<p>This study examines the influence of compaction, initial degree of saturation, and suction on the deformation behavior of embankment soils under cyclic traffic loading. A series of undrained cyclic triaxial tests were conducted under constant mean principal stress conditions (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$p$</EquationSource> <EquationSource Format="MATHML"><math> <mi>p</mi> </math></EquationSource> </InlineEquation> constant) in both unsaturated (unsoaked) and soaked states. Soil specimens were initially prepared in unsaturated conditions at varying densities and saturation levels. For the soaked tests, specimens were subsequently saturated to simulate post-compaction wetting due to heavy rainfall. The initial suction immediately after compaction was recorded, and the accumulated axial strain (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\varepsilon_{a} )$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>ε</mi> <mi>a</mi> </msub> <mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> under cyclic loading was measured. In unsaturated tests, both pore water and air pressures were monitored to capture suction evolution during loading. The results revealed that <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\varepsilon_{a}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ε</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> generally decreased with decreasing saturation due to suction-induced stiffness. However, beyond a critical saturation threshold, <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\varepsilon_{a}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ε</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> began to increase despite higher suction values, indicating that high suction combined with unstable fabric conditions may compromise cyclic resistance and are prone to collapse. In all cases, soaked specimens exhibited greater <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\varepsilon_{a}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ε</mi> <mi>a</mi> </msub> </math></EquationSource> </InlineEquation> than their unsaturated counterparts, particularly when compacted at low initial saturation, highlighting the vulnerability of dry-compacted soils to post-wetting collapse. Notably, suction stress, defined as the product of initial suction and degree of saturation was found to effectively capture the interplay between hydraulic and mechanical factors influencing strain accumulation. Overall, the study highlights that the beneficial effects of suction on cyclic stability are strongly dependent on the underlying soil structure. The findings underscore the importance of optimizing initial compaction conditions and accounting for potential post-construction wetting to mitigate long-term deformation risks in embankment design.</p>

Cyclic Behavior of Unsaturated Sandy Soil: Effects of Compaction, Saturation, and Suction under Traffic-Like Loading

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发表日期：

2025年9月11日

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Bhargavi Chowdepalli,
Akshay Singh Rathore,
Kenji Watanabe

摘要

This study examines the influence of compaction, initial degree of saturation, and suction on the deformation behavior of embankment soils under cyclic traffic loading. A series of undrained cyclic triaxial tests were conducted under constant mean principal stress conditions ( $p$ $p$ constant) in both unsaturated (unsoaked) and soaked states. Soil specimens were initially prepared in unsaturated conditions at varying densities and saturation levels. For the soaked tests, specimens were subsequently saturated to simulate post-compaction wetting due to heavy rainfall. The initial suction immediately after compaction was recorded, and the accumulated axial strain ( $\varepsilon_{a} )$ $ε_{a})$ under cyclic loading was measured. In unsaturated tests, both pore water and air pressures were monitored to capture suction evolution during loading. The results revealed that $\varepsilon_{a}$ $ε_{a}$ generally decreased with decreasing saturation due to suction-induced stiffness. However, beyond a critical saturation threshold, $\varepsilon_{a}$ $ε_{a}$ began to increase despite higher suction values, indicating that high suction combined with unstable fabric conditions may compromise cyclic resistance and are prone to collapse. In all cases, soaked specimens exhibited greater $\varepsilon_{a}$ $ε_{a}$ than their unsaturated counterparts, particularly when compacted at low initial saturation, highlighting the vulnerability of dry-compacted soils to post-wetting collapse. Notably, suction stress, defined as the product of initial suction and degree of saturation was found to effectively capture the interplay between hydraulic and mechanical factors influencing strain accumulation. Overall, the study highlights that the beneficial effects of suction on cyclic stability are strongly dependent on the underlying soil structure. The findings underscore the importance of optimizing initial compaction conditions and accounting for potential post-construction wetting to mitigate long-term deformation risks in embankment design.