Pore structure effects on the water retention behaviour of a compacted silty sand soil subjected to drying-wetting cycles

Ng, Charles Wang Wai; Peprah-Manu, Daniel

doi:10.1016/j.enggeo.2022.106963

Cited by 33 publications

(7 citation statements)

References 59 publications

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“…However, the mechanism of the capillary barrier is based on the k usat of different materials, which is controlled by the water retention behavior and k sat . According to previous studies [43][44][45], the water retention behaviors of soils (e.g., sand, silt and clay) are significantly changed by freeze-thaw cycles and wetting-drying cycles. Mu et al (2020) [43] reported that both the air-entry value and degree of hysteresis of loess decreased with the increase in wetting-drying cycles.…”

Section: Future Outlookmentioning

confidence: 94%

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

Meng,

Xia,

Xia

et al. 2024

Geosciences

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Mine tailings have shown viability as the fine–grained layer in a capillary barrier structure for controlling acid mine drainage in a circular economy. Their saturated hydraulic conductivities (ksat) under wetting–drying cycles and freeze–thaw cycles remain unexplored. In this study, modified tailings with a weight ratio of 95:5 (tailings/hydrodesulfurization (HDS) clay from waste–water treatment) and an initial water content of 12% were used. The ksat of specimens was measured after up to 15 wetting–drying cycles, each lasting 24 h, with a drying temperature of 105 °C. The ksat for wetting–drying cycles decreased from 3.9 × 10−6 m/s to 9.5 × 10−7 m/s in the first three cycles and then stabilized in the subsequent wetting–drying cycles (i.e., 5.7 × 10−7 m/s–6.3 × 10−7 m/s). Increased fine particles due to particle breakage are the primary mechanism for the ksat trend. In addition, the migration of fines and their preferential deposition near the pore throat area may also promote this decreasing trend through the shrinking and potentially clogging–up of pore throats. This could be explained by the movement of the meniscus, increased salinity, and, subsequently, the shrinkage of the electrical diffuse layer during the drying cycle. Similar specimens were tested to measure ksat under up to 15 freeze–thaw cycles with temperatures circling between −20 °C and 20 °C at 12 h intervals. Compared to the untreated specimen (i.e., 3.8 × 10−6 m/s), the ksat after three freeze–thaw cycles decreased by 77.6% (i.e., 8.5 × 10−7 m/s) and then remained almost unchanged (i.e., 5.6 × 10−7 m/s–8.9 × 10−7 m/s) in subsequent freeze–thaw cycles. The increased fine grain content (i.e., 3.1%) can be used to explain the decreased ksat trend. Moreover, the migration of fines toward the pore throat area, driven by the advancing and receding of ice lens fronts and subsequent deposition at the pore throat, may also contribute to this trend.

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Section: Future Outlookmentioning

confidence: 94%

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

Meng,

Xia,

Xia

et al. 2024

Geosciences

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“…Its lateral boundary is assumed to be fully constrained. After the test, a gap between the sample and ring needs to be checked to verify that there is no shrinkable lateral deformation [13]. The changes in void ratio and degree of saturation were calculated by recording data of vertical displacement and inflowing or outflowing of pore water.…”

Section: Test Apparatusmentioning

confidence: 99%

“…The one-dimensional consolidation test was then conducted with the vertical net stress from 1 kPa to 1600 kPa stepwise. During the test, the equilibration state was judged by the criteria that the water flow rate was <8×10 -13 m 3 /s, and vertical displacement was less than 0.002 mm/day [13]. The water pressure was kept at a constant value of 20 kPa.…”

Section: Test Procedures 231 Sample Preparationmentioning

confidence: 99%

Experimental study on compression behaviours of compacted sandy loam using a Modified State Surface Approach

Li,

Cui,

Geng

2024

IOP Conf. Ser.: Earth Environ. Sci.

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It is essential to study the deformation of unsaturated soil to predict the settlement of constructed embankments and foundations under precipitation and external loadings. This study conducted suction-controlled and stress-controlled oedometer tests on compacted sandy loam. The void ratio and degree of saturation were measured to study the deformation behaviours of unsaturated soil. The acquired data were analyzed using a modified state surface approach (MSSA). It was found that for the samples with an identical initial state, a unique state surface can be employed to describe the change of void ratio in an e-σ v’-s space, which consists of an elastic session and a plastic collapsible session. After yielding, the LC yield curve expands along the plastic collapsible surface with increasing loading or decreased suction, accompanied by irrecoverable plastic deformation. Along the hydraulic wetting paths (suction decreasing), the soil exhibits expansive deformation in the elastic surface but collapses into plastic collapsible after yielding. Differing from deformation behaviours, this study also demonstrated that the degree of saturation (S r) cannot be plotted in a unique surface in S r-σ v’-s space regarding hydraulic wetting and mechanical compression. This can be interpreted by different mechanisms of increasing S r by adsorbing water and mechanical compression.

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“…The SWRC is an essential component of unsaturated soil used to analyze the hydromechanical properties of unsaturated soils [22]. It frequently appears as an association between the vacuum logarithm and the Sr, w, or Θw [23]. As a consequence of day-to-day and seasonal weather fluctuations, unsaturated soils experience desorption and adsorption cycles.…”

Section: Hysteresis In Swrc and Swccmentioning

confidence: 99%

Hysteresis in Soil, Its Causes and Influences

Nasr,

Ati

2023

IOP Conf. Ser.: Earth Environ. Sci.

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Soil hysteresis is a natural phenomenon that occurs in soil water retention curve (SWRC) and soil water characteristic curve (SWCC), the mismatch of the drying (drainage or desorption) and wetting (sorption or adsorption) curves in each curve is called hysteresis in soil, i.e., At any potential (Ψ), there is a discrepancy between the soil water content (Θ or ű) in the curve of desorption and adsorption, this indicates that the amounts of water collected during the desorption cycle are not the same as the amount of water for adsorption the soil at the same applied pressure (suction Ψ). So, this relationship between soil water content (Θ or ű) versus soil water potential (Ψ) is non-unique. The difference is caused by a number of mechanisms, including: Contact Angle (θ), Adsorption, Bubble-form, Matric potential, Ink-Bottle Effect, Entrapped Air, Wetting and Drying History and Pore Size... etc. The explanations concern both (water and soil). Soil hysteresis has a degree, that varies depending on the type of clay minerals and pore size... etc. In this review paper, what are the causes of soil hysteresis, the hysteresis degree, and what does it influence? will be discussed.

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Pore structure effects on the water retention behaviour of a compacted silty sand soil subjected to drying-wetting cycles

Cited by 33 publications

References 59 publications

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

Effect of Freeze–Thaw and Wetting–Drying Cycles on the Hydraulic Conductivity of Modified Tailings

Experimental study on compression behaviours of compacted sandy loam using a Modified State Surface Approach

Hysteresis in Soil, Its Causes and Influences

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