Capillary barrier effects in unsaturated layered soils, with special reference to the pyroclastic veneer of the Pizzo d’Alvano, Campania, Italy

2012 ◽  
Vol 71 (4) ◽  
pp. 791-801 ◽  
Author(s):  
D. Mancarella ◽  
V. Simeone
Keyword(s):  
Special Reference ◽  
Layered Soils ◽  
Capillary Barrier ◽  
Barrier Effects

Preliminary geotechnical assessment of the potential use of mixtures of soil and acid mine drainage neutralization sludge as materials for the moisture retention layer of covers with capillary barrier effects

2016 ◽  
Vol 53 (5) ◽  
pp. 828-838 ◽  
Author(s):  
Mamert Mbonimpa ◽  
Médard Bouda ◽  
Isabelle Demers ◽  
Mostafa Benzaazoua ◽  
Denis Bois ◽  
...  
Keyword(s):  
Acid Mine Drainage ◽  
Mine Drainage ◽  
Capillary Barrier ◽  
Moisture Retention ◽  
Mine Site ◽  
Barrier Effects ◽  
Acid Mine ◽  
Geotechnical Assessment ◽  
Site Rehabilitation ◽  
Water Contents

Lime treatment of acid mine drainage (AMD) generates sludge that is commonly stored in ponds for dewatering. The use of soil-aged sludge-based mixtures for mine site rehabilitation can allow the emptying of existing basins, thus extending their storage capacity, reducing the volume of the borrow soil pit required for mine site rehabilitation, and consequently reducing the mine footprint. The authors investigated the geotechnical properties of silty soil–sludge mixtures (SSMs) as possible components of covers with capillary barrier effects (CCBEs) to prevent AMD generation from mine waste. SSMs with β values of 10%, 15%, 20%, and 25% sludge (β = wet sludge mass / wet soil mass) were studied. Two water contents were considered for each of the mixture components: 175% and 200% for the sludge and 7.5% and 12.5% for the soil. Results indicate that saturated hydraulic conductivity (ksat) values were in the range of 10−5 cm/s for the soil and SSMs at void ratios ranging from 0.28 to 0.53, with values decreasing slightly when β was increased from 0% to 25%. The air-entry value (AEV) increased from 20 kPa for the soil alone to 35 kPa for the SSM with β = 25%. These values of ksat and AEV are comparable to those of materials used in the moisture retention layers of existing efficient CCBEs. However, the volumetric shrinkage increased from about 2% for the soil alone to values ranging between 24% and 32% for the SSM with β = 25%, depending on the initial water contents of the components. Tools are provided to estimate to which extent the use of sludge in SSMs can reduce the volume of borrow natural soil required for a moisture retention layer of a CCBE.

scholarly journals Oxygen migration through a cover with capillary barrier effects colonized by roots

2020 ◽  
Vol 57 (12) ◽  
pp. 1903-1914 ◽  
Author(s):  
Alex Proteau ◽  
Marie Guittonny ◽  
Bruno Bussière ◽  
Abdelkabir Maqsoud
Keyword(s):  
Oxygen Consumption ◽  
Root Colonization ◽  
Mine Drainage ◽  
Root Length Density ◽  
Mixed Forest ◽  
Capillary Barrier ◽  
Barrier Effects ◽  
Lower Oxygen ◽  
Oxygen Migration ◽  
Reactivity Coefficient

Covers with capillary barrier effects (CCBEs) are multi-layered oxygen barrier covers used in humid climates to reclaim reactive mine tailings and limit the generation of acid mine drainage. Once constructed, CCBEs are colonized by surrounding plants. Roots modify water storage and respire oxygen. The performance of CCBEs could evolve over time due to root colonization. Twenty-five plots with varying vegetation were investigated at a 17-year-old CCBE in the mixed forest of Quebec, Canada. Geotechnical parameters and root colonization of the moisture-retaining layer (MRL) of the CCBE were characterized. The performance of the MRL to control oxygen migration was assessed using oxygen consumption tests and numerical modeling. Despite root colonization at the surface of the MRL, oxygen fluxes generally complied with the CCBE’s design criteria. Root presence created oxygen consumption in the MRL, which could be expressed with a reactivity coefficient (Kr). A positive correlation (R2 = 0.65) was found between root length density and Kr. Oxygen consumption by root respiration helped to lower oxygen fluxes by 0.5 to 76 g/m2/year, with a mean of 13 g/m2/year. These results will help to better understand the influence of roots on CCBEs’ performance to control oxygen migration.

