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| Titel |
Effect of unstable layer depth on the pore pressure distribution, case study of the Slano Blato landslide (Slovenia) |
| VerfasserIn |
Amin Askarinejad, Bandar Secchi, Matej Macek, Ana Petkovsek, Sarah Springman |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083189
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| Zusammenfassung |
| The Slano Blato landslide is one of the largest landslides in Slovenia with a volume of more
than 1 mio m3 of moving debris. The landslide is located at the border of Triassic
limestone and Eocene flysch formations. Flysch is composed of layers of marls and
sandstones. The sliding mass consists mainly of clay and clayey gravel of highly
weathered and deteriorated flysch, while a minor part represents grains and blocks of
limestones. (Petkovšek et al., 2009). The first documentation of an instability event
dates back to 1789 and the landslide was reactivated during a heavy rain period in
November 2000. Since then, the ground surface level above the unstable material on the
upper zones of the landslide is significantly decreasing so that the current slope
surface is now more than 10 m below the terrain surveyed in 1998. The new landslide
topography results in different pore pressure distributions in the slope, which were
anticipated to have a detrimental effect on the stability and movement regime of the
slope.
The main goal of this work is to investigate the effect of the overlying debris depth on the
pore water pressure distribution during a predefined precipitation scenario. The behaviour of
the unsaturated soil and the effects of fissures in the bedrock are also considered in the
analysis. Hydro-mechanical simulations were performed using 2D finite element software
(PLAXIS) and numerical results are compared with results from analytical models, which use
a 1D steady state formulation for the hydraulic part and a 2D limit equilibrium approach to
calculate the safety factors.
The numerical studies show significant change in the pore water pressure distribution in
the landslide body with variation of the debris depth. An increase in the debris depth leads to
higher suction due to the deeper location of the water table. Higher suction increases
landslide stability due to: i) increase of the effective stress and hence the shear
strength of the material and ii) decrease of the unsaturated hydraulic conductivity.
Accordingly, a longer rainfall event with a similar intensity is required to destabilize the
slope.
The calculated suction profile for the current slope surface was compared to the in situ
measurements, and the results show partial agreement. The slight discrepancy might be
attributed to several factors such as: i) possible difference in the height of the water table in
the model and reality, ii) differences in location between observation points in numerical
model and in-situ observations, as there are no tensiometers in the upper part of the slope, iii)
modelling the underlying flysch layer as a homogenous and isotropic material in PLAXIS,
which is not the case in reality.
Reference:
Petkovsek, A., Macek, M., Kocevar, M., Benko, I., Majes, B., 2009. Soil matric
suction as an indicator of the mud flow occurrence. 17th International Conference of
Soil Mechanics and Geotechnical Engineering, Alexandria, Egypt, 1855 - 1860. |
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