Relations between hydrology and velocity of a continuously moving landslide—evidence of pore-pressure feedback regulating landslide motion?

Abstract

We measured displacement, pore-water pressure, and climatic conditions for 3 years at the continuously moving Slumgullion landslide in Colorado, USA. The landslide accelerated when pore-water pressure increased within the landslide body, but this occurred as pore-water pressure decreased along the landslide margin. The decrease probably occurred in response to shearinduced soil dilation at rates greater than pore-pressure diffusion and likely increased resistance to shear displacement and resulted in landslide deceleration. This dilative strengthening has been experimentally observed and explained theoretically, but not previously identified during field studies. Although landslide displacement should have exceeded that required to achieve critical-state density of shear boundaries, observed relocation of these boundaries indicates that shearing is episodic at fixed locations, so it permits renewed dilative strengthening when "fresh" soil is sheared. Thus, dilatant strengthening may be a considerable mechanism controlling landslide velocity, even for landslides that have continuously moved great distances.

Rate-weakening friction characterizes both slow sliding and catastrophic failure of landslides

“…Such models are able to describe both slow sliding and catastrophic failure because dilatant strengthening occurs only until a critical-state porosity is reached; subsequent consolidation can trigger catastrophic failure. Hence, although dilatant effects can be significant in particular cases (10), their ability to regulate the speeds of repeated slow-moving landslides is diminished if the shear-zone material cannot consolidate gradually between slip events.…”

Mechanical state of gravel soil in mobilization of rainfall-induced landslides in the Wenchuan seismic area, Sichuan province, China

“…The variation of mechanical state, such as the transformation from a relatively stable state to a critical state, has been commonly used to analyze the initiation of landslides (Iverson et al, 2010(Iverson et al, , 2000Liang et al, 2017;Sassa, 1984;Schulz et al, 2009). Therefore, a deep understanding of the soil state is the scientific basis for the study of landslide occurrence (Chen et al, 2017).…”

“…Since the 1980s, critical state soil mechanics has received extensive attention (Fleming et al, 1989;Gabet and Mudd, 2006;Iverson et al, 2000). Some of the observed landslides, such as the Salmon Creek landslide in Marin County (Fleming et al, 1989), Slumgullion landslide in Colorado (Schulz et al, 2009), and Guangming New Distinct landslide in Shenzhen (Liang et al, 2017), could be approximately explained by this theory. Based on the F line drawn by Casagrande (1936), Fleming et al (1989) found that the increase in pore water pressure contributed to the dilation and caused the debris flow characterized by the intermittent movement.…”

“…The formula of the void ratio was derived, which was the function of the mean effective stress (Gabet and Mudd 2006). Schulz et al (2009) found out that the dilative strengthening might control the velocity of a moving landslide through the hourly continuous measurement of displacement of landslides. Liang et al (2017) found that the initial solid volume fraction affected the soil state of the granular-fluid mixture.…”

Characterization of groundwater dynamics in landslides in varved clays

“…Reid and Iverson, 1992;Iverson, 2000;Wilkinson et al, 2002;Lindenmaier et al, 2005;Schulz et al, 2009;Wienhöfer et al, 2010;Bogaard et al, 2012). As a result, the effects of changes in climate or land use on landslide occurrence are difficult to predict (e.g.…”