Threshold of Slope Instability Induced by Rainfall and Lateral Flow

Chen, Hung-En; Tsai, Tsung Han; Yang, Jinn‐Chuang

doi:10.3390/w9090722

Cited by 13 publications

(14 citation statements)

References 30 publications

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“…(2) infiltration-strain behavior is considered, but the air pressure in the ground is assumed to be equal to the atmospheric pressure, based on the assumption that air flow in the ground is relatively free compared to water flow [18][19][20]; (3) the two-phase flow of water and air is applied, but the stress-strain behavior of the soil is ignored [21,22]; and (4) hysteretic wetting and drying states are not considered, affecting variably saturated hydrologic response and slope failure [20,[23][24][25].…”

Section: Of 21mentioning

confidence: 99%

Slope Stability Analysis of Unsaturated Soil Slopes Based on the Site-Specific Characteristics: A Case Study of Hwangryeong Mountain, Busan, Korea

2020

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Shallow slope failures occur almost every year during the rainy season. Continuous observation of the meteorological parameters and hydrological characteristics is required to more clearly understand the triggering mechanisms of shallow slope failure. In addition, influential factors, such as type of relative permeability models, air flow, and variation of hydraulic conductivity associated with stress–strain behavior of soil, have significant effects on the actual mechanism of rainfall infiltration. Real-time data including hourly rainfall and pore water pressure in response to rainfall was recorded by devices; then, the change in pore pressure from the devices was compared to the results from the infiltration analysis with applications of three relative permeability models, air flow, and the coupled hydro-mechanical analysis to examine an appropriate site-specific approach to a rainfall infiltration analysis. The infiltration and stability analyses based on the site-specific hydrologic characteristics were utilized to create maps of safety factors that depend on the cumulative rainfall. In regions vulnerable to landslides, rainfall forecast information and safety factor maps built by applying various rainfall scenarios can be useful in preparing countermeasures against disasters during the rainy season.

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Section: Of 21mentioning

confidence: 99%

Slope Stability Analysis of Unsaturated Soil Slopes Based on the Site-Specific Characteristics: A Case Study of Hwangryeong Mountain, Busan, Korea

2020

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“…The details of the algorithm of the 2D-SWE module can be found in [23], and details of the soil failure module can be found in [11] or [7]. An iterative procedure ( Figure 1) is adopted to solve Equations (1) to (12).…”

Section: Soil Failure Modulementioning

confidence: 99%

“…Tsai and Wang [10] demonstrated the effect of different patterns of rainfall on shallow landslides in unsaturated soils, stimulated by dissipation through matric suction. Chen et al [11] further explored the effects of rainfall duration, rainfall amount, and lateral flow-induced slope failures, using a vertical two-dimensional (2D) numerical landslide model. The relationships between rainfall infiltration and slope failures have been discussed extensively.Recently, some studies have connected landslides with runoff depth.…”

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confidence: 99%

Investigation of the Influence of Rainfall Runoff on Shallow Landslides in Unsaturated Soil Using a Mathematical Model

