With a loud "boom," the ground shook and rocks flew inside the diversion tunnel of the NEELUM-JHELUM Hydropower Station, which was under excavation. This was an extremely strong rockburst that occurred in Pakistan in May 2015. The tremendous destructive force severely damaged the tunnel boring machine, and the project was halted for repairs for seven months.
To solve this technical challenge, the supervising engineer selected one in a hundred and found Feng Xiating, director of the State Key Laboratory of Geomechanics and Geotechnical Engineering at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Using his team's proprietary technology, they equipped rockburst warning and prevention with a "stethoscope," enabling the project to be completed smoothly.
"Crying wolf" was people's past understanding of rockbursts. Feng Xiating's team used a self-developed high-precision warning system to catch this elusive "wolf."
Now, they have again set foot on the Qinghai-Tibet Plateau, serving the ongoing construction of the Sichuan-Tibet Railway.
A Battle That Made Them Famous
Rockburst is a geological hazard in which high-stress elastic energy accumulated in rock mass is violently released, causing rock to burst and eject. It is generally induced by construction and is common in deep underground engineering. Rockburst is also a worldwide challenge in the field of rock mechanics, with strong randomness, suddenness, and destructiveness, making it hard to guard against.
Feng Xiating told the China Science Daily reporter that he began rockburst research in South Africa as early as 1996. In the past, rockburst monitoring and protection were mainly based on qualitative analysis and empirical judgment, and the result was often "when you cry wolf, the wolf doesn't come; when you don't, it does."
In 2008, a project that took a key step toward solving this worldwide challenge emerged—the Jinping II Hydropower Station. As the on-site general manager, team member Chen Bingrui, a researcher at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, told the China Science Daily reporter that the rockburst monitoring and warning for the long diversion tunnel group of the Jinping II Hydropower Station was key for the team to move from the laboratory to field application.
The Jinping II Hydropower Station is one of the landmark projects of the "West-East Power Transmission" initiative. Its diversion tunnel group has an average length of 16.67 kilometers and a maximum burial depth of more than 2,500 meters, making it one of the most difficult hydraulic tunnels in the world to construct to date. Strong rockbursts occurred frequently during construction, causing serious harm to personnel and equipment.
Feng Xiating's team introduced microseismic monitoring technology into hydropower engineering. After nearly four years of unremitting efforts, they achieved the successful application of a complete set of key technologies, improved the stability and accuracy of microseismic source location analysis during the rockburst incubation process, and for the first time upgraded rockburst warning from qualitative to quantitative, supporting the smooth completion of the project.
An expert panel led by Qian Qihu, academician of the Chinese Academy of Engineering, evaluated the achievement as having "changed the traditional view held by some experts in rock mechanics academia and engineering circles that rockbursts cannot be monitored or warned against," and as having "provided an unprecedented example" for similar work in the geotechnical engineering industry in the future.
The initial success at Jinping brought this team into the international spotlight.
Accumulating Strength
After Jinping, Feng Xiating's team did not relax due to a lack of practical projects. Instead, they immersed themselves in strengthening basic research, publishing multiple influential academic papers in high-level international journals, while accelerating the development of equipment and breaking foreign technological monopolies.
"We spent several years summarizing our work results and conducting deeper analysis of the occurrence patterns and incubation mechanisms of rockbursts, with the aim of better applying them to engineering," Feng Xiating said.
Hard work paid off. It was this solid basic research that attracted the attention of consulting companies including experts from the American Hazar Supervision Company, who recommended the team to the contractor of the NEELUM-JHELUM Hydropower Station in Pakistan.
After years of theoretical accumulation, the team members who arrived in Pakistan were "raring to go." In the deep, hot tunnels of Pakistan, they used self-developed equipment and methods to set up a "net" for rockburst warning, and in a short time made on-site personnel go "from doubt to reliance."
Team member Feng Guangliang, an assistant researcher at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, who had long been stationed at the Pakistan project site, told the China Science Daily reporter that the team promptly and accurately warned of potential rockburst areas and levels during tunnel excavation, provided more targeted control measure recommendations, and provided scientific and technological support for the safety of construction personnel and equipment.
The participation of Feng Xiating's team effectively helped the tunnel break through ahead of schedule. Then-Pakistani Prime Minister Sharif, when attending the breakthrough ceremony, also praised the project for creating a miracle.
Because different projects and different geological conditions require different technical methods, rockburst warning requires long-term accumulation and systematic research. "Our innovation lies in studying the mechanism of the rockburst incubation process and finding the key to quantitative warning," Feng Xiating said. After engineering verification, the system's accuracy rate exceeds 80%, making it an effective method in practice.
At the same time, the recommended microseismic monitoring method proposed by Feng Xiating's team has been approved by the International Society for Rock Mechanics and Rock Engineering and has become an international standard.
At this time, new challenges have arrived.
Marching into Sichuan-Tibet
The Sichuan-Tibet Railway is called "the world's most difficult railway to build" and has carried the dreams of several generations. Surveying began in the early days of the founding of the People's Republic of China, but construction only truly began in 2014. In Feng Xiating's view, marching into Sichuan-Tibet is a responsibility for railway workers and also for researchers.
Team member Xiao Yaxun, an associate researcher at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, told the China Science Daily reporter that the Sichuan-Tibet Railway is located in a plate suture zone with ultra-high in-situ stress and a very high risk of rockbursts. It also faces many challenges such as high geothermal heat and difficult oxygen supply in tunnels.
According to reports, during the construction of the Lhasa-Nyingchi section of the Sichuan-Tibet Railway, a strong rockburst zone was encountered, with about 20 rockbursts occurring every day. One strong rockburst sent a 4-ton excavation trolley flying.
Feng Xiating recalled: "Difficulties and challenges such as high altitude and strong rockbursts did not make the team flinch. On the contrary, we volunteered to march into Sichuan-Tibet."
It is reported that in order to carry out 24-hour real-time monitoring, warning, and control, researchers have long been stationed in the tunnel construction area at an altitude of more than 3,400 meters. The temperature inside the tunnel is as high as 40 degrees Celsius and the humidity exceeds 90%, while the colorful steel plate housing where they stay is often freezing cold. "This instead inspired our fighting spirit," Feng Xiating said, adding that the role of rockburst warning in the construction of the Sichuan-Tibet Railway has gradually become apparent.
Regarding the Innovative Research Group of the National Natural Science Foundation of China that he leads, Feng Xiating admitted that the requirements are relatively high—members must be able to write high-level papers, solve practical engineering problems, and establish research directions in accordance with national needs and international frontiers. He said: "In the new era, building socialism with Chinese characteristics fundamentally relies on innovative development. According to the spirit of the 19th National Congress report, our research work should better serve the people's pursuit of a better life."
Today, China's large-scale projects such as highways, railways, and hydropower stations are advancing from east to west, gradually entering deep mountains; the "Belt and Road" construction is also advancing westward; and marching into the deep Earth to study internal problems and seek deep resources is also the general trend. Feng Xiating said: "Among these, rockburst is an unavoidable problem, and we feel a great responsibility."