基于主曲线的沥青混合料多子午线破坏准则及黏弹性影响研究

The rutting damage of asphalt pavement is a viscoelastic plastic cumulative deformation process under constantly changing of temperature, load frequency and pressure-tension-shear stress state. It is difficult to simulate the change of the rotation of the stress axis under the actual traffic load by the conventional research method. And the effect on the viscoelasticity failure is also rarely considered. Based on the theory of torsional shear tri-axial test and specimens of hollow cylinder asphalt mixture，the project considers temperature, loading rate / frequency, and the graded confining pressures. 1) By applying four static loading methods with axial compression, axial tension, pure torsion and compression-torsion in coordination which could realize the principal stress axis orientation deflection, the failure load and deformation on the meridian lines of compression, stretching, pure shear and compression-shear are obtained. Based on the research of the principal curves of the failure principal stress, the failure principal strain, and the stiffness modulus, the multi-meridian failure criterion model combined with meridian lines of compression, extension, and shear are investigated. 2) The constant amplitude oscillation failure test and repeated creep recovery failure test under pure torsion and compression-torsion are carried out respectively. The complex stiffness modulus and creep compliance in the 2 meridian planes of pure shear and compression shear, and the parameters of the viscoelastic eigenvalue under steady and critical failure, are obtained. Then the principal curves are also set up. Through the analysis of the function correlation of the principal curve such as the stiffness modulus of the static load, the effect of the viscoelasticity on the failure process is acquired. The expected results will provide guidance for the theoretical and experimental research on the strength simulation and non-isotropy of the asphalt mixture in the complex stress state.

沥青路面车辙损坏是在温度、荷载频率及压-拉-剪应力状态不断变化下的黏弹塑性累积变形过程，常规研究难以模拟实际交通荷载作用下应力主轴旋转变化的特点，亦较少考虑黏弹性破坏的影响。项目基于扭剪三轴原理及中空圆柱沥青混合料试件，考虑温度、加载速率/频率，在分级围压下：1)采用轴压、轴拉、纯扭及压扭比例协同加载4项静载破坏试验，实现应力主轴定向偏转，获得压缩、拉伸、纯剪、压剪子午线的破坏荷载及变形，在建立破坏主应力、主应变、劲度模量等主曲线的基础上，研究压-拉-剪多子午线破坏准则模型；2)分别进行纯扭、压扭下的等幅振荡、重复蠕变回复4项黏弹性破坏试验，获得纯剪、压剪子午面内的复数劲度模量、蠕变柔量及其稳态、临界破坏下的特征值参数，并建立主曲线，通过与静载劲度模量等主曲线的函数相关性分析，获得黏弹性对破坏过程的影响。预期成果将为沥青混合料在复杂应力状态下的强度模拟、非各向同性的理论与试验研究提供指导。

本项目旨在通过三轴扭剪试验方法达到真实模拟交通荷载作用下沥青路面结构中的应力主轴旋转变化并建立拉-压-纯-压扭多子午线强度模型的目的。. 首先解决了3个主要问题:1)自主设计加工、组装调试研制3套扭剪试验设备，适于不同温度、不同加载速率及量程的三轴扭剪破坏强度试验和动态黏弹性及重复蠕变回复试验；2)比较研究方形截面棱柱体、实心圆柱体和空心圆柱体3种沥青混合料试件的成型方法、质量及试验效果，重点针对传统静压成型法进行改进，采用双面静压、专用内外模具及成型参数检验等；3)基于沥青混合料细观结构的有限元、离散元和界面单元3种数值模拟计算方法，分析试件扭剪三轴力学性能及实际加载装置对试件端部约束/放松效果的影响。. 在此基础上，进行了破坏强度、动态黏弹性及重复蠕变回复试验研究，主要结果包括:1)获得不同温度及加载速率下的压缩、拉伸、纯剪、压剪子午线破坏强度、模量及变形等参数，采用线性模型及西格摩德(Sigmoidal)模型，建立破坏强度、劲度模量等主曲线，分析试验条件对摩尔-库伦强度模型参数的影响；2)获得不同温度及应力水平时纯剪、压剪子午面内的复数劲度模量、蠕变回复率、蠕变强度等黏弹性特征参数，获得不同试验条件对沥青混合料试件破坏强度的影响。. 本项目主要研究结论及建议如下：1)沥青混合料纯扭、压扭试验装置，需确保试件端部实际边界约束或放松条件与理论边界条件相同，纯扭试验装置应完全放松轴向约束；2)沥青混合料压扭破坏强度试验中，伴随扭转剪切变形增加，因端部受轴向约束，试件内将产生较大的轴向应力，由此难以有效预测、准确控制轴向应力，尤其是在斜向裂缝出现前后、屈服破坏阶段；3)建议在沥青混合料力学性能试验中引入纯扭剪切试验方法，以期与纯拉、纯压试验结果联合获得多子午线强度模型参数；纯扭试验推荐采用方形截面棱柱体试件，但需考虑两端约束效应的影响；4)鉴于三轴压扭试验中难以有效控制沥青混合料试件的轴向应力，建议优先用于低扭剪应变的动态黏弹性参数及低应力水平的蠕变性能试验。