Physicochemical analysis of permeability changes in the presence of zinc

Water retention characteristics of swelling clays in different compaction states

“…6). Table 2 presents the percentage inter-aggregate and intraaggregate pores and the dominant pore diameter (Souli et al, 2008) for intact and compacted specimens, obtained by employing the modified van Genuchten bimodal equation, refer Eqn. 3 (Dieudonne et al, 2014;Lopes et al, 2014).…”

Fluid flow and effective conductivity calculations on numerical images of bentonite microstructure

“…Depending on the initial fabric of the bentonite, connected flow paths of inter-aggregate pores may not exist (Bouchelaghem and Jozja, 2009b;Souli et al, 2008). In that case, according to the local description given in Sections 2.4 and 2.5, fluid flow in the clay aggregates is described by Darcy's law Eq.…”

Analytical Determination of Flow Patterns in a Double Porosity Medium Containing Ellipsoidal Occluded Macro-Voids

“…Therefore, if we look at pure clay at the mesoscopic scale after pollutant permeation, in the absence of quartz grains or other impurities (or if their proportion is negligible), clay aggregates and inter-aggregate voids co-exist. This arrangement creates a porous medium with two distinct length scales in it, while under the effect of inter-aggregate void development, the overall permeability measured on a macroscopic sample using Darcy's law is shown to increase notably (Jozja 2003;Jozja et al 2003;Souli et al 2008).…”

“…Owing to the high level of compaction pressures employed, the inter-particle pore space is of the same order of magnitude as the inter-layer spacing, and inter-aggregate voids are not present within the initial microstructure, prior to pollutant permeation. In contrast, after permeation of lead nitrate and zinc solutions under mechanical compaction, Scanning Electron Microscopy, using the technique of cryo-fracturing, has displayed the formation of inter-aggregate pores (of diameter > 1.5 μm), which may be connected or not depending on the initial degree of organization within the clay material considered (Jozja 2003;Jozja et al 2003;Souli et al 2008). Therefore, if we look at pure clay at the mesoscopic scale after pollutant permeation, in the absence of quartz grains or other impurities (or if their proportion is negligible), clay aggregates and inter-aggregate voids co-exist.…”

“…In the case of non-connected macro-voids, the situation is completely different, as fluid flow within occluded macro-voids is a consequence of the flow occurring within the surrounding clay matrix. The determination of pore fluid velocity and excess pore fluid pressure in the latter case, which has not been investigated as thoroughly as the connected voids case, would then allow to model permeability evolution in well-ordered clays such as Wyoming bentonite (Jozja 2003) or other montmorillonites (Souli et al 2008) under pollutant permeation, as well as to gain insight into the transition regime, during micro-aggregate breaking and before flow paths get connected. At this point, it is important to stress that among factors causing an increase in hydraulic conductivity in clays during infiltration of polluting species, structural modifications induced at the intermediate scale of clay aggregates are rarely dealt with (Jozja et al 2003).…”