高速铁路新型桩承式加筋低路堤荷载传递机理与动力稳定性研究

The novel geosynthetic-reinforced and pile-supported low embankment combining the advantages of traditional pile-supported embankment and new suspended net technology has good application prospect in the treatment of poor ground of high speed railway. The force and deformation behavior of the structure in which high strength geotechnical grille is fixed on the pile cap under dynamic load is complicated, and there is currently a lack of the systematic theoretical basis for design of this structure. Therefore, through the means of model test, numerical calculation and theoretical analysis, the microscopic motion law of filler particle when novel geosynthetic-reinforced and pile-supported low embankment with different pile spacing is filled is analysed. Then tensioned membrane of new double geosynthetic-reinforced cushion, soil arching effect in the embankment and interplay mechanism are studied to reveal the load transfer mechanism of the novel embankment structure. Considering the coupling effect of upper load and soil consolidation, the time variant characteristics of the force and deformation of the novel embankment structure are researched to demonstrate the evolution law of the tensioned membrane and soil arching effect of novel double geosynthetic-reinforced structure. Considering the dynamic fluid-solid coupling effect, the dynamic response index and variation law of macroscopic accumulated deformation of the novel embankment structure are researched, and analysis method of dynamic stability for the novel embankment is presented, so that to evaluate its dynamic stability. The research results can provide a theoretical basis for the design of the novel geosynthetic-reinforced and pile-supported low embankment.

高速铁路新型桩承式加筋低路堤结合了桩承式加筋低路堤传统技术和挂网技术的优点，在不良地基处理中具有广阔的应用前景，由于该结构将高强度格栅网固定于桩帽，加之受动力荷载作用，使其受力和变形行为较为复杂，目前设计仍缺乏系统的理论依据。为此，以高速铁路新型桩承式加筋低路堤为研究对象，通过模型试验、数值计算和理论分析等手段，分析不同桩间距的新型桩承式加筋低路堤在填筑过程中填料颗粒细观运动规律，研究垫层双层加筋网张拉膜效应和土拱效应及其相互影响机制，揭示新型桩承式加筋低路堤结构荷载传递机理；考虑上部荷载与地基土固结耦合效应，研究新型桩承式加筋低路堤受力与变形随时间的变化规律，揭示新型双层加筋网张拉膜效应和土拱效应时变规律；考虑动力流固耦合效应，研究新型桩承式加筋低路堤动态响应指标和累积变形的变化规律，提出其动力稳定性分析方法，评价其动力稳定性。该研究成果可为高速铁路新型桩承式加筋低路堤设计提供理论依据。

为了严格控制软土地区高速铁路桩承式加筋低路堤的沉降和不均匀沉降和提高其动力稳定性，结合公路领域的桩帽挂网技术，提出了一种垫层挂网+夹层网双层加筋模式的新型桩承式加筋低路堤型式，由于新型桩承式加筋低路堤桩帽挂网+垫层夹层网双层网的设计及其受到列车动力荷载的反复作用，致使其荷载传递机制和变形行为较为复杂。目前，新型桩承式加筋低路堤的垫层挂网+夹层网双层加筋技术在高速铁路低路堤路段地基处理中具有广阔的应用前景，然而其设计仍缺乏系统的理论依据。为此，本项目以新型桩承式加筋低路堤为研究对象，通过模型试验、数值计算和理论分析等开展了大量的研究工作，分析了新型桩承式加筋低路堤填料颗粒细观运动规律，研究了新型桩承式加筋低路堤受力与变形特征，揭示了新型桩承式加筋低路堤张拉膜效应和土拱效应的发展规律及其相互影响机制，掌握了其荷载传递规律，提出了不同低路堤高度对应的桩间距控制值，探明了新型桩承式加筋低路堤动力性能演化规律，建立了以新型桩承式加筋低路堤宏观累积沉降为主控指标的动力稳定性分析方法。本项目所取得的研究成果为新型桩承式加筋低路堤的设计提供理论支撑，对促进了新型桩承式加筋低路堤技术的推广应用具有重要实际意义。