交通荷载作用下台阶式加筋土挡墙分级原理及计算理论研究

Multi-tiered geosynthetic-reinforced soil walls (MGRSW) have been applied widely in high embankment retaining soil structure recently. However, current design methodology in determining mode of tiered walls (e.g., numbers of tiered wall, height of walls and offset) is relative arbitrary and no rigorous theory is provided for practical engineering, especially the geosynthetic-reinforced soil walls subjected to long-term traffic loading will cause to potential engineering problem such as stability and extra deformation. Through stability analysis and model tests, this proposal will firstly investigate the intrinsic relationship between mode of tiered walls and interaction mechanism of retaining walls and failure modes under limit state, and then analyze the distributing pattern of stresses of retaining wall and reinforcement. Moreover, robust finite element methods for MGRSW will be put forward. Combing with some results from theoretical analysis, medium-scale and large-scale model tests and practical cases, study of effect of mode of tiered walls, properties of backfill and foundation soil and loads characteristics (e.g. magnitude and frequency) on the stress distribution and deformation of geosynthetics-reinforced soil retaining walls is conducted under the consideration of traffic loading, the pressure on foundation and parameters of reinforcement also will be optimized. At the same time, herein the item explores the changing trend of maximum horizontal deformation with coefficients of stability of MGRSW, and tentatively build the function reflecting the both relationships. Therefore, the stability evaluation method of MGRSW based on the horizontal deformation feature is obtained. Lastly, the proposal combines the results of stability with numerical analysis and puts forward the feasible theory of mode of tiered walls and calculating method for MGRSW. These will pave a good way for practical projects of MGRSW and guide actual projects design.

台阶式加筋土挡墙在高路堤支挡结构中得到了大量应用，但现有设计在确定分级模式(分级数、分级墙高和台阶宽度)时相对随意且缺乏理论依据，导致理论上难以有效地指导工程实践，而且路堤挡墙长期承受交通荷载作用会影响稳定与变形。项目拟通过稳定性分析和模型试验，重点研究极限状态下分级模式和各分级挡墙相互作用机理及破坏模式的内在联系，并以此为特征研究筋材拉力和挡墙应力的调配规律。进而构建高效的台阶式加筋土挡墙有限元数值方法，结合理论分析、中/大型模型试验和工程案例，深入研究交通荷载作用下分级模式、填土/地基土性质及荷载特征(大小和频率等)对台阶式加筋土挡墙受力与变形的影响，优化墙底地基土受力和筋材参数，并探寻挡墙面板最大水平位移与稳定系数之间的变化趋势或函数表达式，提出基于水平位移的台阶式加筋土挡墙稳定性判别方法。通过该项目的实施旨在提出台阶式加筋土挡墙的分级原理和计算理论，为其工程实践奠定良好的理论基础。

随着国内和“一带一路”沿线国家基础设施建设的发展，大量山区基础设施建设中高加筋土挡墙面临的筋材强度要求高和筋材用量激增的难题，分级台阶式加筋挡土墙作为一种有效的解决途径而被实践工程采用，但现有设计在挡墙分级模式方面相对随意且缺乏理论依据，导致理论上难以有效地指导工程实践，而且路堤挡墙长期承受交通荷载作用会影响稳定与变形。本项目针对这些关键科学问题，通过中型比尺模型试验、现场挡墙变形调查、数值计算和理论分析方法，首先系统地研究了分级模式、筋材性质、土体性质等对高加筋土挡墙受力与变形的影响，揭示了台阶式加筋土挡墙分级建造模式下加筋土挡墙应力调配规律，提出了地基土强度的适应性要求和加筋土挡墙分级基本原理。其次，综合考虑荷载等级和频率表征交通荷载，采用极限平衡方法分析挡墙稳定性，厘清了相邻分级加筋土挡墙的相互作用机理与分级模式、筋材参数和地基土性质的关系，揭示了分级台阶式加筋土挡墙相互作用机理及破坏模式。进而，系统研究了填土性质(内摩擦角和黏聚力)、地基土性质(弹性模量和抗剪强度指标)、筋材性质(刚度、长度和间距)，以及分级模式(墙高比、分级数和单级墙高)等因素对台阶式加筋土挡墙面板水平位移和稳定性的影响规律，构建了归一化的最大水平位移和加筋土挡墙稳定系数的量化关系，提出了基于水平位移的台阶式加筋土挡墙稳定性判别方法。最后，通过考虑筋材刚度随应变和时间的变化，提出了计算台阶式加筋土挡墙变形与力学性能的数值方法，模拟考虑施工过程、施工完成和后期运维阶段台阶式加筋土挡墙的变形和筋材受力，进而分析挡墙变形和筋材应力分布规律与荷载特征、分级模式和地基土性质等的相互关系，优化了加筋土挡墙的分级模式，提出交通荷载作用下台阶式加筋土挡墙分级原理及计算理论。本项目研究深化了高加筋土领域方面的加筋结构设计与理论知识，为台阶式加筋土挡墙设计和稳定性判别奠定了坚实基础。