Effect of the soil water characteristic curve on the stability of partially saturated slopes
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Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
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Rainfall significantly contributes to slope failure in unsaturated slopes by causing
a reduction in matrix suction and subsequent decline in shear strength of the soil.
Understanding the relationship between matrix suction and moisture content is crucial for describing the hydraulic behavior of unsaturated soil, typically represented
by the Soil-Water Characteristic Curve (SWCC). This study focuses on assessing
how SWCC affects the stability of partially saturated soil during infiltration us ing fully coupled-flow deformation analysis in PLAXIS 2D. To enhance efficiency
and automate analyses for numerous iterations, PLAXIS-remote scripting is utilized.Parameters that quantify the SWCC are utilized to depict the properties of
unsaturated soils. The Van- Genuchten parameters, which describe the hydraulic
behavior of unsaturated soil, have been determined based on the SWCC. Furthermore, the impact of Van Genuchten parameters (ga , gn) that best fit the SWCC on
the stability of unsaturated soil under rainfall conditions has been studied. The slope
stability under infiltration is initially examined based on the derived VG parameters. Subsequently, the impact of VG parameters on the stability of unsaturated
slopes is assessed by determining five different values for each parameter:ga and
gn. These values are utilized to generate five unique sets of VG parameters, resulting in 25 combinations. The stability of the unsaturated slope under the effect of
rainfall is then evaluated for these 25 combinations of VG parameters. In addition
to hydraulic parameters, factors such as the geometry of the slope and the shear
strength properties of the soil also play a significant role in influencing the stability
of unsaturated slopes. Therefore, a sensitivity analysis is conducted by varying the
slope geometry and shear strength properties to explore the impact of 25 different
combinations of Van Genuchten parameters. The resulting values of FOS are then
compared with the original slope geometry and shear strength properties for all 25
combinations of Van Genuchten parameters under the effect of rainfall, in order to
investigate the slope stability.Upon increasing the values of ga and gn, the FOS of
the slope significantly decreases under the influence of rainfall. Moreover, sensitivity
analysis results indicate that the stability of an unsaturated slope under consistent
rainfall infiltration is directly correlated with the VG parameters and shear strength
parameters, while being inversely proportional to the slope’s geometry.
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Ämne/nyckelord
Unsaturated Slope, SWCC, matrix suction, fully coupled flow-deformation analysis, FOS, PLAXIS 2D, remote scripting, python codes