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| Titel |
Incorporating an electro-magnetic view into a hydrological study on shallow landslide prediction - Laboratory experiments focused on soil displacement and subsequent shallow landslide initiation induced by rainfalls - |
| VerfasserIn |
T. Terajima, H. Miyajima, K. Hattori, H. Kohno, H. Ochiai, Y. Okada, I. Uchida |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020551
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| Zusammenfassung |
| Understanding the mechanism of precursors related to shallow landslides, such as small soil
displacement occurring commonly prior to shallow landslide initiation, must be
useful to advance a predictive accuracy of shallow landslide initiation and mitigate
subsequent sediment disasters. The small soil displacement, so called soil creep which is
well-known empirically as an indication of shallow landslide initiation, was focused on
understanding the effect of subsurface hydrology on soil displacement and shallow landslide
initiation. Soil displacement, pore water pressures, and self potential, which occurred
prior to shallow landslides, were measured in two flume experiments consisted of
an artificial sandy slope of 9 m long, 1 m wide, 0.7 m deep, and the slope of 32
degrees with the rainfall intensities of 100 and 80 mm/h. Following 4 findings were
obtained.
In subsurface hydrology:
#1) the direction of subsurface flow in the deep part of landslide masses began to change
parallel to the slope at around 30 min before the shallow landslide initiation. This timing
almost coincided with the start of the soil displacement;
#2) Stress paths with an increase in the soil weight by rainfall infiltration did not exceed
failure envelopes which were obtained from simple shear tests under saturated and
un-drainage conditions.
#3) In contrast, adding seepage force of subsurface flow to the normal and shear
stresses in the landslide masses made the stress paths be possible to exceed the failure
envelopes.
These things signify that the soil displacement and shallow landslides could not be
induced by the weight change in the soil accompanied with rainfall infiltration. Therefore, the
seepage force controlled by the changes in the direction and magnitude of subsurface flow
provided the changes in the normal and shear stresses of the soils, and must have been one of
the main causes of the soil displacement and shallow landslide initiation in the
experiments.
In the electro-magnetic view:
#4) The change in the self potential in the slopes showed similarity to behavior of the soil
and subsurface flow, representing that the change in the self potential coincided well with the
shallow landslide mechanism described above.
This indicates that observations of self potential must develop both a predictive
technology on the timing of shallow landslide initiation and some preventive measures on
sediment disasters around hill slopes.
Key word: Shallow landslide, Soil displacement, Seepage force, Subsurface hydrology,
Flow direction |
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