a School of Civil Engineering, Sun Yat-sen University, Zhuhai, 519082, China
b State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou, 221116, China
c Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, 519082, China
2022, 14(3): 746-756. doi:10.1016/j.jrmge.2021.09.011
Received: 2021-07-05 / Revised: 2021-08-18 / Accepted: 2021-09-09 / Available online: 2021-11-20
2022, 14(3): 746-756.
doi:10.1016/j.jrmge.2021.09.011
Received: 2021-07-05
Revised: 2021-08-18
Accepted: 2021-09-09
Available online: 2021-11-20
The dynamic frictional behaviors of natural discontinuities (joints, fractures, faults) play an important role in geohazards assessment; however, the mechanisms of the dynamic fault weakening/strengthening are still unclear. In this paper, a dynamic shear box was used to perform direct shear tests on saw-cut (planar) and natural (rough) granite fractures, with different normal load oscillation amplitudes. Based on the recorded shear forces and normal displacements, the shear forces, apparent friction coefficients and normal displacements are found to change periodically with oscillated normal loads and are characterized by a series of time shifts. The observed changing patterns are similar for the rough and planar fractures. Compared with the test data under constant normal load (CNL), small/large normal load oscillation amplitude enhances/reduces the peak shear strength, with a critical point. The magnitude of critical normal load oscillation for the rough fractures is smaller than the planer fractures. The results imply that dynamic fault weakening/strengthening can be achieved by both normal load oscillation amplitudes and slip surface topography. The rough fractures with larger normal oscillation amplitude can easily cause frictional weakening under stress disturbance.
Keywords: Direct shear test, Normal load oscillation fracture roughness, Critical oscillation amplitude, Dynamic weakening/strengthening
Wengang Dang
Dr. Wengang Dang obtained his BSc degree in Mining Engineering from China University of Mining and Technology, Xuzhou in 2010. He received his PhD degree from the TU Bergakademie Freiberg, Germany in 2017. Since 2019, he has been employed as an Associate Professor in the School of Civil Engineering at the Sun Yat-sen University. His work focuses on experimental rock mechanics in relation to geothermal injection induced earthquake and shear behavior of geological bodies under dynamic disturbance.