Critical hydraulic gradients for seepage-induced failure of landslide dams

Okeke, Austin Chukwueloka; Wang, Fawu

doi:10.1186/s40677-016-0043-z

Cited by 35 publications

(13 citation statements)

References 53 publications

(52 reference statements)

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“…pore water pressure at Pwp3. Stability and time of failure of dam crest decreases with increase in inflow rate into the reservoir (Okeke and Wang 2016a). Similarly decrease in inflow rate will increase the stability and failure time.…”

Section: Resultsmentioning

confidence: 98%

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The relationship among the premonitory factors of landslide dam failure caused by seepage: an experimental study

Dhungana

Wang

2019

Geoenviron Disasters

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Background: A landslide dam always has the potential for catastrophic failure with high risk for life, cost and, property damage at the downstream site. The formation of a landslide dam is a natural process; thus, minimizing the risk due to its failure is important. Landslide dam failure can be categorized into three types: seepage failure, overtopping and slope failure. As described by other researchers, the established premonitory factors of landslide dam failure are hydraulic gradients, seepage and turbidity as well as vertical displacement and inflow into the reservoir. Methodology: This study only considered seepage failure and used flume experiments to understand it. Three groups of samples which represented fine, medium and coarse particle sizes, respectively, were prepared by Silica sand S4, S5, S6 and S8 of different proportion. These samples were used to conduct the flume experiments of failure and not failure case. Result: For failure cases, it was found that GI samples have a higher hydraulic gradient and that the seepage water takes time to exit the dam body-however, the seepage water has more TSS. GII samples also had a higher hydraulic gradient, while the flow of seepage water was faster than that of the fine sample with a low TSS. For GIII samples, the hydraulic gradient was very low in comparison with the GI and GII samples. The GIII samples had TSS values that were quite a bit higher than those of the GII samples and lower than those of the GI samples. Experiments on GI samples failed at each attempt; however, the GI samples with kaolinite did not fail and had a higher TSS value. For a GII sample of a non-failed case, the hydraulic gradient was lower than for GI samples and the seepage water flow was faster but the vertical displacement was constant and TSS was on a decreasing order. For a GIII sample, the hydraulic gradient became constant after reaching its initial peak value and TSS was on a decreasing order with an initially increasing vertical displacement that would become constant. Conclusion: Seepage failure of a landslide dam can be predicted by understanding the nature of its premonitory factors. These factors behave differently in different particle size samples. The TSS trend line may be the initial factor for checking the stability of a dam crest. A landslide dam with an increasing TSS order will fail and a decreasing order may not fail. Based on all experiments, it can be concluded that the hydraulic gradient has three stages: 1) it starts to increase and reaches a peak value; 2) it starts to decrease from the peak value and reaches a minimum; and 3) it starts to increase again where the seepage water begins to come out and the vertical displacement starts to increase. Dam failures always occur when seepage water comes out with an increasing TSS and an increasing vertical displacement. Repeated experiments on samples having more fine particles show that if a landslide dam is formed by fine particles, then there would be a high chance of its failure. In case of a constant hydraulic ...

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Section: Resultsmentioning

confidence: 98%

“…The parameters related to seepage water can enlighten the failure process of a landslide dam. Darcy (1856, cited in Fredlund et al 2012 and Okeke and Wang (2016a) have noted that the seepage flow velocity into a dam is directly dependent upon the hydraulic gradient, as shown in Eq. 4:…”

Section: Introductionmentioning

confidence: 99%

The relationship among the premonitory factors of landslide dam failure caused by seepage: an experimental study

Dhungana

Wang

2019

Geoenviron Disasters

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“…Second, groundwater seepage caused by the drawdown of the reservoir water level decreased landslide stability. When the reservoir level drops rapidly, the dissipation of pore water pressure in the landslide body is slower than the decrease of external hydrostatic pressure [18,43,44]. The transient seepage induced by this lagging effect creates seepage force along the sliding direction [45], which increased the slip force and further reduced slope stability.…”

Section: Characterizing the Development Pattern Of The Landslidementioning

confidence: 99%

Characterizing the Development Pattern of a Colluvial Landslide Based on Long-Term Monitoring in the Three Gorges Reservoir

et al. 2021

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Since the impoundment of the Three Gorges Reservoir (TGR) in June 2003, the fluctuation of the reservoir water level coupled with rainfall has resulted in more than 2500 landslides in this region. Among these instability problems, most colluvial landslides exhibit slow-moving patterns and pose a significant threat to local people and channel navigation. Advanced monitoring techniques are therefore implemented to investigate landslide deformation and provide insights for the subsequent countermeasures. In this study, the development pattern of a large colluvial landslide, locally named the Ganjingzi landslide, is analyzed on the basis of long-term monitoring. To understand the kinematic characteristics of the landslide, an integrated analysis based on real-time and multi-source monitoring, including the global navigation satellite system (GNSS), crackmeters, inclinometers, and piezometers, was conducted. The results indicate that the Ganjingzi landslide exhibits a time-variable response to the reservoir water fluctuation and rainfall. According to the supplement of community-based monitoring, the evolution of the landslide consists of three stages, namely the stable stage before reservoir impoundment, the initial movement stage of retrogressive failure, and the shallow movement stage with stepwise acceleration. The latter two stages are sensitive to the drawdown of reservoir water level and rainfall infiltration, respectively. All of the monitoring approaches used in this study are significant for understanding the time-variable pattern of colluvial landslides and are essential for landslide mechanism analysis and early warning for risk mitigation.

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“…The soil parameters are also important for the critical gradients [7,21,22]. The effects of the void ratio e and the mean grain diameter d θk on the critical gradients are shown in Figure 9.…”

Section: Effects Of Other Parametersmentioning

confidence: 99%

“…This parameter is usually defined as the critical condition at which the effective stress of the soil becomes negligible [7]. Apparently, a large number of theoretical and experimental approaches have been used to obtain critical hydraulic gradients in water-retaining structures [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Model to Predict the Critical Hydraulic Gradient for Soil Particle Movement under Two-Dimensional Seepage Flow

Huang

Bai

et al. 2017

Water

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Abstract:The soil particle movement under seepage flow is one of the predominant mechanisms responsible for incidents and failures of dams and streambanks. However, little attention has been paid to the critical hydraulic gradient under two-dimensional (2-D) seepage flow. In this study, a theoretical model was established under 2-D seepage flow to predict the critical hydraulic gradients for soil particle movement. In this model, the sediment particle rolling theory was used, while taking into account the relative exposure degree of the soil grains and the seepage direction. The model was validated through qualitative analysis and comparison with previous data, and showed considerable superiority over Terzaghi's model. In addition, the effect of the soil internal instability, implying that the critical hydraulic gradient of unstable soil is lower than that of stable soil, was discussed. Various parameters of the model were also analyzed. The results showed that the seepage direction angle was positively related to the critical gradient, whereas the void and the mean diameter of the soil were negatively related to it. Finally, the model proposes a calculation method for the particle movement initiation probability, which is regarded as a key parameter in the sediment transport model.

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Critical hydraulic gradients for seepage-induced failure of landslide dams

Cited by 35 publications

References 53 publications

The relationship among the premonitory factors of landslide dam failure caused by seepage: an experimental study

The relationship among the premonitory factors of landslide dam failure caused by seepage: an experimental study

Characterizing the Development Pattern of a Colluvial Landslide Based on Long-Term Monitoring in the Three Gorges Reservoir

A Theoretical Model to Predict the Critical Hydraulic Gradient for Soil Particle Movement under Two-Dimensional Seepage Flow

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