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| Titel |
Geotechnical and hydrological investigations into a landslide prone site at Rufiberg, Canton Schwyz, Switzerland |
| VerfasserIn |
Linda Seward, Cornelia Broennimann, Seraina Kauer, Manfred Staehli, Sarah M. Springman, Michael Plötze |
| 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 |
250048587
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| Zusammenfassung |
| Rufiberg (Canton Schwyz, Switzerland) is known to be prone to shallow landslide events.
Situated on the opposing slope to the 1806 Goldau rock avalanche, the underlying bedrock
includes dipping marls, sandstone and conglomerates from the Molasse deposits of the Alps,
with a 1-2m cover of topsoil.
The monitoring site at Rufiberg is a collaboration between groups working at WSL, ETH
Zürich, EPF Lausanne and University of Zürich. It aims to lead to a better understanding of
the hydrological, hydrogeological and geotechnical processes that interact at Rufiberg to
cause slope instabilities.
The site is situated on a slope of average 30- and was set up in 2009 in the form of a 40m x
60m fenced off field, at approximately 1200m asl. Hydrological surveying at Rufiberg began
in 2009 with the installation of 4 clusters of TDR sensors, tipping bucket gauges and
groundwater wells, in order to establish the behaviour of water flow through the soil. Six
boreholes (11 cm in diameter) were drilled in November 2010 to depths of 2.2-9.15 m, all
of which were instrumented subsequently with piezometers and water pressure
sensors.
Soil characterisation at the site has shown that the topsoil is 1-2m in depth, and has an Ah
(organic, OM) layer of approximately 20cm depth overlying an orange (CM) medium
plasticity clay rich soil, and a highly gleyed grey (CM) medium plasticity clay. Samples were
taken from a 1 m x 1 m trench dug in the centre of the monitoring site at intervals of every
40cm down to bedrock. Particle size distribution curves indicate a CM soil, with a 20-35%
clay content (the majority of the remaining soil is made up of silt sized grains in all cases),
and a PIasticity Index ranging from 15% (Liquid Limit (LL)= 38%, Plastic Limit (PL) =
23%) at the top of the profile to 26% (LL = 45%, PL = 20%) near the boundary with the
bedrock.
Mercury Intrusion Porosimetry (MIP) and X Ray Diffraction (XRD) analysis have given
indications of the microstructural and mineralogical state of the soil profile. MIP samples
have shown a wide range of pore size distribution, with a modal pore size of 700 nm at the
top of the soil profile, decreasing to 60 nm at a depth of 158 cm. XRD analysis has indicated
that the dominant (up to 20 wt%) clay phase present at Rufiberg is Smectite: a clay mineral
with high swelling potential.
Ongoing studies aim to understand the hydrological processes occurring at Rufiberg, along
with the interactions between the clay mineralogy, porosity and permeability and other
geotechnical parameters such as compressibility and strength. Geophysical techniques will
be used to give a greater understanding of the subsurface structure of the soil and
bedrock and how the state of the ground varies with infiltration, exfiltration and
drainage. |
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