Study on Dynamic Response and Progressive Failure of Rock Slope under Strong Earthquakes

Shengwen Qi
Institute of Geology and Geophysics, Chinese Academy of Sciences

Shengwen Qi^1,2,3, Bowen Zheng^1,2,3, Jianxian He⁴, Zhifa Zhan⁵, Guoxiang Yang⁵
1. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
2. University of Chinese Academy of Sciences, Beijing 100049, China.
3. Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China.
4. Department of Geotechnical Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China.
5. China University of Geoscience, Beijing, 100081, China.

Abstract: Seismic landslides are the most common secondary disasters of strong earthquakes. The study of dynamic response and progressive failure of rock slope under strong earthquakes has always been the focus of scientific and engineering fields in China and the world. The dynamic shear characteristics of the rock discontinuities are of great importance to evaluate the seismic stability of rock slope. We have carried out series direct shear tests to investigate dynamic properties for persistent rock discontinuities under seismic waves with a new developed dynamic direct shear testing device on rock joints as reported in Qi et al (2020). It has been found that seismic shear strain rate has a remarkable influence on the resistance of discontinuities, and the shear behavior of discontinuities under the seismic wave loads has a notable difference between their in the quasi static condition. The shear strength of granite, syenite and concrete discontinuities shows an increasing trend with the increase of shear rate. The shear strength of sandstone, cement and gypsum discontinuities displays a decreasing tendency with the increase of shear rate. The rate effect for shear strength of discontinuities shows a strengthening trend with the increase of discontinuity initial undulation roughness and discontinuity wall compressive strength. There is a weakening tendency of the rate effect for shear strength of discontinuities with the increase of normal stress and discontinuity size. The degradation of discontinuity morphology changes non-linearly with the increase of cumulative shear displacement. We put forward an advanced shear strength criterion of discontinuities taking into account the rate effect, cyclic effect and size effect simultaneously.

We adopted iron powder, barite powder, quartz sand, gypsum and water as similar materials to conduct the shaking table test of large homogeneous rock slope. The dynamic properties of artificial discontinuities have also been investigated with the apparatus mentioned above. A series of shaking table tests have been performed to comprehensively investigate the seismic response characteristics of the homogeneous, bedding-plane and anti-dip rock slopes. Meanwhile, Results reveal that peak ground motion acceleration amplification factor (AAF) generally increases with the increasing of the slope elevation. Meanwhile, the seismic response of the slope has a dependent effect on the frequency or loading rate of the input motions. The AFF reaches remarkable value when the input frequency is near to natural frequency of the slope while there shows no amplification when the loading frequency is larger than natural frequency. The structure of the slope has a significant effect on the seismic response of the slope, showing the strongest of the bedding-plane slope, followed by homogeneous slope and the weakest anti-dip slope. The progressive failure of the slope can be characterized by four stages with the increasing of the seismic loading amplitudes, which is accordance with the degrading of the natural frequency of the slope. The dynamic slip surface of the homogeneous is shallow near the slope crest, the bedding-plane is along the planes and the anti-dip slope is a curved-linear at the upper slope surface.

Bio: Shengwen Qi is a professor and Ph.D. supervisor at the Institute of Geology and Geophysics, Chinese Academy of Sciences. He mainly researches the seismic dynamic response of rock slope, the dynamic effect of rock mass structure and the genetic mechanism of gravity deformation of high rock slope. Prof. Qi is also the Chairman of Committee for structure and behavior of Soil and Rock mass (C29) of International Association for Engineering Geology and the Environment (IAEG), Secretary-General of IAEG Chinese Committee, Member of IAEG Youth Committee, Life Council Member of International Consortium on Geo-Disaster Reduction (ICGDR), Director of the Key Laboratory of Shale Gas and Geological Engineering of Chinese Academy of Sciences, Secretary-General of Engineering Geology Committee of Chinese Geological Society. Standing Member of Chinese Society of Rock Mechanics and Engineering, Vice Chairman of Rock Dynamics Committee, Editorial board member of Engineering Geology, Bulletin of Engineering Geology and the Environment, and other authoritative journals in the field of Engineering Geology. Prof. Qi has presided over more than 20 national basic research projects, science and technology research projects aimed at the key task, as well as projects entrusted by national large enterprises, including 1 special task of scientific and technological basic resources investigation, 1 outstanding youth project, 1 excellent youth project of National Natural Science Foundation of China, 1 major project topic, 3 general projects, 1 strategic pilot special project (Class A) project of CAS, 1 key deployment project of CAS; Prof. Qi has published more than 200 papers and his papers have been cited for more than 4000 times. He has published 8 monographs, developed 1 set of research equipment, and authorized more than 20 patents. Prof. Qi has been awarded the title of Leading Talent of Science and Technology Innovation in the National Ten Thousand Talents Program in 2018, Richard Wolters Prize of IAEG(Runner up) in 2014, and the First Prize of Natural Science of China Society of Rock Mechanics and Engineering in 2020, etc.