Asphalt concrete (AC) material characterization is usually performed on laboratory prepared specimens, a procedure that does not ensure that the material tested reproduces the aggregates arrangement of the field material. Currently, field specimens are tested on cores in the Indirect Tensile Test (IDT) and on cylindrical specimens cored horizontally from relatively thick AC layers. As AC materials may exhibit cross anisotropy, testing cylindrical specimens requires two specimens, one in the vertical direction and the other in the horizontal direction. The above limitations can be overcome by testing prismatic field specimens in a triaxial cell with controllable vertical stress and confining pressure. The paper presents a study of the cross-anisotropic relations in two different specimen shapes, cylindrical and prismatic, and shows that prismatic specimens are preferred in the case of cross anisotropy.

The use of the triaxial cell offers the possibility of applying different 2D stress paths and measuring the resulting 3D deformations. Creep and recovery tests on a prismatic specimen cut from a test section are conducted to illustrate the feasibility of the procedure. Before embarking in an extensive research project, six creep and recovery tests are conducted, under different stress paths that represent the closest stress/strain condition under a wheel load. The stress/strain conditions were kept within the small strain range, within the linear nonlinear stages. The linear viscoelasticity for cross-anisotropic materials is formulated, implying the derivation of four independent creep compliance functions. The test results are analyzed using numerical integration. The analyses show that the creep compliance functions vary with the stress/strain level, even in the so-called small strain range. Recommendations for further research are suggested.

沥青混凝土（AC）的材料表征通常是在实验室准备的标本上进行的，该程序不能确保所测试的材料能够再现野外材料的骨料排列。当前，在间接拉伸试验（IDT）中对岩心样品进行了测试，并在相对较厚的AC层中水平取芯的圆柱状样品中进行了测试。由于交流材料可能表现出交叉各向异性，因此测试圆柱形样品需要两个样品，一个在垂直方向，另一个在水平方向。通过在可控的垂直应力和围压下在三轴单元中测试棱形场样本可以克服上述限制。本文介绍了两种不同形状的样品（圆柱和棱柱形）的横各向异性关系，

三轴单元的使用提供了施加不同2D应力路径并测量所得3D变形的可能性。对从测试部分切下的棱柱形样品进行了蠕变和恢复测试，以说明该方法的可行性。在着手进行广泛的研究项目之前，进行了六次蠕变和恢复测试，它们在不同的应力路径下代表了车轮载荷下最接近的应力/应变条件。在线性非线性阶段内，应力/应变条件保持在较小的应变范围内。制定了各向异性材料的线性粘弹性，暗示了四个独立的蠕变柔量函数的推导。使用数值积分分析测试结果。分析表明，即使在所谓的小应变范围内，蠕变柔度函数也会随应力/应变水平而变化。建议进一步研究的建议。