Abstract. Although slow-moving landslides represent a substantial
hazard, their detailed mechanisms are still comparatively poorly understood.
We have conducted a suite of innovative laboratory experiments using novel
equipment to simulate a range of porewater pressure and dynamic stress
scenarios on samples collected from a slow-moving landslide complex in New
Zealand. We have sought to understand how changes in porewater pressure and
ground acceleration during earthquakes influence the movement patterns of
slow-moving landslides. Our experiments show that during periods of elevated
porewater pressure, displacement rates are influenced by two components:
first an absolute stress state component (normal effective stress state)
and second a transient stress state component (the rate of change of normal
effective stress). During dynamic shear cycles, displacement rates are
controlled by the extent to which the forces operating at the shear surface
exceed the stress state at the yield acceleration point. The results
indicate that during strong earthquake accelerations, strain will increase
rapidly with relatively minor increases in the out-of-balance forces.
Similar behaviour is seen for the generation of movement through increased
porewater pressures. Our results show how the mechanisms of shear zone
deformation control the movement patterns of large slow-moving
translational landslides, and how they may be mobilised by strong
earthquakes and significant rain events.
Displacement mechanisms of slow-moving landslides in response to changes in porewater pressure and dynamic stress
