膨胀土地基胀缩循环作用下高铁桩网结构路基土拱效应退化失效机理研究

桩网结构路基已被应用于膨胀土区高铁路基变形控制，虽然工程实践初步表明其适用性，但其荷载传递特性受地基胀缩变形的影响机制尚不明晰，理论滞后于工程应用。在长期、反复干湿循环条件下膨胀土桩网结构路基中，土拱效应退化是造成路基荷载传递特性动态演变的主控机制，而国内外相关研究鲜有报道。本项目拟通过干湿循环条件下膨胀土单元体试验和桩网结构路基平面应变模型可视化试验，揭示桩间土与格栅垫层相互作用机理；再结合桩网结构路基干湿循环三维模型试验研究，明确由地基反复胀缩变形引起的路基土拱形态演化规律，揭示路基土拱效应退化机理；进一步结合水力耦合数值仿真分析，揭示膨胀土胀缩变形对桩网结构路基荷载传递的影响机制，构建考虑膨胀土地基胀缩变形影响的桩网结构路基荷载传递模型，研究成果可为我国膨胀土区高铁桩网结构路基设计优化和长期变形控制提供理论支撑。

Geosynthetic-Reinforced Pile-Supported (GRPS) embankments have been widely used for deformation control in high-speed railway crossing expansive soil regions. Although the engineering practices proved its feasibility, but the changes in load transfer mechanism due to the swelling and shrinkage cycles of ground is still not well studied. Upon the long-term drying-wetting cycles of expansive soil ground, the degradation of soil arching within embankment is the key factor that governs the evolution of load transfer characteristics in GRPS embankments. However, very few studies have so far focused on this topic. In this project, drying-wetting cycles tests for expansive soil and visualized 2D plain strain GRPS embankment model tests will be carried out to study the interaction between soil and geosynthetic-reinforced cushion. Furthermore, 3D drying-wetting model tests will be performed to investigate the evolution of soil arch form in GRPS embankments when subjected to the swelling and shrinkage cycles of ground, aiming to reveal the degradation mechanism of soil arching. Finally, combined with results from hydro-mechanical coupled modelling of GRPS embankment, the evolution of load transfer mechanism due to the swelling and shrinkage of expansive soil will be studies, and an analytical model considering these effects will be developed. The outcome of this project will provide a theoretical basis for the optimal design and long-term deformation control of GRPS embankment for high-speed railways in expansive soil regions.