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<p>Structural collapse of loose granular materials has been documented as a primary trigger of catastrophic flow slides in tailings dams and hydraulic fills. While saturated soil collapse involves pore pressure generation, dry sand exhibits rapid volume contraction. Conventional triaxial systems cannot directly measure volume changes in dry specimens, limiting systematic comparison across saturation states. In this study, an inner-cell volume change measurement system was designed, calibrated, and integrated into an existing triaxial apparatus, providing high-precision volumetric measurements (± 0.4%) specifically designed for detecting collapse-related volume changes in dry sand. A comprehensive program of 32 monotonic triaxial tests was conducted on Firoozkooh sand, a clean quartz sand representative of hydraulically deposited materials, under undrained strain-controlled and drained q-constant loading paths with varying confining pressures and void ratios. Results demonstrate that collapse initiates when the stress path intersects the state boundary surface (SBS) in <i>e–p′–q</i> space. The collapse surface characteristics remained consistent between dry and saturated conditions, indicating that structural collapse is an intrinsic material response independent of drainage conditions. Moreover, mobilized friction angles at collapse were substantially lower than the critical state values, underscoring the potential for underestimating instability in conventional stability analyses of earthen structures.</p>

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Collapse Behavior of Loose Dry Sand Using a Modified Triaxial Apparatus with Inner Cell

  • 期刊论文

  • 发表日期：

    2025年11月22日

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  • Mahdi Talebi,
  • Manouchehr Latifi,
  • Abbas Ghalandarzadeh

摘要

Structural collapse of loose granular materials has been documented as a primary trigger of catastrophic flow slides in tailings dams and hydraulic fills. While saturated soil collapse involves pore pressure generation, dry sand exhibits rapid volume contraction. Conventional triaxial systems cannot directly measure volume changes in dry specimens, limiting systematic comparison across saturation states. In this study, an inner-cell volume change measurement system was designed, calibrated, and integrated into an existing triaxial apparatus, providing high-precision volumetric measurements (± 0.4%) specifically designed for detecting collapse-related volume changes in dry sand. A comprehensive program of 32 monotonic triaxial tests was conducted on Firoozkooh sand, a clean quartz sand representative of hydraulically deposited materials, under undrained strain-controlled and drained q-constant loading paths with varying confining pressures and void ratios. Results demonstrate that collapse initiates when the stress path intersects the state boundary surface (SBS) in e–p′–q space. The collapse surface characteristics remained consistent between dry and saturated conditions, indicating that structural collapse is an intrinsic material response independent of drainage conditions. Moreover, mobilized friction angles at collapse were substantially lower than the critical state values, underscoring the potential for underestimating instability in conventional stability analyses of earthen structures.