Chiu

Chen

Yeh

2019

Water

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Infiltration and groundwater have been widely considered as the main factors that cause shallow landslides; however, the effect of runoff has received less attention. In this study, an in-house physical-process-based shallow landslide model is developed to demonstrate the influence of runoff. The model is controlled by coupling the shallow water equation (dynamic) and Richards' equation. An infinite slope stability analysis is applied to evaluate the possibility of regional landslides. A real, small catchment topography is adopted as a demonstration example. The simulation illustrates the variations of runoff and the factor of safety (FS) during a storm. The results indicate that, after the surface becomes saturated, the FS may keep varying due to the increasing pressure head, which is caused by increasing surface water depth. This phenomenon most likely occurs downstream where the slopes easily accumulate water. The depth of the surface water may also be a factor of slope failure. Therefore, it is essential to increase the accuracy of calculating the runoff depth when assessing regional shallow landslides. stimulated by the rise of the groundwater table. Tsai and Wang [10] demonstrated the effect of different patterns of rainfall on shallow landslides in unsaturated soils, stimulated by dissipation through matric suction. Chen et al. [11] further explored the effects of rainfall duration, rainfall amount, and lateral flow-induced slope failures, using a vertical two-dimensional (2D) numerical landslide model. The relationships between rainfall infiltration and slope failures have been discussed extensively.Recently, some studies have connected landslides with runoff depth. For example, Chan et al.[12] combined a hydrological model and a landslide susceptibility model to establish a landslide analysis procedure. The results of their study indicated that the runoff flow depth may be selected as an analysis factor instead of the rainfall depth or maximum rainfall intensity. However, studies have seldom directly confirmed the physical mechanism of runoff on shallow landslides; although surface runoff is considered to increase the water pressure and affect the boundary conditions of infiltration, this behavior has not been demonstrated clearly.Furthermore, most landslide models were simplified for modeling the surface water flow. Some models focusing on the simulation of the infiltration mechanism did not consider the water depth [13,14]. Some assumed a kinematic or diffusion wave to model surface water flow [15][16][17]. However, ignoring the runoff or simplifying the momentum equations may fail to evaluate the effect of surface runoff. For the purpose of accurately evaluating the influence of runoff, dynamic equations may be more suitable.This study develops an in-house physical-process-based landslide model to observe the influence of runoff on shallow landslides in unsaturated soil. The model is governed by the coupling of the 2D shallow water equation (dynamic) and one-dimensional (1D) Richards' equation to simu...

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“…Rainfall-induced landslides have caused many human casualties and severe property damage worldwide [1,2]. The initiation of rainfall-induced landslides is affected by various factors, such as the material properties of soil, topographic features, geological and hydrological characteristics, slope surface cover, and vegetation [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…Although numerous empirically based approaches have been widely applied to large areas using simple methods, deterministic physics-based approaches are preferable for a better understanding of the mechanisms of shallow landslides [13]. Numerous physically based studies have investigated infiltration behavior during rainfall using various approaches: (1) Adopting assumptions for simplification to solve the differential equation of Richards [14] by applying a single-phase fluid (water) flow [3,10,15,16]; (2) assuming that the air pressure in the void spaces of an unsaturated soil slope is equal to the atmospheric pressure [9,17,18]; (3) applying a two-phase fluid (water and air) flow [19][20][21][22][23]; and (4) considering hydraulic hysteresis, including the effects of capillarity and/or air entrapment, reflecting different hydraulic states under wetting and drying conditions [24,25]. Such physically based numerical studies have mainly been applied at slope or watershed scales.…”

Section: Introductionmentioning

confidence: 99%

Effects of Two-Phase Flow of Water and Air on Shallow Slope Failures Induced by Rainfall: Insights from Slope Stability Assessment at a Regional Scale

Kang

Cho

Kim

et al. 2020

Water

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Over 160 shallow landslides resulted from heavy rainfall that occurred in 26–27 July 2011 at Umyeon Mountain, Seoul, South Korea. To accurately reflect the fluid flow mechanism in the void spaces of soils, we considered the two-phase flow of water and air for rainfall infiltration analysis using available historical rainfall data, topographic maps, and geotechnical/hydrological properties. Variations in pore water and air pressure from the infiltration analysis are used for slope stability assessment. By comparing the results from numerical models applying single- and two-phase flow models, we observed that air flow changes the rate of increase in pore water pressure, influencing the safety factor on slopes with a low infiltration capacity, where ponding is more likely to occur during heavy rainfall. Finally, several slope failure assessments were conducted to evaluate the usefulness of using the two-phase flow model in forecasting slope stability in conditions of increased rainfall sums. We observed that the two-phase flow model reduces the tendency of over-prediction compared to the single-phase model. The results from the two-phase flow model revealed good agreement with actual landslide events.

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Threshold of Slope Instability Induced by Rainfall and Lateral Flow

Cited by 13 publications

References 30 publications

Slope Stability Analysis of Unsaturated Soil Slopes Based on the Site-Specific Characteristics: A Case Study of Hwangryeong Mountain, Busan, Korea

Slope Stability Analysis of Unsaturated Soil Slopes Based on the Site-Specific Characteristics: A Case Study of Hwangryeong Mountain, Busan, Korea

Investigation of the Influence of Rainfall Runoff on Shallow Landslides in Unsaturated Soil Using a Mathematical Model

Effects of Two-Phase Flow of Water and Air on Shallow Slope Failures Induced by Rainfall: Insights from Slope Stability Assessment at a Regional Scale

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