Hydraulic behaviour of dune sand-bentonite mixtures under confining stress

Abstract

Compacted layers of sand-bentonite mixtures have been proposed and used in a variety of geotechnical projects as engineered barriers for the enhancement of impervious landfill liners, cores of zoned earth dams and radioactive waste repository systems. In the practice we try to get an economical mixture that satisfies the hydraulic and mechanical properties specified by regulation rules. The effect of the bentonite additions on the mixture is reflected by its capability of clogging the matrix pores upon swelling. In order to get an adequate dune sand-bentonite mixture, an investigation on hydraulic and mechanical behaviours is carried out in this study for different mixtures. Using oedometer test, the adequate bentonite addition to the mixture, which satisfies the conditions on permeability, is found to be around 12% to 15 %. These results are also confirmed by direct measurement using triaxial cell.

Predicting Hydraulic Conductivity for Flexible Wall Conditions Using Rigid Wall Permeameter

“…Very high confining stresses of more than 200 kPa occur at a rather deep level if we consider only the weight of saturated soil as an overburden pressure. These observations are in agreement with those reported by [23,24,26,28].…”

“…The parent material from which the clay particles were formed is of significant influence and normally varies from one area to another area [33]. Gueddouda et al [24] carried out extensive research on the impact of ion concentration in water, cation exchange capacity and the double-layer theory on the hydraulic and mechanical properties of expansive soils.…”

“…Tavenas et al and Dafalla et al [22,23] used the consolidation tests as an indirect approach to measure the hydraulic conductivity of sand-clay mixtures. Flexible sidewall permeability testing became popular during the last two decades and is used by many investigators [13,[23][24][25][26][27][28][29] as it allows simulating the actual field condition with regard to the control of the lateral earth pressure and the hydraulic gradient. The ASTM D5084 standard method uses flexible sidewall parameters and is mostly recommended for projects sensitive to hydraulic conductivity such as compacted clay liners (CCL).…”

Modeling added spatial variability due to soil improvement: Coupling FEM with binary random fields for seismic risk analysis

“…The initial mixture, shown in purple, presents the highest reduction of about 40%. The first case corresponds to a 5% Bentonite permeation on sand, shown in orange, which as measured by Gueddouda et al [53] produces a decrease in κ of one order of magnitude (i.e. for this case, = − κ 10 m/s 5…”

Valorisation of dune sand-tuff for Saharan pavement design

“…A specific amount of mixture was weighed, added to the mould and then compacted to a single layer of 100 mm in height and density of the MPO condition [2,57]. This method leads to a homogeneous distribution of the compaction stress [57,58] and also avoids trim of the specimen to preserve the initial structure. These statically compacted specimens were divided into two groups.…”