Analyses of water diversion along inclined covers with capillary barrier effects

2009 ◽  
Vol 46 (10) ◽  
pp. 1146-1164 ◽  
Author(s):  
M. Aubertin ◽  
E. Cifuentes ◽  
S. A. Apithy ◽  
B. Bussière ◽  
J. Molson ◽  
...  
Keyword(s):  
Climatic Conditions ◽  
Water Infiltration ◽  
Water Diversion ◽  
Key Factors ◽  
Capillary Barrier ◽  
Fine Grained ◽  
Barrier Effects ◽  
Fine Grained Soil ◽  
Cover Systems ◽  
Recharge Rates

Various types of cover systems can be used to control water infiltration into waste disposal sites. One promising option is to combine different types of soil to create a layered cover with capillary barrier effects (CCBE). A CCBE basically involves the placement of a relatively fine-grained soil, which acts as a water-retention layer, over a coarser capillary break material. On slopes, a CCBE promotes lateral water diversion. Inclined CCBEs, however, are relatively complex, as their behaviour is influenced by numerous factors. In this paper, the authors present the key results obtained from a numerical investigation into the response of steeply inclined CCBEs. The study evaluates the behaviour of covers under dry and humid climatic conditions. After a review of the physical processes and background studies, the paper presents simulation results that demonstrate the effect of key factors on the diversion length of covers, including layer thicknesses, material properties, and recharge rates. The results shown here indicate that increasing the thickness of the cover may improve its efficiency, but only up to a certain maximum beyond which the gain becomes minimal. These results should be of help to those involved in the design of inclined CCBEs.

Covers with Capillary Barrier Effects

2020 ◽  
pp. 167-186
Author(s):  
Isabelle Demers ◽  
Thomas Pabst
Keyword(s):  
Capillary Barrier ◽  
Barrier Effects

Field experimental cells to evaluate the hydrogeological behaviour of oxygen barriers made of silty materials

2007 ◽  
Vol 44 (3) ◽  
pp. 245-265 ◽  
Author(s):  
Bruno Bussière ◽  
Michel Aubertin ◽  
Mamert Mbonimpa ◽  
John W Molson ◽  
Robert P Chapuis
Keyword(s):  
Acid Mine Drainage ◽  
Unsaturated Flow ◽  
Mine Drainage ◽  
In Situ Monitoring ◽  
Oxygen Flux ◽  
Capillary Barrier ◽  
Barrier Effects ◽  
Acid Mine ◽  
Hydrogeological Behaviour

An in situ study was initiated to evaluate the efficiency of silts as moisture-retaining material in covers with capillary barrier effects (CCBEs) that aim at controlling the production of acid mine drainage (AMD). This investigation included the construction of four experimental cells covered by different layered cover configurations. Each CCBE was instrumented to monitor its hydrogeological behaviour. The degree of saturation (Sr) in the moisture-retaining (silty) materials was usually maintained above 85%, while Sr in the two sand layers placed above and below the silts was generally lower than 30%–50% (typical hydrogeological behaviour of efficient CCBEs). Suction measurements in the different layers of the four CCBEs were consistent with the observed Sr measurements during the four years of monitoring. The suctions measured in the moisture-retaining materials were lower than their respective air-entry values (AEV), while suctions largely exceeded the AEV of the sand in the capillary break layers. The oxygen flux calculations confirm that in each of the four CCBEs the flux through the CCBEs remained low for the entire duration of the experiment, hence limiting the generation of AMD. This study also confirmed the ability of silty materials to act as moisture retaining in a CCBE. Key words: cover with capillary barrier effects, acid mine drainage, experimental cells, in situ monitoring, unsaturated flow, diffusion, oxygen flux.

Diffusion and consumption of oxygen in unsaturated cover materials

2003 ◽  
Vol 40 (5) ◽  
pp. 916-932 ◽  
Author(s):  
M Mbonimpa ◽  
M Aubertin ◽  
M Aachib ◽  
B Bussière
Keyword(s):  
Analytical Solutions ◽  
Unsaturated Soils ◽  
Numerical Solutions ◽  
Mine Drainage ◽  
Effective Diffusion ◽  
Oxygen Flux ◽  
Capillary Barrier ◽  
Gas Exchanges ◽  
Barrier Effects ◽  
Two Parameters

Covers installed over waste disposal sites are used to control water and gas exchanges with the surrounding environment. One example involves covers built to limit oxygen flux to sulphidic mining and milling wastes, which can be the source of acidic leachate. In this paper, the authors present an approach to evaluate oxygen flux and its controlling parameters, the effective diffusion coefficient De and reaction (consumption) rate coefficient Kr. A laboratory experimental procedure to determine these two parameters simultaneously is described, and the proposed interpretation method is presented with a few sample results. New analytical solutions are developed to calculate oxygen flux through covers with capillary barrier effects (CCBE). The proposed solutions are compared with results ensuing from a numerical treatment of Fick's laws. Specific applications of these analytical solutions are presented and discussed.Key words: unsaturated soils, covers, capillary barrier, Fick's laws, oxygen diffusion, acid mine drainage, analytical solutions, numerical solutions.

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