Understanding and Predicting Landslides

In recent years, an increasing number of natural slope failures caused by long-lasting heavy rainfall events have been observed all over the world, which often end with a catastrophic loss of human lives and destruction of buildings.

These researchers, based at the Institute of Applied Mechanics, Stuttgart, Germany, have attempted to use computational investigations of the complex flow and deformation processes of natural slopes to predict slope movements and slope failure situations caused by heavy rainfall events.

Numerical simulations of hillsides and slopes can support the detection of various failure mechanisms by changing the initial and boundary conditions of the considered initial situation.

The procedure they use can contribute to a deeper and better understanding of various complex slope failure processes. In their study, the slope system, generally understood as an unsaturated soil, was considered as a triphasic material consisting of a soil skeleton, such as sand, a pore liquid, such as water, and a pore gas, such as air.

The computer model used was based on the theory of porous media and numerical solutions were achieved software designed for the solution of strongly coupled multiphasic porous media problems in solid-fluid interaction, called PANDAS.

Starting with cohesionless sand as the basic soil under study, the material parameters governing the soil behavior were taken from triaxial experiments on dry sand specimens performed under homogeneous loading conditions, whereas the parameters governing the hydraulic behavior were determined by experiments on saturated soil specimens under non-deforming conditions.

In addition, numerical investigations of slope failure scenarios under different loading conditions were compared with each other to find out how the pore water influences the failure behavior.

According to the researchers, the application of computer simulations to reveal the complex hydraulic pressure and flow systems that might trigger hillslope movements also poses challenges to the numerical algorithms. In fact, the numerical treatment of strongly coupled, inelastic solid–fluid initial-boundary value problems on real-scale, three-dimensional domains requires high computing power exploiting very complex parallel and distributed solution strategies.

The computations reveal a strong coupling between the soil deformation and the hydraulic behavior during failure processes. The researchers compared their modeled flow and deformation behavior to hillside situated near Dornbirn in the eastern part of the Voralberg Alps (Austria).

Material summarized from:

Computation of Slope Movements Initiated by Rain-Induced Shear Bands in Small-Scale Tests and In Situ
W. Ehlers, O. Avci, and B. Markert
doi:10.2136/vzj2009.0156. Published online 20 Oct. 2010 in Vadose Zone J.
 

https://www.soils.org/files/publications/vzj/abstracts/v09-0156-abstract.pdf

Vadose Zone Journal is published by the Soil Science Society of America.
Cooperator: Geological Society of America.