro-environmental data, including temperature, humidity and wind speed, feeding the prediction models that deliver early warnings of hidden condensation within the rock.

Once an early warning is issued, an intelligent regulation system combining natural ventilation, forced ventilation, dehumidification, and graphene-based temperature control starts operating. These devices run at different levels depending on the incident. Data indicates the system has an effectiveness rate of more than 97 percent in suppressing condensation formation.

"Ultimately, we have realized the goal of making condensation seen clearly, measured accurately and treated effectively," Huang said.