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Velocity‐dependent frictional weakening of large rock avalanche basal facies: Implications for rock avalanche hypermobility?
Author(s) -
Wang Y. F.,
Dong J. J.,
Cheng Q. G.
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013624
Subject(s) - shearing (physics) , geotechnical engineering , materials science , geology , shear (geology) , debris , composite material , oceanography
To characterize the hypermobility mechanism of rock avalanches, a series of rotary shear tests at different shearing velocities ( V eq ) ranging from 0.07 m/s to 1.31 m/s and at a normal stress of 1.47 MPa were carried out on soil sampled from the basal facies of the Yigong rock avalanche that occurred in the Tibetan plateau in China. Through conducting these tests, the macroscale and microscale features of the deformed samples were analyzed in detail with the following valuable conclusions being reached: (1) soil subjected to rotary shear exhibits a clear velocity‐dependent weakening characteristic with an apparent steady state friction of 0.13 being reached at V eq ≥ 0.61 m/s, (2) high‐temperature rises and layers with high porosity were observed in the samples sheared at V eq ≥ 0.61 m/s, and (3) the cooperation of thermal pressurization and moisture fluidization induced by friction heating plays an important role in explaining the marked frictional weakening of the soil. In addition, the appearance of nanoparticles due to particle fragmentation should facilitate the weakening of the soil but is not the key reason for the marked frictional weakening.