交通荷载下考虑路面-路基-地基相互作用的双向增强复合地基承载机理及变形特性研究

The composite foundation bidirectionally reinforced by geocell and stone columns is favored for civil engineers for its better service behavior. However, studies in this field primarily focus on statics, lacking in-depth research on bearing mechanism and deformation characteristic under traffic load. The interaction between rigid pavement, embankment and composite foundation is considered based on existing research. The dynamic constitutive model of soil is set up through cyclic triaxial tests. Several laboratory model tests are designed to deeply discuss the load transfer mechanism of pavement, embankment and composite foundation, the interaction between pile, soil and geocell, the evolution of soil arching. The bearing mechanism and deformation characteristic of bidirectional reinforced composite foundation under traffic load are analyzed with FEM and PFC numerical simulation technology. The settlement calculation mechanical model of composite foundation is established based on the theory of elastic foundation plate, when considering the dynamic load transfer mode and deformation compatibility of pavement, embankment and composite foundation. The energy-balance equation is presented based on the principle of minimum potential energy and solved by perturbation method with a proper displacement shape function introduced. A new settlement calculation method for bidirectional reinforced composite foundation is proposed considering the interaction between pavement，embankment and composite foundation finally.

土工格室+碎石桩双向增强复合地基因其良好的工作性能获得了工程界的青睐，但目前对该处治方法的研究多集中于静力学领域，对于交通荷载作用下该类复合地基的承载机理与变形特性尚缺乏系统深入的研究。本研究拟结合前人成果，考虑交通荷载下刚性路面、路基和复合地基相互作用，通过循环三轴试验，构建土体动力本构模型；设计多组室内模型试验，利用分布式光纤测量技术，深入探讨交通荷载下路面-路基-复合地基的荷载传递规律、桩-土-筋材相互作用机制、土拱效应演化规律等；在此基础上，基于有限元和颗粒流数值模拟技术，对交通荷载下双向增强复合地基的承载变形机理进行分析；最后，基于弹性地基板理论，考虑路面-路基-复合地基的动荷传递模式及变形协调，构建复合地基沉降计算力学模型，并基于最小势能原理，建立能量平衡方程，引入位移形函数，利用摄动法进行求解，从而提出一种交通荷载下虑路面-路基-地基相互作用的双向增强复合地基沉降计算方法。

土工格室+碎石桩双向增强复合地基因其良好的工作性能获得了工程界的青睐，但目前对该处治方法的研究多集中于静力学领域，对于交通荷载作用下该类复合地基的承载机理与变形特性尚缺乏系统深入的研究。项目开展了软土的循环动三轴试验，揭示循环动荷载下土体动应力应变特性，建立了典型湖区软土、路堤土及下卧层土体的动力本构模型。其次按照相似理论，设计并开展室内模型试验，研究不同幅值和频率的循环动荷载作用下，荷载沿刚性路面、路基向复合地基扩散传递的规律，得到了交通荷载下双向增强复合地基的承载及变形机理。在此基础上，基于有限元数值分析技术，构建了交通荷载下路面、路基、复合地基三维数值分析模型，深入分析交通荷载下路面、路基、复合地基体系的动荷载扩散、传递和衰减规律、桩土应力比及孔隙水压力分布规律等。.理论分析方面，综合考虑上部路面结构、路堤填土、土工格室加筋垫层相互作用，以及界面摩阻力和水平位移与垂直位移的耦合作用，将路堤上部的路面结构层，路堤填土层，土工格室或多层土工加筋垫层视作一个复合系统，土工格室或多层土工加筋垫层视作一个路堤填土层以下的梁高较浅的复合地基梁。考虑路面结构层的抗弯刚度，提出了一个扩展的双层Euler- Bernoulli梁模型在对称垂直荷载作用下的受力变形分析方法。此外，针对交通荷载的特点，基于双层Euler-Bernoulli梁模型，考虑加筋垫层的抗弯刚度以及路堤填土的重度，改进Euler-Bernoulli双层地基梁模型去预测交通荷载作用下的土工加筋路堤系统的性能。首先获得了路面结构层的弯曲刚度和土工合成材料加筋碎石垫层的修正的弯曲刚度，然后建立了移动荷载下土工加筋路堤的双层地基梁分析模型。与此同时，还考虑了上、下两层梁的耦合效应对上、下梁的动力响应的影响，并利用一阶摄动理论推导了双层梁系统的控制微分方程并获得了相应的解答，进而提出一种交通荷载下虑路面-路基-地基相互作用的双向增强复合地基沉降计算方法。