“…For any type of soil, the higher the confining pressure, the lower the k sat values, irrespective of the permeating liquid [ 23 ]. Increased confinement causes a reduction in pore spaces and increases the unit weight, thus reducing the hydraulic conductivity [ 30 ].…”
Section: Resultsmentioning
confidence: 99%
“…Therefore, to simulate the real field conditions, researchers proposed using FWP to evaluate k sat values. Experimental investigations on sand–Alqatif clay mixture revealed that k sat values reduced with an increase in confining pressure [ 23 ]. The generalized mechanism proposed for the reduction of k sat values using FWP is that an increase in confining pressure reduces the effective pore spaces, and an increase in unit weight leads to a reduction of effective flow paths.…”
The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic conductivity tests have been conducted on expansive clay using two different types of fibers (fiber cast (FC) and fiber mesh (FM)) exhibiting different surface morphological properties. The fiber parameters include their dosage (added at 0.2% to 0.6% by dry weight of soil) and length (6 and 12 mm). Commercially available lime is added to ensure proper bonding between clay particles and fiber materials, and its dosage was fixed at 6% (by dry weight of the soil). Saturated hydraulic conductivity tests were conducted relying on a flexible wall permeameter on lime-treated fiber-blended soil specimens cured for 7 and 28 days. The confining pressures were varied from 50 to 400 kPa, and the saturated hydraulic conductivity values (ksat) were determined. For FC fibers, an increase in fiber dosage caused ksat values to increase by 9.5% and 94.3% for the 6 and 12 mm lengths, respectively, at all confining pressures and curing periods. For FM fibers, ksat values for samples mixed with 6 mm fiber increased by 12 and 99.2% for 6 and 12 mm lengths, respectively for all confining pressures at the end of the 28-day curing period. The results obtained from a flexible wall permeameter (FWP) were compared with those of a rigid wall permeameter (RWP) available in the literature, and the fundamental mechanism responsible for such variations is explained.
“…For any type of soil, the higher the confining pressure, the lower the k sat values, irrespective of the permeating liquid [ 23 ]. Increased confinement causes a reduction in pore spaces and increases the unit weight, thus reducing the hydraulic conductivity [ 30 ].…”
Section: Resultsmentioning
confidence: 99%
“…Therefore, to simulate the real field conditions, researchers proposed using FWP to evaluate k sat values. Experimental investigations on sand–Alqatif clay mixture revealed that k sat values reduced with an increase in confining pressure [ 23 ]. The generalized mechanism proposed for the reduction of k sat values using FWP is that an increase in confining pressure reduces the effective pore spaces, and an increase in unit weight leads to a reduction of effective flow paths.…”
The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic conductivity tests have been conducted on expansive clay using two different types of fibers (fiber cast (FC) and fiber mesh (FM)) exhibiting different surface morphological properties. The fiber parameters include their dosage (added at 0.2% to 0.6% by dry weight of soil) and length (6 and 12 mm). Commercially available lime is added to ensure proper bonding between clay particles and fiber materials, and its dosage was fixed at 6% (by dry weight of the soil). Saturated hydraulic conductivity tests were conducted relying on a flexible wall permeameter on lime-treated fiber-blended soil specimens cured for 7 and 28 days. The confining pressures were varied from 50 to 400 kPa, and the saturated hydraulic conductivity values (ksat) were determined. For FC fibers, an increase in fiber dosage caused ksat values to increase by 9.5% and 94.3% for the 6 and 12 mm lengths, respectively, at all confining pressures and curing periods. For FM fibers, ksat values for samples mixed with 6 mm fiber increased by 12 and 99.2% for 6 and 12 mm lengths, respectively for all confining pressures at the end of the 28-day curing period. The results obtained from a flexible wall permeameter (FWP) were compared with those of a rigid wall permeameter (RWP) available in the literature, and the fundamental mechanism responsible for such variations is explained.
“…The clayey matrix occupied the sand voids and contacts between the sand grains as the clay content increased, thereby increasing the compressibility of sample c and reducing the tendency to dilate. The compressibility is closely related to the hydraulic conductivity of the sand–clay mixtures 24 . Figure 5 Effect of the clay content and the confining pressure on the normalized pore water pressure versus the axial strain response curves: ( a ) clean sand and ( b ) 30% clay content.…”
This study investigated shear strength behaviour of compacted sand–clay mixtures used as liners, with 10%, 20%, and 30% clay contents. A natural high-plasticity and highly expansive clay found in the eastern province of Saudi Arabia was used. A series of consolidated undrained triaxial tests and pore water pressure measurements of saturated samples with various clay contents and confining pressures was conducted using a computer-controlled Bishop and Wesley triaxial cell. The unit was equipped with pressure volume controllers and a pressure transducer for measuring sample volume changes and excess pore water pressure. The experimental test results indicate that clay content and confining pressure significantly affect stress strain response curves, pore water pressure generation curves, and steady-state shear strength. Sand–clay mixtures with clay content less than 10% showed a tendency toward contractive behaviour. The failure line slope increased in accordance with clay content increase. The deviator stress versus axial strain of saturated sand–clay mixtures indicated a hyperbolic trend. The stress ratio versus axial strain representation was more informative for the shear strength behaviour assessment. Clay content did not significantly affect critical-state friction angle. Scanning electron microscope images of the sand-clay mixtures with different clay contents are presented.
“…Tavenas et al (1983) suggested that indirect assessments are unreliable because of the assumptions made in the analysis. Chapuis (2012) and Dafalla et al (2015) suggested that Equ (3) under predicts the hydraulic conductivity by two to three orders of magnitude.…”
Many natural soils and artificial soils are composite soils formed of a range of particle sizes and types. These soils are often difficult to sample and test when following standard site investigation practice thus it is necessary to resort to empirical correlations, most of which were developed for either coarse-grained (e.g. clean sands) or fine-grained (e.g. pure clays) soils. The hydraulic conductivity of clean sands is a function of the void ratio and particle size distribution, and for clays, the clay type and void ratio. This suggests that the hydraulic conductivity of composite soils will be a function of these properties and the clay content. Composite soils formed of four clay minerals and two sands were consolidated from slurry to determine the variation of hydraulic conductivity with clay content, clay type and void ratio. With matrix dominated soils, soils that contain with more than 35% fines content, the flow is a function of the matrix void ratio and clay type; and, for clast dominated soils, soils that contain less than 20% fines content, the intergranular void ratio and particle size distribution. The behaviour of soils with a fines content between 20% and 35% depends on the confining pressure and density.
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