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<p>Excavation unloading during engineering construction and water absorption-induced swelling of mudstone are two core causes of time-dependent arching deformation in mudstone subgrades. To elucidate the wet-swelling deformation mechanism of mudstone subgrades and quantify the influence of unloading, two mudstone subgrade models were constructed based on similarity principles—one without unloading (Model I) and the other simulating deep cutting excavation unloading (Model II)—and model tests were conducted by simulating rainfall infiltration and groundwater rise, coupled with synchronous monitoring of stress, humidity, and deformation. The results show that water in both models undergoes a dynamic “unsaturated-saturated” seepage process with water content gradually increasing to a stable state, and wet-swelling deformation aligns with humidity variations, exhibiting three stages of rapid deformation, followed by slow deformation, and finally deformation stabilization; unloading drives the internal stress of Model II to evolve through three stages of rapid attenuation, decelerated attenuation, and stress stabilization, where the closer to the model surface, the greater the stress reduction, initial stress change rate, and time required for unloading-induced stabilization, and the influence of unloading becomes negligible at depths below 58&#xa0;cm, while the damage variable <i>D</i> decreases exponentially with increasing unloading depth, indicating significantly more severe damage in shallow regions than in deep ones. Additionally, unloading does not alter the fundamental “humidity-driven deformation” behavior of mudstone but markedly enhances the water content, initial permeability coefficient, and wet-swelling deformation of Model II, with the increase rate of water content decreasing exponentially with depth, and the maximum wet-swelling deformation and rapid deformation rate of Model II being 2.44 times and 5.25 times those of Model I, respectively. A calculation model for the wet-swelling strain of unloading-damaged mudstone was further established and validated using experimental data, providing valuable insights for the deformation control of mudstone subgrades subjected to both unloading and hydrological effects.</p>

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Model test study on the influence of unloading-water interaction on wet-swelling deformation of high-speed railway mudstone subgrade

  • 期刊论文

  • 发表日期：

    2025年10月24日

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  • Li Pei,
  • Huafeng Deng,
  • Tingfeng Zhang,
  • Yitian Zhang,
  • Xiaoliang Xu,
  • Jianlin Li

摘要

Excavation unloading during engineering construction and water absorption-induced swelling of mudstone are two core causes of time-dependent arching deformation in mudstone subgrades. To elucidate the wet-swelling deformation mechanism of mudstone subgrades and quantify the influence of unloading, two mudstone subgrade models were constructed based on similarity principles—one without unloading (Model I) and the other simulating deep cutting excavation unloading (Model II)—and model tests were conducted by simulating rainfall infiltration and groundwater rise, coupled with synchronous monitoring of stress, humidity, and deformation. The results show that water in both models undergoes a dynamic “unsaturated-saturated” seepage process with water content gradually increasing to a stable state, and wet-swelling deformation aligns with humidity variations, exhibiting three stages of rapid deformation, followed by slow deformation, and finally deformation stabilization; unloading drives the internal stress of Model II to evolve through three stages of rapid attenuation, decelerated attenuation, and stress stabilization, where the closer to the model surface, the greater the stress reduction, initial stress change rate, and time required for unloading-induced stabilization, and the influence of unloading becomes negligible at depths below 58 cm, while the damage variable D decreases exponentially with increasing unloading depth, indicating significantly more severe damage in shallow regions than in deep ones. Additionally, unloading does not alter the fundamental “humidity-driven deformation” behavior of mudstone but markedly enhances the water content, initial permeability coefficient, and wet-swelling deformation of Model II, with the increase rate of water content decreasing exponentially with depth, and the maximum wet-swelling deformation and rapid deformation rate of Model II being 2.44 times and 5.25 times those of Model I, respectively. A calculation model for the wet-swelling strain of unloading-damaged mudstone was further established and validated using experimental data, providing valuable insights for the deformation control of mudstone subgrades subjected to both unloading and hydrological effects.