Ferri, Fabio and Di Toro, Giulio and Hirose, Takehiro and Han, Raehee and Noda, Hiroyuki and Shimamoto, Toshihiko and Quaresimin, Marino and de Rossi, Nicola (2011) Low- to high-velocity frictional properties of the clay-rich gouges from the slipping zone of the 1963 Vaiont slide, northern Italy. Journal of Geophysical Research B, 116 . B09208. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20111025-090004241
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The final slip of about 450 m at about 30 m/s of the 1963 Vaiont landslide (Italy) was preceded by >3 year long creeping phase which was localized in centimeter-thick clay-rich layers (60–70% smectites, 20–30% calcite and quartz). Here we investigate the frictional properties of the clay-rich layers under similar deformation conditions as during the landslide: 1–5 MPa normal stress, 2 × 10^(−7) to 1.31 m/s slip rate and displacements up to 34 m. Experiments were performed at room humidity and wet conditions with biaxial, torsion and rotary shear apparatus. The clay-rich gouge was velocity-independent to velocity-weakening in both room humidity and wet conditions. In room humidity experiments, the coefficient of friction decreased from 0.47 at v < 5.0 × 10^(−5) m/s to 0.12 at 1.31 m/s. Microstructural and mineralogical analyses of the gouge after experiments indicate that the dramatic weakening results from thermo-chemical pressurization of pore fluids (smectite decomposition to illite-type clays) and powder lubrication. In wet experiments, the coefficient of friction decreased from 0.17 at v < 1.0 × 10^(−4) m/s to 0.0 at v > 0.70 m/s: full lubrication results from the formation of a continuous water film in the gouge. The Vaiont landslide occurred under wet to saturated conditions. The unstable behavior of the landslide is explained by the velocity-weakening behavior of the Vaiont clay-rich gouges. The formation of a continuous film of liquid water in the slipping zone reduced the coefficient of friction to almost zero, even without invoking the activation of thermal pressurization. This explains the extraordinary high velocity achieved by the slide during the final collapse.
|Additional Information:||© 2011 American Geophysical Union. Received 3 March 2011; accepted 5 July 2011; published 28 September 2011. F.F. was supported by CARIPARO (Cassa di Risparmio di Padova e Rovigo) project and G.D.T. by a European Research Council Starting grant 205175 (USEMS). Author contributions are as follows: F.F. and G.D.T. wrote the manuscripts; G.D.T., F.F., T.S. and M.Q. designed the experiments; F.F., T.H., H.N., R.H. and N.D.R. carried out the experiments; F.F. performed the microstructural and mineralogical investigations. G.D.T. thanks David Lockner for enlightening discussions on lubrication in wet clays and Rinaldo Genevois for friendly review of the manuscript. The careful reading and comments by reviewers Diane Moore and Ernie Rutter greatly improved the manuscript.|
|Subject Keywords:||Vaiont; friction; gouge; landslide; smectite; thermal pressurization|
|Official Citation:||Ferri, F., G. Di Toro, T. Hirose, R. Han, H. Noda, T. Shimamoto, M. Quaresimin, and N. de Rossi (2011), Low- to high-velocity frictional properties of the clay-rich gouges from the slipping zone of the 1963 Vaiont slide, northern Italy, J. Geophys. Res., 116, B09208, doi:10.1029/2011JB008338.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||25 Oct 2011 20:06|
|Last Modified:||26 Dec 2012 14:19|
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