Study on deformation and strength characteristics of course grained soils under wide variety of stress and strain states

为了研究和模拟细粒土在不同应力历史下不同应力状态下的力学行为，在矩形密压砾石试件上进行了两组三轴试验，试件截面为23^*23 cm，高度为58 cm。基于不同围应力水平下不同应力路径的循环三轴试验结果，提出了单调加载过程中修正应力与应变参数之间的独特关系。将这一关系与新修正的滞回规律相结合，表明所建立的模型能够合理地模拟致密砾石的循环特性。基于另外一系列三轴试验的结果，发现其蠕变行为不可忽略，应变速率的变化对单调加载性能有相当大的影响。对砂石的弹性波速也进行了研究。在Toyoura…More砂土上，用设置在矩形试件侧面的小型加速度计测得的初级波速与小幅循环加载计算得到的静态杨氏模量一致。而在粒径较大的砾石上，波速远高于静力计算值，这可能是由于土壤颗粒结构不均匀性的影响。此外，还介绍了一种装有一对水平加载板的大型真三轴仪和一种装有局部变形测量系统的中空圆柱试件（外径20 cm，内径16 cm，高30 cm）的中型三轴扭剪仪。根据初步试验结果，证实了它们在控制和测量应力应变方面的准确性。这些仪器可以全面研究垂直和水平方向上变形特性的各向异性及其因主应力方向旋转而发生的变化。少

In order to investigate and model the mechanical behavior of course grained soils under a variety of stress states with different stress histories, two series of triaxial tests were conducted on rectangular specimen (with cross-section of 23^*23 cm and height of 58 cm) of densely compacted gravel. Based on results from a series of cyclic triaxial tests following different stress paths under several levels of confining stress, a unique relationship between modified stress and strain parameters during monotonic loading was proposed. By combining this relationship with newly modified hysteresis laws, it was demonstrated that the proposed model could reasonably simulate the cyclic behaviors of dense gravel. Based on results from another series of triaxial tests, their creep behaviors were found to be not negligible, with considerable effects of change in the strain rate on the monotonic loading properties.Studies were also made on the elastic wave velocities of sands and gravel. On Toyoura … More sand, primary wave velocities measured with small accelerometers that were set on the side surface of rectangular specimen were found to be consistent with the static Young's moduli evaluated by applying small amplitude cyclic loading. On gravel with larger particle size, however, the wave velocities were much higher than the statically evaluated values, due possibly to the effects of inhomogeneity in the structure of soil particles.In addition, a large scale true-triaxial apparatus equipped with a pair of horizontal loading plates and a medium scale triaxial and torsional shear apparatus equipped with a local deformation measurement system for hollow cylindrical specimen (with outer diamete of 20 cm, inner diameter of 16 cm and height of 30 cm) were newly introduced. Based on results from preliminary tests, their accuracy in controlling and measuring stresses and strains was confirmed.These apparatuses enabled to make comprehensive studies on anisotropy of deformation properties in the vertical and horizontal directions and their changes due to rotation of principal stress direction. Less