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

为了研究和模拟不同应力历史下粗粒土的力学行为，对密实砾石矩形试样（截面为23^*23 cm，高为58 cm）进行了两组三轴试验。基于一系列不同应力路径下的循环三轴试验结果，提出了单调加载条件下修正应力与应变参数之间的唯一关系。通过将该关系与新修正的滞回规律相结合，表明所提出的模型能够合理地模拟密实砾石的循环特性。根据另一系列三轴试验的结果，发现它们的蠕变特性是不可忽略的，应变率的变化对它们的单调加载特性有相当大的影响，并对砂和砾石的弹性波速进行了研究。关于丰浦 关于我们 砂，一次波的速度与小加速度计，设置在矩形试样的侧面被发现是一致的静态杨氏模量评估通过施加小振幅循环加载。然而，在粒径较大的砾石上，波速远高于静态评估值，这可能是由于土颗粒结构的不均匀性的影响。大型真三轴仪和中型三轴扭剪仪，前者配有一对水平加载板，后者配有空心圆柱试样局部变形测量系统（外径20 cm，内径16 cm，高30 cm）。根据初步试验结果，确认了该仪器在控制和测量应力应变方面的准确性，能够全面研究垂直方向和水平方向变形特性的各向异性及其随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