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Shear Resistance Variations in Experimentally Sheared Mudstone Granules: A Possible Shear‐Thinning and Thixotropic Mechanism
Author(s) -
Hu Wei,
Xu Qiang,
Wang Gonghui,
Scaringi Gianvito,
Mcsaveney Mauri,
Hicher PierreYves
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl075261
Subject(s) - thixotropy , shear (geology) , geology , geotechnical engineering , landslide , shear rate , shear thinning , shear zone , direct shear test , rheology , thinning , materials science , mineralogy , composite material , petrology , tectonics , seismology , ecology , biology
We present results of ring shear frictional resistance for mudstone granules of different size obtained from a landslide shear zone. Little rate dependency of shear resistance was observed in sand‐sized granules in any wet or dry test, while saturated gravel‐sized granules exhibited significant and abrupt reversible rate‐weakening (from μ = 0.6 to 0.05) at about 2 mm/s. Repeating resistance variations occurred also under constant shear displacement rate. Mudstone granules generate mud as they are crushed and softened. Shear‐thinning and thixotropic behavior of the mud can explain the observed behavior: with the viscosity decreasing, the mud can flow through the coarser soil pores and migrate out from the shear zone. This brings new granules into contact which produces new mud. Thus, the process can start over. Similarities between experimental shear zones and those of some landslides in mudstone suggest that the observed behavior may play a role in some landslide kinematics.