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| Titel |
Forecasting landslide motion by a dynamic elasto-visco-plastic model |
| VerfasserIn |
Marco Secondi, Giovanni B. Crosta, Claudio di Prisco, Gabriele Frigerio, Paolo Frattini, Federico Agliardi |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250057895
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| Zusammenfassung |
| Forecasting landslide motion by a dynamic elasto-visco-plastic modelMany slopes are
subjected to continuous movement and intermittent stages of slowing and accelerating
motion. Various authors (Angeli et al., 1996; Butterfield, 2000, Corominas et al., 2005,
Gottardi and Butterfield, 2001, Van Asch et al., 2007, Ranalli et al., 2010) used different
approaches to study this problem and we propose a new model in this contribution. We
presents a 1D elasto-visco-plastic model that assumes a frictional behaviour for an infinite
slope: the sliding mass is assumed to move as a rigid body and the slope movements are
concentrated within a narrow basal shear zone. The pre-existing surface is considered at
residual strength conditions and includes a visco-plastic behaviour to take into account both
dynamic-inertial and viscous effects. In order to reproduce this behaviour, a Newmark
pseudo-static approach is adopted, starting from the Perzyna’s visco-plasticity theory.
This approach allows to take into account the “delayed plasticity due only to the
evolution of the soil micro-structure after a load increment (e.g. water table oscillation).
This type of plasticity is characterised by a different time-scale from consolidation
induced plasticity. As the elastic response is assumed instantaneous, the plastic
deformations are associated to a time-dependent evolution. The dynamic formulation
of this approach is introduced by means of a simple equation that allows to take
into account the landslide velocity. Thus, the slope is no longer characterised by a
rigid and perfectly plastic behaviour but by a simple rigid-plastic one. Moreover,
the shear resistance does not change during the evolution process of deformation
and with the load increment velocity, so that hardening and softening behaviours
are not taken into account. In order to describe the evolution of the visco-plastic
deformations, three different viscous nucleus formulations have been adopted. A
linear and rigid-plastic nucleus, in which irreversible deformations occur only if the
plasticity surface is positive (and thus only if the acting force is higher than the
resisting one). A second linear formulation, in which visco-plastic deformation always
occurs. The third nucleus is an exponential and positive one which can take into
account both high and small deformations increments. The viscosity of the proposed
model is derived on the basis of a visco-plastic constitutive model. Other authors
assumed more simple viscous fluids behaviours (Bingham type, Ledesma et al., 2009,
Ranalli et al., 2009) or proposed theoretical power law models based on mathematical
relationships relating the viscous forces to the system velocities (Ledesma et al.,
2009).
To test the model with the different proposed formulations we used datasets from the
literature (see above listed references) and a long term monitoring dataset from the
Bindo-Cortenova landslide site (Italian Prealps, Lake of Como, Lombardy, Italy). This last
site is characterized by a large and active slope failure located in the. Different landslides
(June 1987, November 2000, May 2001) took place along the entire slope interested by large
landslide (consisting of a permian conclomerate, immersed in a matrix of gravely sand). The
toe of the slope underwent a catastrophic failure in december 2002 after a period
of extremely heavy rainfall (1500-2000 mm/year, ca. 50To predict the landslide
mechanical behaviour and define displacement thresholds caused by heavy rainfall, we
adopted a constitutive modelling approach for the material involved. After calibration
procedures, the computed evolution of deformations has been compared to ground
displacement data given both by the on-site monitoring system and inSAR monitoring
system.
Angeli MG, Gasparetto P, Menotti RM, Pasuto A, Silvano S (1996) A visco-plastic model
for slope analysis applied to a mudslide in Cortina d’Ampezzo, Italy. Q J Eng Geol
29:233–240 Butterfield R (2000) A dynamic model of shallow slope motion driven by
fluctuating groundwater levels. Proceedings of the 8th International Symposium on
Landslides.Thomas Telford, London, vol 1, pp 203–208 Corominas J, Moya J, Ledesma A,
Lloret A, Gili JA (2005) Prediction of ground displacements and velocities from groundwater
level changes at the Vallcebre landslide (Eastern Pyrenees, Spain). Landslides 2:83–96
Gottardi G, Butterfield R (2001) Modelling ten years of downhill creep data, vol. 1–3.
Proceedings of the 15th International Conference on Soil Mechanics and Geotechnical
Engineering. Istanbul, Turkey, pp. 27–31 Van Asch TWJ, Van Beek LPH, Bogaard TA (2007)
Problems in predicting the mobility of slow-moving landslides. Eng Geol 91:46–55 Ranalli ,
M., Gottardi, G., Medina-Cetina , Z., Nadim, F. (2010) Uncertainty quantification in the
calibration of a dynamic viscoplastic model of slow slope movements. Landslides
7:31–41 |
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