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[Everest Scientific Research] Search for traces at the disaster site to crack the mystery of long-distance high-speed landslide

Editor’s Note: In order to thoroughly implement the important instructions of General Secretary Xi Jinping, “To make new contributions to building a beautiful Qinghai-Tibet Plateau and guarding the last pure land in the world”, and to crack the geological mysteries of the “Roof of the World” , on November 24, 2019, “Scientific Research Program of Complex Geological Processes and Resources and Environmental Effects in Qinghai-Tibet Plateau and its Surroundings (Everest Scientific Research Program )” was officially launched, which aroused widespread concern at home and abroad. From 2019 to 2030, the plan will gather top experts and scholars in related fields at home and abroad, focusing on the four main directions of the Qinghai Tibet Plateau and its surrounding areas: "formation and evolution of plateau-mountain-basin system and geodynamics", "metallogenic regularity of mineral resources and its exploration, development and utilization", "basin tectonic-sedimentary differentiation and oil and gas distribution regularity " and " geohazard prevention and ecological environment evaluation and restoration ". The plan is divided into three stages of "establishment", "construction" and "completion", which will be carried out and researched step by step, thus adding power to the construction of double first-class disciplines in our university.

The implementation of the program marks that the academic construction of Chengdu University of Technology (CDUT) has once again reached a new level. Now, one year has passed and how are the first 14 funded teams on the project progressing? What did they achieve? We interviewed several members of the team, including the chief scientist of the team, to present their research status and progress, so as to inspire our teachers and students to learn from them and strive to be the first.

Everest Scientific Research Project: Hu Wei team

Searching for traces at the disaster site to crack the mystery of long-distance high-speed landslide

In me (Hu Wei, In Chinese, hu is pronounced the same as tiger) the tiger sniffs the rose

The landslide dynamics team headed by Prof. Hu Wei in the SKLGP has been devoted to the study of catastrophic geological disasters for a long time. Now, the team has made new achievements. On May 12th(2020) , Geophysical Research Letters(GRL), the top journal in the field of geosciences, published their latest research achievement-“Study on Viscosity Weakening Characteristics of High-speed Broken Particle Flow”. This research finding is breaking some " sterotypes " in geosciences and physics, uncovering the "fog" of ultra-high-speed migration of large landslides, and laying a solid foundation for exploring the full life-cycle accompaniment mechanism of large-scale landslides. Prof. Hu said that the achievement obtained is "closely related to the new thinking and new platform brought by the Plan. "

Professor Hu Wei

"Break through the cage": the secret lies in the dust of landslide

Among the 14 Everest scientific research teams in our school, the research task of Professor Hu Wei's team is titled " Research on the Evolutionary Dynamics of High-level Long-distance Mega-hazard Formation on the Eastern Edge of Qinghai-Tibet Platuau". As one of the first funded teams, the latest scientific research achievements of the team were published in Geophysical Research Letters, a natural index journal in the field of Geosciences, shortly after the results were published. This paper, entitled "A Weakening Rheology of Dry Granular Flows with Extensible Brittle Grain Damage in High-speed Rotary Shear Experiments", has solved the core problem in the long-distance high-speed landslide- how can a huge landslide be transported at ultra-high speed and ultra-long distance, and bury a village several miles away in an instant and in the process of mountain fragmentation, why solids can flow like a fluid.

The article published in Geophysical Research Letters in May 2020 reveals the mechanism of landslide high-speed migration

The Touzhai landslide in Yunnan on September 23, 1991 is a typical case. This catastrophic accident, which killed 216 people, was caused by a huge basalt landslide. The mountain became unstable and slid into Touzhaigou at high speed, colliding with the opposite mountain slope at massive speed. Rocks were broken into large and small gravels and particles, which formed a "stone river" of about 4 kilometers, destroying the road and village. Although many scholars have conducted extensive research on Touzhai landslide, it is still an unsolved mystery why the basalt landslide with a volume of nearly 10 million cubic meters moves at such a long distance and high speed.

Before that, the field of Geosciences generally regarded the landslide in motion as a whole, and established a research system based on Coulomb friction theory (the heavier the object, the greater the pressure, the higher the shear strength of the shear plane). According to the classical physical model, the faster the particle fluid moves, the greater the shear strength of the material. However, a large number of field and experimental evidences show that the faster the migration speed of some landslides, the lower the shear strength of granular flow instead.

The contradiction between theory and reality made Hu Wei’s team even started to doubt themselves, but the answer gradually appeared in the dust of landslide.

They found a large number of nanoscale particles at the bottom of landslides in the field. In a landslide, a huge mountain may break out nanoparticles? That sounds incredible.

