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Research Team of prof. Cheng Qiangong Published in the Internationally Renowned Geoscience Journal JGR: Solid Earth and the Publication was Selected as "research focus" of the Academic Paper

High-speed remote landslide (rock avalanches, sturzstorms), as an extremely destructive geological hazard phenomenon, often shows a huge volume (generally more than millions of square, up to tens of millions of square or even billions of square) and extraordinary high speed (so far, It is known that the maximum speed of two high speed remote landslides is 213 m/s and 278 m/s, respectively). The unpredictable eccentricity (the maximum horizontal slip is 30 times the maximum vertical drop hmax, or even larger, and the Lmax can reach several kilometres or even hundreds of kilometres), huge energy (for example, during the movement, the mass can often be thrown up and climb over a fairly high hillside, and the maximum climb can reach 640 m), unusually high mobility, and many other "amazing" and "puzzling" phenomenon. Therefore, the key scientific problems involved in the research of high speed remote landslide are solving the following challenges: How fast is the maximum speed for a single high-speed remote landslide event? How far is the maximum distance? What is the coverage area and the influence range of the clastic fluid accumulation? What is the reason for the high speed and low friction remote movement of giant landslides?

 

The giant high-speed remote landslide developed in China's Tibetan plateau is a natural laboratory for the study of its dynamical mechanism. After Dr. Wang Yufeng (Southwest Jiaotong University) and Professor Dong Jiajun of Taiwan Central University, and Professor Cheng Qianggong (southwest Jiaotong Univ), we have obtained the following conclusions and understandings through a series of rotational shearing experiments on the bottom facies (basal facies) of the Yigong landslide deposits in Tibet.

 

(1) The bottom phase specimen of high speed remote landslide shows obvious velocity dependent weakening characteristic, when the shear rate exceeds 0. The equivalent friction coefficient of the specimen is rapidly reduced to 0.13, which is far lower than the residual friction coefficient of the specimen in the direct shear Test (2) under the High speed shearing condition (veq≥0. m/s), The frictional heat will cause the rapid increase of the temperature value of the specimen shear zone, resulting in the vaporization of the water molecule in the specimen, the formation of high density stomatal layer in the shear zone, and the activation energy of the fine particles and aqueous molecules in the sample. (3) The phenomenon of hot pressing and molecular activation caused by frictional heat in the specimen shearing process is an important reason for the obvious weakening of the dynamic shear properties of the specimen.


 


Figure 1  The location of high-speed remote landslide in Yigong


Figure 2 Apparent friction coefficient as a function of equivalent shearing velocity. 

 


The research was funded by the National Science Foundation of China and published in the Journal of Geophysical Research: the Solid earth. The Journal of Geophysical Research, Journal of Geophysical, was launched in 1896 as one of the most authoritative journal in the field of Earth sciences by the American Geophysical Society (American Geophysical Union, AGU), and the JGR: Solid Earth is the natural Index (Nature Index) and selected as one of the 68 world's first-class scientific research journals (geoscience includes JGR: Solid Earth in only 6 kinds of journals). Scholars in China and abroad, even at famous universities like Harvard and Stanford, if published in the JGR Journal in the field of geology, are often recognized as high academic achievement.

In the field of international high-speed remote landslide dynamics research, a large part of the important original theory or model experimental results have been published in this journal. The publication of research team of Professor Cheng is a new development in the field of high speed remote landslide dynamics research in our school. As the results of the study on the "Thorny Problem (Teaser)", in the field of landslide dynamics, the JGR editorial board rated this publication as the best paper in "Broad Earth and space science field" and “study Spotlight”, and the publication was published in the Earth and Space science News (Eos). ,

 

In a recent online journal of the Earth and Space Science News (Eos), the freelance contributor commented: "The results have implications for researchers in many geologic disciplines, including landslide dynamics, earthquake mechanics, and risk assessment ".

 

Paper Details:wang,y.f.,j.j.dong,andq.g.cheng(2017),velocity-dependentfrictionalweakeningoflargerockavalanchebasal Facies: Implications for Rock Avalanche hypermobility, J. Geophys. Res. Solid Earth, $number, doi: 1002/2016jb013624.

 

Article link: http://onlinelibrary. Wiley. Com/doi/10.1002/2016jb013624/full

 

Comment Link: https://eos. org/

 

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