在役桩承式加筋路堤“土拱结构”劣化-重构力学行为长期演化规律研究

At present, the studies of geosynthetic reinforced and pile supported embankment (GRPS embankment) are concentrated in the static mechanical model under embankment load, and it has limitations. In reaction to the phenomenon,the concept of ‘soil arching structure’ is proposed by the applicant. In this study, the laboratory test, numerical analysis and theoretical analysis are employed to study the soil arching structure of GRPS embankment in service. The first, the dynamic critical height of existing soil arching under traffic loads is proposed and the mechanical model of soil arching is established in service embankment. Then this project aims at investigating the evolution law of soil arching structure through the creep behavior of geosynthetic or/and consolidation of subsoil, revealing the change law of load transfer mechanism of soil arching effect, tensioned membrane effect and support effect of subsoil during post-construction period. Finally, based on the research results mentioned above and previous research foundation, the simplified long-term mechanical model of GRPS embankment is established and the optimal design method is proposed. The research results in this project can perfect the design method of GRPS embankment and applied the construction of highway and railway, and they are significance in research and engineering practice.

针对目前桩承式加筋路堤研究主要集中于路堤荷载作用下静力学分析的局限性，申请人从细观角度提出了“土拱结构”概念，并从室内模型试验、离散元数值模拟及理论分析三个方面对在役桩承式加筋路堤土拱结构进行系统研究，提出交通荷载作用下既有土拱结构动力响应的临界高度Hc，并建立交通荷载作用下在役路堤土拱结构力学模型，揭示考虑筋材蠕变和（或）地基土固结的在役土拱结构劣化－重构长期演化规律，揭示路堤运营期间土拱效应-张拉膜效应-桩间土支撑作用荷载传递机理变化规律。最后，基于上述研究成果以及申请人前期研究基础，建立基于在役路堤长期力学行为的简化力学计算模型，提出考虑路堤长期性能的优化设计方法，研究成果可完善桩承式加筋路堤设计理论，指导其在工程中的应用与推广，具有重要的学术价值和工程意义。

针对目前桩承式加筋路堤研究主要集中于路堤荷载作用下静力学分析的局限性，项目以“在役桩承式加筋路堤”作为研究对象，基于室内模型试验，对“土拱结构”的形态特征及演化规律进行分析。试验通过摄影成像技术获取路堤填料位移场分布规律，研究“土拱结构”的形态特征，同时，结合桩土压力随桩土相对位移增大的变化规律，对“土拱结构”演化规律进行了初探；在此基础上，研究了路堤填筑高度及格栅加筋对“土拱结构”的影响。基于室内模型试验建立颗粒流数值分析模型，从宏细观角度对“土拱结构”的形成－演化机理进行综合分析，对相关宏观指标及细现指标的变化规律进行了系统分析。本文的研究成果对于深刻揭示桩承式加筋路堤的荷载传递机理具有重要的学术参考价值，对桩承式加筋路堤的工程实践也具有较重要的指导意义。