考虑各向异性的粒料基层沥青道面安定行为与变形控制

Asphalt pavement with granular base has obvious advantages including smooth, good skid resistance, shock absorption, crack prevention and easy maintenance. However, it is easy to produce rutting distress. Due to the characters of complex landing gears and high-speed multi-attitude motion of the new generation large aircrafts, the aircraft loads significantly enhance the stress superposition effect, and then induce the large horizontal force and principal stress rotation. This effect would also change the deformation characteristics of anisotropic materials and intensify the generation of rutting. The traditional design method is based on the assumption of isotropy and static aircraft loads, which is inappropriate to meet the requirements of pavement deformation control under complex loads. In this project, the real stress level and stress path of anisotropic structure under aircraft dynamic behavior will be investigated by three-dimensional finite element simulation and influence surfaces method. The hollow cylinder torsional shear tests and true triaxial tests will be used to reveal the plastic cumulative strain laws of soil and granular material under principal stress rotation and triaxial stress state. The cumulative strain model of soil and granular materials will be selected to investigate the shakedown behavior of anisotropic structures under real stress. Based on optimized iterative search algorithms, a critical shakedown limit calculation model of layered structures considering anisotropic property will be constructed, and a deformation control method based on shakedown theory will be proposed. Precise simulation, accurate expression and reasonable control of shakedown deformation behavior of asphalt pavement with granular base course will be realized in this project, which is able to provide technical reserve of application of shakedown theory in airport asphalt pavement design.

粒料基层沥青道面具有平整抗滑、减震防裂、易维修的显著优势，但易产生轮辙病害。新一代大型飞机的复杂起落架构型和多姿态高速运动特征，将显著增强应力叠加效应，诱发大水平力和主应力轴旋转现象，改变各向异性材料变形特征，加剧轮辙的产生。以静态荷载和各向同性为假设的传统设计方法，将难以适应复杂荷载下道面变形控制要求。项目运用三维有限元精细模型和影响面法，研究飞机复杂地面动力行为下各向异性结构真实应力水平和应力路径；利用空心圆柱扭剪和真三轴试验，揭示主应力轴旋转和三向应力状态下道基土和粒料累积应变规律；甄选合适的累积应变模型，研究真实应力作用下的各向异性结构累积变形规律和安定行为；基于优化迭代搜索算法，构建考虑各向异性的层状体系结构临界安定极限计算模型，提出基于安定理论的变形控制方法。最终实现粒料基层沥青道面安定变形行为的精细模拟、准确表达和合理控制，为安定理论在机场沥青道面设计中的应用提供技术储备。

粒料基层沥青道面具有平整抗滑、减震防裂、易维修的显著优势，但易产生轮辙病害。新一代大型飞机的复杂起落架构型和多姿态高速运动特征，将显著增强应力叠加效应，诱发大水平力和主应力轴旋转现象，改变各向异性材料变形特征，加剧轮辙的产生。以静态荷载和各向同性为假设的传统设计方法，将难以适应复杂荷载下道面变形控制要求。本项目围绕机场重载粒料基层沥青道面轮辙变形控制问题，构建了复杂飞机荷载下各向异性粒料基层沥青道面三维有限元模型，研究粒料本构模型和各向异性系数、不同飞机荷载形式、层间系数、结构组合等因素对各向异性结构真实力学响应的影响，为粒料的数值试验荷载水平、粒料基层的变形特征分析提供了依据；构建了复杂真实形态的粒料颗粒，基于自主开发的离散元三轴应力伺服控制程序，精细控制粒料材料三轴加载应力，最终建立了基于离散元的粒料颗粒流动真三轴仿真模型。以力学响应分析得到的真实应力状态为输入条件，研究分析三向应力状态对各向异性粒料累积应变的影响，采用安定理论揭示了不同应力水平下的粒料变形行为。解析了粒料的安定临界区间，以主应力比n为自变量，最大轴压为因变量，计算了塑性安定临界区间与塑性蠕变临界区间上下界，并拟合得到临界区间方程。对152种工况进行拟合分析，甄选合适的塑性累积应变预估模型后，提出了适应安定变形三阶段的粒料累积应变预估模型，并提出了以0.03作为粒料基层临界应变值；采用应变、应变变化率双重控制，计算粒料基层的塑性安定临界应力与最大荷载作用次数，采用基层的层顶竖向应力与设计荷载作用次数作为设计指标，提出了沥青道面粒料基层永久变形控制方法。研究成果将实现粒料基层沥青道面结构安定变形行为的精细模拟、精确表达和合理控制，为机场沥青道面的设计理论和方法提供参考。