A force transfer mechanism for triggering landslides during rainfall infiltration

Liu, Gang; Tong, Fuguo; Zhao, Yitong; Tian, Bo

doi:10.1007/s11629-018-5043-x

Cited by 18 publications

(21 citation statements)

References 30 publications

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“…After 12 h, the infiltration rates increased sharply in the single-phase flow model during heavy rainfall whereas those from the two-phase flow model increased relatively gradually during this period. This is because air pressure interrupted the water flow into the void spaces and was accompanied by ponding ( [20,35,56]). This shows clearly that air pressure impacts the infiltration rate particularly in the low permeable soils where ponding effects occur frequently.…”

Section: Validation With Comparison To Field Measurementsmentioning

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%

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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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Section: Validation With Comparison To Field Measurementsmentioning

confidence: 99%

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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“…The third factor to consider is the entrapped air. Previous reports have noted that entrapped air in the soil layer can increase the pore water pressure [16][17][18][19][20][21]. As Yamasaki et al [16] noted, soil pipes usually contain relatively large voids.…”

Section: Introductionmentioning

confidence: 98%

“…They also indicated that the soil pipe flow occurs only when soil air can escape freely from the soil pipe to the atmosphere, and air entrapment in the soil pipes may be affected by soil water and air flow in the soil matrix around the soil pipe. Moreover, several researchers argued about the effects of entrapped air in the soil layer on hydrological processes (e.g., [16][17][18][19][20][21]). These studies revealed that the entrapped air contributed rapid increase of pore water pressure and enhanced hillslope discharge through field observation and laboratory experiments.…”

Section: Introductionmentioning

confidence: 99%

“…So, it has been considered that the entrapped pore air in the soil layer could induce slope instability, because of a quick and large groundwater table increase [19][20][21]. For example, Liu et al [21] pointed that pore air pressure by rainfall infiltration can increase sharply at difference locations and that the pore air pressure can also cause a rapid decrease in the slope safety factor by numerical simulation. They also indicated that pore air pressure throughout the whole unsaturated zone has the same value, which means that the air pressure could spread quickly to the whole sample by laboratory experiment.…”

Section: Introductionmentioning

confidence: 99%

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Bench-Scale Experiments on Effects of Pipe Flow and Entrapped Air in Soil Layer on Hillslope Landslides

et al. 2019

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Soil pipes are commonly found in landslide scarps, and it has been suggested that build-up of pore water pressure due to clogged soil pipes influences landslide initiation. Several researchers have also suggested that entrapped air in the soil layer increases the pore water pressure. We carried out bench-scale model experiments to investigate the influence of soil pipes and entrapped air on the build-up of pore water pressure. We installed a water supply system consisting of an artificial rainfall simulator, and used a water supply tank to supply water to the model slope and artificial pipe. We used two types of artificial pipe: A straight pipe, and a confluence of three pipes. Furthermore, we placed a layer of silica sand on top of the model slope to investigate the effect of entrapped air in the soil layer on the build-up of pore water pressure. Silica sand is finer than the sand that we used for the bulk of the model slope. Our results indicate that, although artificial pipes decrease the pore water pressure when the amount of water supplied was smaller than the pipe drainage capacity, the pore water pressure increased when the water supply was too large for the artificial pipe to drain. In particular, the confluence of pipes increased the pore water pressure because the water supply exceeded the drainage capacity. The results also indicate that entrapped air increases the pore water pressure in the area with relatively low drainage capacity, too. Based on these results, we found that although soil pipes can drain a certain amount of water from a soil layer, they can also increase the pore water pressure, and destabilize slopes. Furthermore, entrapped air enhances the trend that the pore water pressure can increase in the area with relatively low drainage capacity, as pore water pressure increases when too much water is supplied, and the artificial pipe cannot drain all of it.

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A finite element model for simulating surface run‐off and unsaturated seepage flow in the shallow subsurface

Liu

Tong

Tian

2019

Hydrological Processes

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This work introduces water-air two-phase flow into integrated surface-subsurface flow by simulating rainfall infiltration and run-off production on a soil slope with the finite element method. The numerical model is formulated by partial differential equations for hydrostatic shallow flow and water-air two-phase flow in the shallow subsurface. Finite element computing formats and solution strategies are presented to obtain a numerical solution for the coupled model. An unsaturated seepage flow process is first simulated by water-air two-phase flow under the atmospheric pressure boundary condition to obtain the rainfall infiltration rate. Then, the rainfall infiltration rate is used as an input parameter to solve the surface run-off equations and determine the value of the surface run-off depth. In the next iteration, the pressure boundary condition of unsaturated seepage flow is adjusted by the surface run-off depth. The coupling process is achieved by updating the rainfall infiltration rate and surface run-off depth sequentially until the convergence criteria are reached in a time step. A well-conducted surface run-off experiment and traditional surface-subsurface model are used to validate the new model. Comparisons with the traditional surface-subsurface model show that the initiation time of surface run-off calculated by the proposed model is earlier and that the water depth is larger, thus providing values that are closer to the experimental results. K E Y W O R D S integrated surface-subsurface flow modeling, rainfall infiltration, surface run-off, water-air two-phase flow

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A force transfer mechanism for triggering landslides during rainfall infiltration

Cited by 18 publications

References 30 publications

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

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

Bench-Scale Experiments on Effects of Pipe Flow and Entrapped Air in Soil Layer on Hillslope Landslides

A finite element model for simulating surface run‐off and unsaturated seepage flow in the shallow subsurface

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