Monitored and simulated variations in matric suction during rainfall in a residual soil slope |
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Authors: | Aurelian C Trandafir Roy C Sidle Takashi Gomi Toshitaka Kamai |
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Institution: | (1) Department of Geology and Geophysics, University of Utah, 135 South 1460 East Rm 717, Salt Lake City, UT 84112-0111, USA;(2) Slope Conservation Section, Geohazards Division, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, 611-0011 Kyoto, Japan;(3) Japan Science and Technology Agency, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, 611-0011 Kyoto, Japan;(4) Research Centre on Landslides, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, 611-0011 Kyoto, Japan |
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Abstract: | This research combines field, laboratory and numerical investigations to estimate the development of a wetting front within
a 1.2 m residual soil mantle on a steep forested slope during rainfall events. The field-monitored variations in matric suction
due to rain-water infiltration during various events revealed that the maximum infiltration rate was much higher when the
wetting front resided in the upper 20 cm of soil compared to the case when the wetting front advanced to depths > 20 cm. Laboratory
investigations on soil hydraulic properties (i.e., soil water characteristic curve, and hydraulic conductivity) were useful
to establish the parameters of a multilayer finite-element model for one-dimensional vertical infiltration. These parameters
were subsequently calibrated by matching the predicted and field measured transient pore water pressure responses during actual
rainstorms with irregular rainfall patterns. The calibrated simulation model was used to assess the migration of the wetting
front under uniform rainfall with different intensities. Based on the numerical results, a hyperbolic equation was developed
to predict the duration of uniform rainfall required for the propagation of wetting front to a certain depth for a given rainfall
intensity. The proposed equation was subsequently tested against field-monitored advancements of the wetting front during
real rainstorms with variable rainfall intensity. |
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Keywords: | Rainfall infiltration Matric suction Wetting front Residual soil slope Field measurements Numerical simulation |
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