To investigate frictional properties of the rupture surface of the
carbonate Jiweishan rock avalanche, we conducted high-velocity-friction
tests at different shear rates. The samples showed shear- and
rate-strengthening of friction at low shear rates, but transformed to
shear- and rate-weakening of friction at large shear rates. The friction
coefficient reduced to an extremely low value of less than 0.1. The
sliding rock mass therefore could slide out of the rupture surface at a
high velocity and consequently traveled a long distance as granular
debris. Two mechanisms may have reduced the frictional resistance.
Recrystallized calcite nanograins and CaO nanograins produced through
calcite decomposition covered and lubricated the shear surface.
Furthermore, the CO emitted through calcite decomposition reduced the
effective normal stress and therefore the friction on the surface. Our
conclusions for Jiweishan rock avalanche are also useful for
understanding the high mobility of other widely distributed carbonate
rock avalanches.