Assessment of exit hydraulic gradients at the toe of levees in water drawdown conditions

López-Acosta, Norma Patricia; Sánchez, Marcelo; Auvinet, G.; Pereira, Jean‐Michel

doi:10.1201/b17703-21

Cited by 5 publications

(3 citation statements)

References 3 publications

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“…A second mechanism may be observed when high-hydraulic conductivity soils on the landside of the levee are overlain by a soil layer having lower hydraulic conductivity (Rice et al, 2012). Assesment of exit hydraulic gradients at the toe of levees in water drawdown conditions (López et al, 2015). Due to the lower hydraulic conductivity, water pressure is created at the base of the top layer.…”

Section: Safety Factorsmentioning

confidence: 99%

Numerical Modelling Of Flood Induced Seepage Under Levees

Semerci¹,

Tayfur²,

Pulat³

2021

European Journal of Science and Technology

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Flood creates the most complex problems of engineering hydrology and extreme flood contains the crucial risk for urban areas, infrastructure, industry and agriculture. The aim of this paper is to study the transient flow caused by flood for levee of Filyos River. Numerical modeling based on finite element method was performed in the analyses. PlaxFlow which is an add-on module to Plaxis 2D, is used for the time variation of seepage in several points of interest within the levee. Exit velocity at several points of interest within the levee and degree of saturation of levee and hydraulic gradient were investigated. In addition, under seepage of water through different soil types underneath Filyos levee was examined. The results of transient flow analyses when piping occurred and sand boil formed were presented for different soil types.

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Section: Safety Factorsmentioning

confidence: 99%

Numerical Modelling Of Flood Induced Seepage Under Levees

Semerci¹,

Tayfur²,

Pulat³

2021

European Journal of Science and Technology

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“…These factors reduce retaining loads and, therefore, the slope stability [3][4]. The reservoir drawdown leads to increased filtration gradients, which may cause filtration deformations in the soil mass or on the slope surface [5]. Hydrotechnical practice shows multiple cases of accidents related with water level drop in the reservoir [6][7].…”

Section: Introductionmentioning

confidence: 99%

“…Ψ In 1980, Van Genuchten [20] used the Mualem method to propose a model for describing the hydrophysical properties of soils using the expressions of the Mualem-Van Genuchten model. This model is widely used in practice in numerical modeling of filtration processes [5][6].…”

Section: Introductionmentioning

confidence: 99%

Change in filtration gradients during head water drawdown

Aniskin,

Stupivtsev

2023

E3S Web Conf.

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Changes in the water level in a reservoir lead to changes of filtration stream parameters in the soil structure. The position of the depression curve, value and direction of filtration gradients and speeds changes near the slope of the structure. Operation practice of waterworks in such conditions shows that emergencies are possible. Changes in filtration stream parameters can cause filtration deformations of soils and loss of slope stability of a soil dam. The article considers unsteady filtration in a homogeneous soil dam for five options of composing soils having various filtration coefficients. The reservoir drawdown rate is considered as an affecting factor. Using the numeric finite-element method and PLAXIS 2D software suite, filtration stream parameters were found for the considered options. Maximum filtration gradients near the upstream slope of the soil dam were found for various options of dam soil permeability and drawdown rate. As the reservoir draws down, directions and filtration gradients and rates change near the slope surface. Maximum gradients occur at various stages of drawdown depending on its speed and reservoir soil permeability. Maximum gradients are quite high, which shows the need for anti-filtration measures.

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Influence of factors on filtration regime of an earth dam under headwater drawdown

Aniskin

Stupivtsev

2023

Vestnik MGSU

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Introduction. As the statistics of observations of groundwater retaining structures shows, one of the most significant factors of emergencies in these structures is the occurrence of filtration deformations in the dam body. This often results in the appearance of moves of concentrated filtration. The occurrence of these phenomena can be provoked by a rapid decrease of the headwater level known as reservoir drawdown. It can be caused either by the technological requirements of the operation of the hydraulic unit or by the occurrence of an emergency situation. Modern design standards require mandatory consideration of the case of rapid drawdown with an assessment of the filtration regime and stability of the structure. Materials and methods. The results of numerical studies of unsteady filtration in a homogeneous earth dam under reservoir drawdown are considered. Numerical studies were carried out on the basis of the finite element method using the PRAXIS software package. Test calculations were carried out, which showed the reliability of the results obtained. The influence of the soil filtration coefficient of the dam, the rate of drawdown and the slope of the structure on the change in the position of the depression curve and the value of the maximum pressure gradient is analyzed. Results. For the considered variants of earth dams with different characteristics, the parameters of the filtration flow are obtained when the headwater level changes: the position of the depression curve and the values of the maximum pressure gradients. An assessment of the possibility of occurrence of filtration deformations of soils of the upper prism of the dam is given. Conclusions. The use of the PLAXIS software package for solving problems of unsteady filtration under reservoir level changes allows to obtain reliable results that are well comparable with the results of other proven methods. At certain rates of runoff for soils of different permeability in the upper prism of an earth dam, large values of pressure gradients exceeding critical values may occur. This indicates the necessity to control the process of drawdown and the use of antifiltration measures.

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Assessment of exit hydraulic gradients at the toe of levees in water drawdown conditions

Cited by 5 publications

References 3 publications

Numerical Modelling Of Flood Induced Seepage Under Levees

Numerical Modelling Of Flood Induced Seepage Under Levees

Change in filtration gradients during head water drawdown

Influence of factors on filtration regime of an earth dam under headwater drawdown

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