They no longer stuck to the traditional geological research scope, but broke through the "cage" of thinking. Hu Wei’s team introduced the particle flow theory in physics into landslide research, returning to the nature of high-speed landslide debris fluid, and to explore its internal ultra-low friction physical mechanism.

In order to clarify the relevant mechanism, the team conducted hundreds of high-speed and high-pressure granular fluid experiments. Under different conditions of high pressure and high speed, fluorite and quartz articles were crushed and scattered. The experimental results showed that for high-speed and high-pressure debris flow, the conclusion of classical physics are only valid in the low and medium speed stages. When entering high speed, the shear strength of particle flow will be greatly attenuated , the resistance will be reduced, and the velocity will be increased. For this sharp attenuation, Professor Hu Wei thought that it is the "thixotropy" of granular fluid. This is a very important insight for both geological and physical circles.

At the site of the landslide, looking for mystery of the nature

For this achievement, Hu Wei's team has visited almost all important typical landslide sites in Southwest China in recent years. At the large-scale landslide sites such as Touzhai landslide Zhaotong, Yunnan, Shuicheng landslide in Guizhou, Wenjiagou landslide in Mianzhu and Yangjiagou in Beichuan, they climbed the rocks with their bare hands, ascended one cliff face after another, and searched for the natural secrets that have been hidden for thousands of miles.

On-the-spot investigation of the massive landslide in Shuicheng, Guizhou Province

Where the landslide is, there they are.

At the site of Touzhai landslide, the research team went up the ditch to find the answer to the mystery. After nearly 30 years, the Touzhai gully is still covered with a large amount of broken accumulation bodies and huge stones caused by landslides. In order to complete the field research work within the limited weather window, the research team was divided into two groups: one is led by Professor Hu Wei, aiming at the back edge of the landslide and collecting rock and geotechnical samples along the way; the other is led by Mr. Li Yan of the School of Environment and Civil Engineering to carry out high-density electrical geophysical exploration on the accumulation body and reveal the geological structure in the depth of the landslide.

Last month, due to the sudden illness of the technical instructor of high-density electrical method, the heavy burden of field geophysical exploration fell on young teacher Li Yan the freshmenzhou li, Huang Zhihui and Bai Liang. In the sparsely populated Shan Ye, each of the several boys carried dozens of pounds of cables, laying lines more than one kilometer long on the steep slope formed by landslides. They carefully and accurately laid out 120 electrodes, dozens of connectors and measuring equipment from top to bottom, thus completing the first field exploration task perfectly.

At the landslide site in Shuicheng, Guizhou province, where 51 people died last year, the villages and houses affected by the landslide can still be found in the map software, but the site is devastated and nowhere to be found. In order to investigate the reasons why the landslide started and fluidized, the research team climbed up along the landslide and collected rock and soil samples along the way. According to the students words, it was "we should change from standing and walking to climbing mountains on all fours" just to look for precious site traces and rock and geotechnical samples.

This was also the first time that Gao Xin, a female graduate student, participated in the field geophysical exploration work. She climbed the loose soil, climbed the steep rock wall, and finally "got a glimpse of the mountains". Looking at the mountain village destroyed by the landslide, she made a decision, "I will continue to study for a doctoral degree and contribute my own strength to the cause of disaster prevention and reduction of the motherland."

Although the field work is hard, it also brings surprise to everyone.

In Touzhaigou, Zhaotong, the night has already come when the task was finished. Students were using flashlight to check and collected the equipment one by one to ensure that there was no error in the equipment and data. Although it was cold and windy in the early autumn on the plateau, there were many stars in the sky which are rare in the city. The flickering flashlight light and moonlight star light were fused together, shining in the sky like the Milky way.

In Shuicheng, a stone full of scratches on the way of climbing made everyone stop. Hu Wei led the students to "appreciate" it. "This scratched stone is like a vinyl record. The natural code hidden between scratches records the vibration information during the high-speed landslide movement, and the interpretation of these information will probably further reveal the secret of landslide fluidizationmovement.

"Chemical reaction": solving the difficult problem through the integration of various disciplines

The Everest Project has promoted the interdisciplinary development of various scientific research forces in CDUT.

Last year, the team’s paper -Superheated steam, Hot CO2 and dynamic reclamation from frictional heat joint lubricated a giant landslide: field and experimental evidence-was published on Earth And Planetary Science Letters, an internationally renowned geological journal. Soon, Nature , the international top journal, featured in an article to report the research results, and listed it as a global research highlight. In order to study the mineralogical mechanism of high-speed and long-distance landslide, the team cooperated with Associate Professor Zhang Xianghui, associate professor from the College of Materials and Chemistry and Chemical Engineering. This time, they worked closely together again because of the Everest project.

