A user's approach to assess numerical codes for saturated and unsaturated seepage conditions

Chapuis, Robert P.; Chenaf, Djaouida; Bussière, Bruno; Aubertin, Michel; Crespo, Rodolfo

doi:10.1139/cgj-38-5-1113

Cited by 14 publications

(15 citation statements)

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“…Normally applied to lab-scale experiments in order to ensure physical realism and equivalency at larger scales (Kline 1965;Munson et al 1994), similitude can also be used when applying numerical models to difficult problems. Convergence and mass balance were verified for each simulation and the model-calculated hydraulic conductivities (based on the simulated pressures) were verified to be consistent with those entered into the model (following the approach of Chapuis et al 2001). Following the solution, the system was backscaled to return to the original conditions.…”

Section: Simulation Approachmentioning

confidence: 99%

Numerical Modelling of Flow and Capillary Barrier Effects in Unsaturated Waste Rock Piles

et al. 2005

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Flow systems in unsaturated waste rock piles were simulated using a two-dimensional numerical model (HYDRUS). The conceptual models are based on homogeneous (unstructured) waste piles, and on structured piles that include either horizontal or inclined fine-grained layers within a coarser host material, forming a capillary barrier system. The approach considers fully transient conditions and uses observed climatic data from a mine site in northern Quebec, Canada. All physical properties of the porous media, including the water retention curves, were obtained from measured data. Different geometric configurations were tested to determine their effect on moisture distribution and water flow, which ultimately control the potential for acid rock drainage (ARD). The simulations begin with a relatively dry initial condition under hydrostatic equilibrium. After an initial transient period, the simulated internal moisture distribution became periodic with a regular pattern of seasonal fluctuations. The simulations suggest that flow can be controlled in such systems using inclined fine-grained layers that retain and divert moisture due to capillary barrier effects. With horizontal layers, the local flow regimes become unstable, causing vertical preferential flow zones to develop below the barriers wherever the local water pressure first exceeds the entry pressure of the underlying coarser material. In this scenario, ARD production can remain high since a large fraction of the internal pile is being flushed. A shallow downward slope in the layers forces drainage toward the outer boundary and maintains lower saturation in the centre of the pile, thus potentially reducing the amount and mobility of ARD.

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Section: Simulation Approachmentioning

confidence: 99%

Numerical Modelling of Flow and Capillary Barrier Effects in Unsaturated Waste Rock Piles

et al. 2005

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“…With due consideration of saturated and unsaturated seepage, the numerical calculations provided a higher flow rate. Crespo (1994) 1.37 × 10 -3 m 3 /(min·m) using version 4 of the code with a finer grid of 1145 elements of 1.0 m. Furthermore, the numerical analysis gave a higher position for the water table (u w = 0) than the flow-net technique (Bowles 1984), and thus a larger seepage face (exit at 8.5 m instead of 6.5 m) along the downstream slope (Chapuis et al 2001).…”

Section: Geometry and Hydraulic Parametersmentioning

confidence: 99%

“…In the case of Seep/W, Chapuis et al (1993) published such an evaluation of the performance (for a previous version of Seep/W). Chapuis et al (2001) and Chenaf and Chapuis (1999) have provided recent evaluations of the numerical code, providing at the same time ways to handle convergence problems. Hence, the Seep/W software was deemed satisfactory to study the problems of interest here.…”

Section: Seep/w Softwarementioning

confidence: 99%

A simplified method to estimate saturated and unsaturated seepage through dikes under steady-state conditions

Chapuis¹,

Aubertin²

2001

Can. Geotech. J.

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The seepage rate through homogeneous or zoned dikes includes saturated and unsaturated flow. The latter is often neglected but should be considered to obtain the positions of the water table and the seepage face that may develop either on the downstream slope of a homogeneous dike or within the filter layer behind the core of a zoned dike. Different dikes with heights of 5, 10, 20, and 50 m have been analyzed numerically with a two-dimensional finite element code. The cases investigated include the most frequent types of small dikes designed to retain municipal or industrial wastewater. Solutions are proposed to solve numerically two difficulties related to the representation of saturated and unsaturated physical flow conditions. One difficulty is treating a downstream seepage face. The other is treating the passage of water from the core into a draining layer. The paper presents simple expressions to predict the total (saturated and unsaturated) seepage flow rate through a dike and discusses precautions to be taken.Résumé : Le débit de fuite des digues homogènes ou zonées inclut les écoulements saturés et non saturés. Ces derniers sont souvent négligés mais devraient être considérés pour avoir les positions de la nappe et de la surface de suintement qui peut se développer sur la pente aval d'une digue homogène ou dans le filtre à l'arrière du noyau d'une digue zonée. Différentes digues de hauteurs 5, 10, 20 et 50 m ont été analysées numériquement avec un code bidimensionnel d'éléments finis. Les cas étudiés comprennent les types les plus fréquents de petites digues conçues pour retenir des eaux usées municipales ou industrielles. On propose des solutions pour résoudre numériquement deux difficultés reliées à la représentation des conditions physiques d'écoulement saturé et non saturé. Une difficulté est le traitement d'une surface de suintement. L'autre est le traitement du passage de l'eau du noyau dans une couche drainante. L'article propose des expressions simples pour prédire le débit de fuite total (saturé et non saturé) à travers une digue et discute des précautions à prendre.

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“…This code was selected because it has passed several tests (Chapuis et al 2001) for steady-state and transient problems in either unsaturated or saturated materials, including equations of Theis, Thiem, and Dupuit. This code was selected because it has passed several tests (Chapuis et al 2001) for steady-state and transient problems in either unsaturated or saturated materials, including equations of Theis, Thiem, and Dupuit.…”

Section: Finite-element Verificationmentioning

confidence: 99%

Travel Time to a Well Pumping an Unconfined Aquifer without Recharge

Chapuis¹,

Chesnaux²

2006

Ground Water

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A solution is given for the travel time to a well pumping an ideal, horizontal unconfined aquifer, under steady-state conditions, when recharge from infiltration is negligible. Three forms of the solution are provided: a closed-form solution, an integral to be calculated in a worksheet, and a simple equation. The three forms of the solution give travel times nearly identical to those obtained using a finite-element code for saturated and unsaturated flow and particle tracking.

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A user's approach to assess numerical codes for saturated and unsaturated seepage conditions

Cited by 14 publications

References 0 publications

Numerical Modelling of Flow and Capillary Barrier Effects in Unsaturated Waste Rock Piles

Numerical Modelling of Flow and Capillary Barrier Effects in Unsaturated Waste Rock Piles

A simplified method to estimate saturated and unsaturated seepage through dikes under steady-state conditions

Travel Time to a Well Pumping an Unconfined Aquifer without Recharge

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