Acute Sensitivity of Landslide Rates to Initial Soil Porosity
R. M. Iverson,1
M. E. Reid,2
N. R. Iverson,3
R. G. LaHusen,1
M. Logan,1
J. E. Mann,3
D. L. Brien2
Some landslides move imperceptibly downslope, whereas
others accelerate catastrophically. Experimental landslides triggered by rising pore water pressure moved at sharply contrasting rates due to
small differences in initial porosity. Wet sandy soil with porosity of
about 0.5 contracted during slope failure, partially liquefied, and
accelerated within 1 second to speeds over 1 meter per second. The same
soil with porosity of about 0.4 dilated during failure and slipped
episodically at rates averaging 0.002 meter per second. Repeated slip
episodes were induced by gradually rising pore water pressure and were
arrested by pore dilation and attendant pore pressure decline.
1 U.S. Geological Survey, 5400 MacArthur
Boulevard, Vancouver, WA 98661, USA.
2 U.S.
Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, USA.
3 Department of Geological and Atmospheric Sciences,
Iowa State University, Ames, IA 50011, USA.
