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| Titel |
Large-scale field testing on flexible shallow landslide barriers |
| VerfasserIn |
Louis Bugnion, Axel Volkwein, Corinna Wendeler, Andrea Roth |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042031
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| Zusammenfassung |
| Open shallow landslides occur regularly in a wide range of natural terrains. Generally, they
are difficult to predict and result in damages to properties and disruption of transportation
systems.
In order to improve the knowledge about the physical process itself and to develop new
protection measures, large-scale field experiments were conducted in Veltheim, Switzerland.
Material was released down a 30- inclined test slope into a flexible barrier. The flow as well
as the impact into the barrier was monitored using various measurement techniques. Laser
devices recording flow heights, a special force plate measuring normal and shear basal forces
as well as load cells for impact pressures were installed along the test slope. In addition, load
cells were built in the support and retaining cables of the barrier to provide data for
detailed back-calculation of load distribution during impact. For the last test series an
additional guiding wall in flow direction on both sides of the barrier was installed to
achieve higher impact pressures in the middle of the barrier. With these guiding walls
the flow is not able to spread out before hitting the barrier. A special constructed
release mechanism simulating the sudden failure of the slope was designed such that
about 50Â m3 of mixed earth and gravel saturated with water can be released in an
instant.
Analysis of cable forces combined with impact pressures and velocity measurements
during a test series allow us now to develop a load model for the barrier design. First
numerical simulations with the software tool FARO, originally developed for rockfall
barriers and afterwards calibrated for debris flow impacts, lead already to structural
improvements on barrier design. Decisive for the barrier design is the first dynamic impact
pressure depending on the flow velocity and afterwards the hydrostatic pressure of
the complete retained material behind the barrier. Therefore volume estimation
of open shallow landslides by assessing the thickness of the failure layer and the
width of the possible failure are essential for the required barrier design parameter
height and width. First results of the calculated drag coefficients of dynamic impact
pressure measurements showed that the dynamic coefficient cw is much lower than
1.0 which is contradictory to most of existing dimensioning property protection
guidelines.
It appears to us that special adaptation to the system like smaller mesh sizes and special
ground-barrier interface compared to normal rock-fall barriers and channelised debris
flow barriers are necessary to improve the retention behavior of shallow landslide
barriers.
Detailed analysis of the friction coefficient in relationship with pore water pressure
measurements gives interesting insights into the dynamic of fluid-solid mixed flows. Impact
pressures dependencies on flow features are analyzed and discussed with respect to existing
models and guidelines for shallow landslides. |
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