Zhang Xianghui is an expert in preparation and thermal decomposition kinetics of new functional materials. He is responsible for decomposition analysis of different mineral materials in long-distance high-speed landslide. This is the brand-new cooperation platform provided by the “Everest Project”for our school’s scientific and the cooperation of various disciplines is happening in a passionate "chemical reaction".

The Project has also promoted in-depth cooperation between research teams at home and abroad. Prior to the implementation of the Everest scientific research plan, Professor Hu Wei's team have maintained long-term cooperation with world-class scientists and various teams, including Maurice James McSaveney, a researcher at the Institute of Geology and Nuclear Sciences in New Zealand, Professor Toshi Shimamoto of Kyoto University in Japan, Professor Theo van Asch of Utrecht University in the Netherlands, Professor Jingsheng Zhang of Massachusetts University in the United States, Pierre-Yves Hicher of the French Central Institute of Technology, and Professor Wang Gonghui of Kyoto University in Japan, Researcher Janusz Wasowski of the Institute of Geology and Hydrology Protection of the National Research Council of Italy, Professor Vincenzo Del Gaudio of Bari University of Italy, to conduct joint scientific research on landslide-related mechanisms. The implementation of the Everest Plan makes their cooperation clearer and more creative.

Jointed field investigation of Yangjiagou earthquake landslide in Beichuan

In 2011, Hu Wei returned from studying abroad and joined the SKLGP. In the past 10 years, he has measured and studied several typical landslides in Daguangbao, Touzhai and Shuicheng. etc. Until last year, Prof. Hu made “the eastern edge of the Qinghai Tibet Plateau” the research focus of the project. “It can be boldly said that the eastern edge of the Qinghai Tibet Plateau is the center of landslides in the world, so it is a very correct decision to take it as the research focus of the Everest project,” Hu said.

For Hu Wei and his scientific research team, the “Everest Scientific Research Program” has opened the prelude of their “scientific research tour on the Qinghai Tibet Plateau”.

Previous research results of the team:

Prof. Hu Wei has devoted himself to the study of landslide dynamics. He has successively presided over major projects of National Natural Science Foundation, outstanding youth science fund project, general fund project, sub-project of national key research and development plan, Sichuan youth science and technology innovation team, public welfare industry special project of Ministry of Natural Resources and Sichuan outstanding youth fund project. In 2019, he won the second prize of the National Science and Technology Progress Award (ranked sixth); In 2015, he won China Youth Geological Science and Technology Award - Silver Hammer Award; In 2019, he was selected as one of the Tianfu Ten Thousand Talents Plan of Sichuan Province; In 2017, he was selected as one of the outstanding young scientific and technological talents of the Ministry of Natural Resources; The related achievements were published in seven journals of Nature Index, such as Geography, Earth and Planetary Science letters, Geophysical Research Letters (5 articles), etc. A total of 7 papers have been published in SCI Index journals, including 7 papers in Nature Index and 15 papers in the first division of the Chinese Academy of Sciences.

Achievement and international evaluation:

The related research achievements have made important progress in the disaster factors of high-speed and long-distance landslides and the mechanism of high-speed and long-distance migration. The research team has made new discoveries and new viewpoints in many aspects, especially the discovery of the field and experimental evidence of high-temperature thermal decomposition of high-speed and long-distance landslide, proposed an accurate method to determine the sliding zone temperature based on thermogravimetric analysis and thermal decomposition mineral stratification analysis, revealed thedrag reduction mechanism of high-pressure gas and dynamic recrystallization , and found the landslide deformation and failure mechanism and key disaster-causing factors. It is worth mentioning that the paper "superheated steam, hot CO2 and dyn amic reconstruction from frictional heat jointly constructed a giant landscape: field and experimental evidence" published in Earth and Planetary Science Letters has attracted the attention of all parties. Nature , an internationally renowned journal, wrote a special article on it, and listed this research as a global research hotspot (

The article in Nature pointed out that by combining field experiment with indoor high-speed friction experiment, the research team led by Professor Huang Runqiu of Chengdu University of Technology revealed that the high temperature at the bottom of Daguangbao landslide during sliding process could reach 850 degrees Celsius. Under the action of high temperature, minerals decompose to produce a large amount of gas. These gases and water vapor form high-pressure gases in the dense sliding zone. High pressure gas and dynamic recrystallization layer act together to form ultra-low friction at the bottom of large landslide. This study can well explain the mechanism of high-speed and long-distance motion of large landslides.On the internationally renowned landslide Blog of American National Geosciences Association (AGU), Professor Dave Petly, vice president of Sheffield University and internationally renowned landslide expert, wrote an article to report the study. In particular, this report points out that it is an extraordinary contribution that this study reveals that the motion behavior of the 200 million-square-meter giant landslide is controlled by a 0.1mm thick dynamic recrystallization layer. The link to this report is

Professor Dave Petly, an internationally renowned landslide expert, wrote an article to report the study