Improved isolation of cadmium from paddy soil by novel technology based on pore water drainage with graphite-contained electro-kinetic geosynthetics

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tan ϕ, where ϕ is the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such as h(x) = 3x1/2 (m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well below h(x) = 3x1/2.

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Effect of drainage and sequential filling on the behavior of backfill in mine stopes

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0462 ◽

2014 ◽

Vol 51 (1) ◽

pp. 1-15 ◽

Cited By ~ 40

Author(s):

Nawfal El Mkadmi ◽

Michel Aubertin ◽

Li Li

Keyword(s):

Pore Water ◽

Numerical Study ◽

Water Drainage ◽

Filling Rate ◽

Mining Operations ◽

Overburden Pressure ◽

Filling Sequence ◽

Pore Water Pressures ◽

Backfilled Stopes ◽

Excess Pore

Underground backfilling offers significant economic and environmental advantages to mining operations. There is however a limited knowledge and understanding of how the backfill behaves within mine stopes, which creates some concern regarding the risk of accidents with potentially serious consequences. It is thus important to investigate further the response of backfill to ensure safe working conditions and optimize the filling sequence. This paper presents key results from a numerical study aimed at analyzing the hydrogeotechnical response of backfill in a narrow vertical stope. The simulations illustrate how stresses are influenced by stope geometry, water drainage, and filling rate. Three main cases are presented here to illustrate these effects; namely, (i) simulation of dry (or drained) backfill, (ii) a rapidly filled stope with progressive drainage and consolidation, and (iii) sequential backfill placement with different filling rates. The third case includes a simulation with evolving properties due to the binder added to the backfill. The results from the numerical analyses show that arching effects develop within narrow backfilled stopes because of the stiffness contrast between the rock and the fill material. This can produce a significant reduction of the stresses (horizontal and vertical) in comparison with the overburden pressure. The simulation results also show the development of excess pore-water pressures after the placement of the saturated backfill within the stope. Drainage tends to reduce these pressures and increase the frictional stresses along the rock walls. The sequentially filled stope simulations show that a rapid filling rate produces much higher total stresses and excess pore-water pressures, compared to slower rates. The simulation of the cemented backfill, with evolving properties, indicates that the progressive changes can have a significant effect on the total and effective stresses in the stope. A discussion follows on the implications of these results.

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Physical and numerical modelling of drainage and consolidation of tailings near a vertical waste rock inclusion

Canadian Geotechnical Journal ◽

10.1139/cgj-2020-0372 ◽

2020 ◽

Author(s):

Faustin Saleh-Mbemba ◽

Michel Aubertin

Keyword(s):

Pore Water ◽

Fine Particles ◽

Numerical Models ◽

Physical Modelling ◽

Waste Rock ◽

Coupled Processes ◽

Water Drainage ◽

Fine Grained ◽

Pore Water Pressures ◽

Tailings Impoundments

The use of waste rock inclusions in tailings impoundments is a recent technique that offers many advantages, but it also raises a few technical issues that must be addressed to optimize their design. A laboratory physical modelling study was conducted to assess the effect of waste rock inclusion on the behavior of initially saturated tailings in terms of drainage and consolidation. The evolution of pore water pressures and settlements after hydraulic deposition of the fine-grained tailings (slurry), with and without a drainage inclusion, has been monitored and analyzed. This investigation also focused on the evolution of the tailings void ratio and volumetric water content, the amount of water transferred to the waste rock, and the movement of fine particles at the interface between the two materials. The experimental results are used to demonstrate how such waste rock inclusion can affect tailings consolidation by reducing pore water pressures with accelerated water drainage, for various imposed conditions. The experimental data are also analysed with numerical models to better understand the coupled processes involved. A discussion follows on practical implications of the use of waste rock inclusions in tailings impoundments.

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Subglacial Hydrology for an Ice Sheet Resting on a Deformable Aquifer

Journal of Glaciology ◽

10.1017/s0022143000006833 ◽

1986 ◽

Vol 32 (110) ◽

pp. 20-30 ◽

Cited By ~ 80

Author(s):

E. M. Shoemaker

Keyword(s):

Pore Water ◽

Coulomb Friction ◽

Ice Sheet ◽

Friction Angle ◽

Water Channels ◽

Water Drainage ◽

Short Term ◽

Overburden Pressure ◽

Melt Water ◽

Pore Water Pressures

AbstractSubglacial hydrology is investigated for an ice sheet where the substrate consists of a deformable aquifer resting on an aquitard. If sliding velocities are low or absent, subglacial melt-water drainage is dominated by drainage through the aquifer to water channels. Drainage along the bed is negligible. Efficient melt-water drainage requires that a system of subglacial water channels exists; otherwise, pore-water pressures will exceed the overburden pressure. In general, aquifer deformation near (away from) the terminus is most likely to occur during the winter (summer). The effect of short-term high channel pressures is, in general, not critical to aquifer deformation because the pressure pulse does not propagate far into the aquifer. (For aquifers of high permeability, short periods of high channel pressures constitute the most critical condition.) Aquifer deformation at the terminus is very likely to occur if the terminus ice slope exceeds tanϕ, whereϕis the Coulomb friction angle of the aquifer material. Upwelling of basal melt water near the terminus will normally cause soil dilation if the aquifer has a low permeability (e.g. till). Maximal profiles are computed corresponding to various aquifer materials using channel spacings which provide efficient drainage. (A maximal profile is the highest ice profile which the aquifer can sustain without deformation.) In general, maximal profiles lie well above observed profiles (such ash(x) = 3x1/2(m)) except near the terminus. However, if channel spacings are sufficiently large, pore-water pressures are increased and maximal profiles can lie well belowh(x) = 3x1/2.

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