Analysis of Slope Stability Considering the Saturation Depth Ratio by Rainfall Infiltration in Unsaturated Soil

Abstract. Most landslides in Korea are classified as shallow landslides with an average depth of less than 2 m. These shallow landslides are associated with the advance of a wetting front in the unsaturated soil due to rainfall infiltration, which results in an increase in water content and a reduction in the matric suction in the soil. Therefore, this study presents a modified equation of infinite slope stability analysis based on the concept of the saturation depth ratio to analyze the slope stability change associated with the rainfall on a slope. A rainfall infiltration test in unsaturated soil was performed using a column to develop an understanding of the effect of the saturation depth ratio following rainfall infiltration. The results indicated that the rainfall infiltration velocity due to the increase in rainfall in the soil layer was faster when the rainfall intensity increased. In addition, the rainfall infiltration velocity tends to decrease with increases in the unit weight of soil. The proposed model was applied to assess its feasibility and to develop a regional landslide susceptibility map using a Geographic Information System (GIS). For that purpose, the spatial databases for input parameters were constructed and landslide locations were obtained. In order to validate the proposed approach, the results of the proposed approach were compared with the landslide inventory using ROC (Receiver Operating Characteristics) graph. In addition, the results of the proposed approach were compared with the previous approach used steady state hydrological model. Consequently, the approach proposed in this study displayed satisfactory performance in classifying landslide susceptibility and showed better performance than the steady state approach.

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A method for predicting the factor of safety of an infinite slope based on the depth ratio of the wetting front induced by rainfall infiltration

Natural Hazards and Earth System Science ◽

10.5194/nhess-15-1835-2015 ◽

2015 ◽

Vol 15 (8) ◽

pp. 1835-1849 ◽

Cited By ~ 19

Author(s):

B.-G. Chae ◽

J.-H. Lee ◽

H.-J. Park ◽

J. Choi

Keyword(s):

Steady State ◽

Slope Stability ◽

Unsaturated Soil ◽

Landslide Susceptibility ◽

Shallow Landslides ◽

Rainfall Infiltration ◽

Wetting Front ◽

Operating Characteristics ◽

Infinite Slope ◽

Depth Ratio

Abstract. Most landslides in Korea are classified as shallow landslides with an average depth of less than 2 m. These shallow landslides are associated with the advance of a wetting front in the unsaturated soil due to rainfall infiltration, which results in an increase in water content and a reduction in the matric suction in the soil. Therefore, this study presents a modified equation of infinite slope stability analysis based on the concept of the saturation depth ratio to analyze the slope stability change associated with the rainfall on a slope. A rainfall infiltration test in unsaturated soil was performed using a column to develop an understanding of the effect of the saturation depth ratio following rainfall infiltration. The results indicated that the rainfall infiltration velocity due to the increase in rainfall in the soil layer was faster when the rainfall intensity increased. In addition, the rainfall infiltration velocity tends to decrease with increases in the unit weight of soil. The proposed model was applied to assess its feasibility and to develop a regional landslide susceptibility map using a geographic information system (GIS). For that purpose, spatial databases for input parameters were constructed and landslide locations were obtained. In order to validate the proposed approach, the results of the proposed approach were compared with the landslide inventory using a ROC (receiver operating characteristics) graph. In addition, the results of the proposed approach were compared with the previous approach used: a steady-state hydrological model. Consequently, the approach proposed in this study displayed satisfactory performance in classifying landslide susceptibility and showed better performance than the steady-state approach.

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Effects of Airflow Induced by Rainfall Infiltration on Unsaturated Soil Slope Stability

Transport in Porous Media ◽

10.1007/s11242-015-0469-x ◽

2015 ◽

Vol 107 (3) ◽

pp. 821-841 ◽

Cited By ~ 21

Author(s):

Dong-mei Sun ◽

Yong-ge Zang ◽

Stephan Semprich

Keyword(s):

Slope Stability ◽

Unsaturated Soil ◽

Rainfall Infiltration ◽

Soil Slope

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A Non-Linear, Time-Variant Approach to Simulate the Rainfall-Induced Slope Failure of an Unsaturated Soil Slope: A Case Study in Sapa, Vietnam

Journal of Disaster Research ◽

10.20965/jdr.2021.p0512 ◽

2021 ◽

Vol 16 (4) ◽

pp. 512-520

Author(s):

The Viet Tran ◽

Hoang Viet Hung ◽

Huy Dung Pham ◽

Go Sato ◽

Hoang Hiep Vu ◽

...

Keyword(s):

Stability Analysis ◽

Slope Stability ◽

Unsaturated Soil ◽

Slope Failure ◽

The United States ◽

Slope Stability Analysis ◽

Rainfall Infiltration ◽

Landslide Event ◽

Non Linear ◽

The Stability

In this study, the Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis (TRIGRS), v2.1 program, and module SLOPE/W in the Geostudio package were adopted for assessing rainfall-induced slope failure. TRIGRS was developed by the United States Geological Survey to determine the time-varying groundwater table at the regional scale under rainfall infiltration. The program employs partial differential equations represented by one-dimensional vertical flow in homogeneous materials for unsaturated conditions. With the application of a simple runoff routing scheme combined with the mass balance between rainfall, infiltration, and runoff over the study area, the distribution of the transient pore-water pressures within the entire landscape was simulated considering both the surface and subsurface flow. Additionally, compared to the traditional two-dimensional approach, the topographical conditions were also considered during the groundwater simulation. For conducting the slope stability analysis, a typical cross-section was constructed based on the site description. The predicted water-tables at the observed time of failure of the typical section were extracted and used in SLOPE/W to conduct the time-dependent modelling of rainfall-induced slope failures. In this study, the non-linear method was employed for simulating unsaturated soil shear strength, and the stability of the slope was evaluated using Bishop’s simplified method. We applied the approach to the landslide event that occurred on August 5, 2019, in Sapa district, Lao Cai province, Vietnam. The event resulted in severe damage and blocked the road for days. The predicted results on the stability of the slope as the factor of safety were compared with the actual slope failure during the event. The results showed that, by inputting accurate data, the applied approach could provide valuable evidence about the time of the slope failure.

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Soil Strength Reduction Method Induced by Variation of Water Content

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.847 ◽

2012 ◽

Vol 170-173 ◽

pp. 847-852

Author(s):

Peng Ming Jiang ◽

Zhong Lei Yan ◽

Peng Li

Keyword(s):

Slope Stability ◽

Unsaturated Soil ◽

Unsaturated Soils ◽

Characteristic Curve ◽

Strength Reduction ◽

Actual State ◽

Soil Slope ◽

Simple Method ◽

The Common ◽

The Stability

As the complexity of unsaturated soil theory, and it must have a long test period when we study the unsaturated soils, so the conventional design analysis software does not provide such analysis, so we can imagine that such a slope stability analysis does not accurately reflect the actual state of the slope. Based on the known soil moisture content，this paper use the soil water characteristic curve and strength theory of unsaturated soil to calculate the strength reduction parameters of soil which can calculate the stability of the soil slope when using the common calculation method. It is noticeable that this method can be extended and applied if we establish regional databases for this simple method, and these databases can improve the accuracy of the calculation of slope stability.

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