10.1 Landslides risk analysis using a newly developed scalable and extensible geo-fluid model (2008

10.1

Landslides risk analysis using a newly developed scalable and extensible geo-fluid model

Diandong Ren, Univ. of Oklahoma/CAPS, Norman, OK; and D. J. Karoly and L. M. Leslie

In this study, we investigate landslide potential, using a new constitutive relationship for

granular flow in a numerical model. Unique to this study is an original relationship between soil

moisture and the inertial number for soil particles. Our numerical model can be applied to

arbitrary soil slab profile configurations and to the analysis of natural disasters, such as

mudslides, glacier creeping, avalanches, landslips and other pyroclastic flows. Here we focus

on mudslides.

We examine the effects of bed slope and soil slab thickness, soil layered profile

configuration, soil moisture content, basal sliding and the growth of vegetation, and show that

increased soil moisture enhances instability primarily by decreasing soil strength, together with

increasing loading. Moreover, clay soils generally require a smaller relative saturation than sandy

soils for sliding to commence. For a stable configuration, such as a small slope and/or dry soil,

the basal sliding is absorbed if the perturbation magnitude is small. However, large perturbations

can trigger significant scale mudslides by liquefying the soil slab.

The role of vegetation depends on the wet soil thickness and the spacing between vegetation

roots. The thinner the saturated soil layer, the slower the flow, giving the vegetation additional

time to extract soil moisture and slow down the flow. By analyzing the effect of the root system

on the stress distribution, we show that closer tree spacing increases the drag effects on the

velocity field, provided that the root system is deeper than the shearing zone.

Finally, we investigated a two-layer soil profile, namely sand above clay. A significant stress

jump occurs at the interface of the two media.