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Coupled groundwater fluctuation and wetting–drying effects on fissured expansive soil canal slopes: hydro-mechanical evolution from physical model testing
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DOI：10.1007/s11440-026-03201-4.png)
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Abstract
En 中文
Deep excavated expansive soil canal slopes often exhibit progressive deformation under coupled groundwater level fluctuation, wetting–drying cycles, and inherent fissures, yet the mechanisms linking preferential water migration to long-term hydro-mechanical degradation remain insufficiently constrained. Here, a 10:1 large-scale physical model was constructed with a symmetric comparative design (fissured versus intact) to investigate moisture redistribution, matric suction attenuation, pore pressure evolution, and internal deformation under four wetting–drying cycles followed by a prolonged rainfall stage, while groundwater level was actively regulated between 30 and 100 cm. Results show that inherent fissures reorganize seepage into a dual-structure comprising preferential flow along fissures and delayed redistribution within the soil matrix, producing persistent hydraulic heterogeneity and dynamically migrating seepage outlets. In the deeper zone, pore water pressure is primarily governed by groundwater fluctuation; however, the fissured slope exhibits consistently higher toe pressures and an earlier transition from localized retention to efficient drainage as fissure connectivity increases. Repeated cyclic loading induces irreversible attenuation of matric suction, particularly in the fissured deep zone where suction recovery becomes negligible after the early cycles, accompanied by accelerated downslope and vertical displacements with a distinct lag behind suction loss, indicating cumulative plastic deformation. The coupled action of groundwater fluctuation and fissure-network evolution drives a regime transition from matrix-controlled seepage to preferential flow dominance, ultimately facilitating toe heave, rill erosion, and shallow sliding. These findings provide experimental evidence and a conceptual framework for degradation-driven progressive instability in deep fissured expansive soil canal slopes, informing long-term risk assessment and stability management in similar engineering settings.
Keywords:
Expansive soil slope
Groundwater fluctuation
Hydro-mechanical evolution
Inherent fissures
Matric suction
Preferential flow
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