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| Titel |
Rockslide deformation monitoring with fiber optic strain sensors |
| VerfasserIn |
J. R. Moore, V. Gischig, E. Button, S. Loew |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 10, no. 2 ; Nr. 10, no. 2 (2010-02-02), S.191-201 |
| Datensatznummer |
250007925
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| Publikation (Nr.) |
 copernicus.org/nhess-10-191-2010.pdf |
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| Zusammenfassung |
| With micro-strain resolution and the capability to sample at rates of 100 Hz
and higher, fiber optic (FO) strain sensors offer exciting new possibilities
for in-situ landslide monitoring. Here we describe a new FO monitoring system
based on long-gauge fiber Bragg grating sensors installed at the Randa
Rockslide Laboratory in southern Switzerland. The new FO monitoring system
can detect sub-micrometer scale deformations in both triggered-dynamic and
continuous measurements. Two types of sensors have been installed: (1) fully
embedded borehole sensors and (2) surface extensometers. Dynamic measurements
are triggered by sensor deformation and recorded at 100 Hz, while continuous
data are logged every 5 min. Deformation time series for all sensors show
displacements consistent with previous monitoring. Accelerated shortening
following installation of the borehole sensors is likely related to long-term
shrinkage of the grout. A number of transient signals have been observed,
which in some cases were large enough to trigger rapid sampling. The
combination of short- and long-term observation offers new insight into the
deformation process. Accelerated surface crack opening in spring is shown to
have a diurnal trend, which we attribute to the effect of snowmelt seeping
into the crack void space and freezing at night to generate pressure on the
crack walls. Controlled-source tests investigated the sensor response to
dynamic inputs, which compared an independent measure of ground motion
against the strain measured across a surface crack. Low frequency signals
were comparable but the FO record suffered from aliasing, where undersampling
of higher frequency signals generated spectral peaks not related to ground
motion. |
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