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<p>The swelling properties of fully weathered expansive rock in the Taihang Tunnel of Shanxi, China, contribute to engineering hazards such as floor heaving, lining damage, and surrounding rock collapse. This study examines the swelling deformation behavior and mechanisms of remolded expansive rock from a tunnel in Shanxi. X-ray diffraction and scanning electron microscopy were employed to analyze the mineral composition and microstructural characteristics of the rock. Laboratory expansion tests were conducted to investigate the relationships between water content and expansion force, the no-load expansive rate, and the influence of varying water contents and overburden pressures on deformation behavior. For weakly expansive fully weathered rock, the interlayer content of illite-montmorillonite mixed layers constitutes 38%. The presence of significant intergranular fractures facilitates water infiltration into clay minerals, with swelling deformation primarily driven by interlayer expansion reactions and the diffusion of the electric double layer. Expansion force exhibits a negative linear relationship with water content, whereas the no-load expansive rate follows a negative hyperbolic trend. No-load expansion deformation progresses through three distinct stages: rapid, decelerated, and stable expansion. Approximately 80–90% of deformation occurs during the first two stages, with expansion ceasing at a water content of 20%. The saturated expansive rate decreases with increasing overburden pressure. At low pressures (<i>p</i> = 6.25&#xa0;kPa), the rate declines sharply with rising water content, reaching only 1.35% at 3% water content. Under higher pressures (<i>p</i> = 50&#xa0;kPa), the saturated expansive rate diminishes to 0.025% and becomes independent of water content. Loaded expansion tests and expansive force measurements confirm that the expansion force stabilizes near 50&#xa0;kPa. Based on these findings, this study elucidates the swelling mechanisms of expansive rock under both no-load and loaded conditions, along with their implications for tunnel stability and potential mitigation strategies.</p>

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Experimental Study of the Expansion of Fully Weathered Rock in Tunnels

  • 期刊论文

  • 发表日期：

    2025年7月6日

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  • Ming Zhang,
  • Junliang Liu,
  • Wei Wang

摘要

The swelling properties of fully weathered expansive rock in the Taihang Tunnel of Shanxi, China, contribute to engineering hazards such as floor heaving, lining damage, and surrounding rock collapse. This study examines the swelling deformation behavior and mechanisms of remolded expansive rock from a tunnel in Shanxi. X-ray diffraction and scanning electron microscopy were employed to analyze the mineral composition and microstructural characteristics of the rock. Laboratory expansion tests were conducted to investigate the relationships between water content and expansion force, the no-load expansive rate, and the influence of varying water contents and overburden pressures on deformation behavior. For weakly expansive fully weathered rock, the interlayer content of illite-montmorillonite mixed layers constitutes 38%. The presence of significant intergranular fractures facilitates water infiltration into clay minerals, with swelling deformation primarily driven by interlayer expansion reactions and the diffusion of the electric double layer. Expansion force exhibits a negative linear relationship with water content, whereas the no-load expansive rate follows a negative hyperbolic trend. No-load expansion deformation progresses through three distinct stages: rapid, decelerated, and stable expansion. Approximately 80–90% of deformation occurs during the first two stages, with expansion ceasing at a water content of 20%. The saturated expansive rate decreases with increasing overburden pressure. At low pressures (p = 6.25 kPa), the rate declines sharply with rising water content, reaching only 1.35% at 3% water content. Under higher pressures (p = 50 kPa), the saturated expansive rate diminishes to 0.025% and becomes independent of water content. Loaded expansion tests and expansive force measurements confirm that the expansion force stabilizes near 50 kPa. Based on these findings, this study elucidates the swelling mechanisms of expansive rock under both no-load and loaded conditions, along with their implications for tunnel stability and potential mitigation strategies.