中文摘要：

利用GDS应力路径三轴试验系统与颗粒流程序PFC^2D，对2种不同颗粒粒径与级配的青岛海砂进行不同应力路径下的室内兰轴试验与数值模拟试验，探研应力路径和颗粒级配对砂土影响的细观机制。首先，进行青岛粗细砂在不同密实度与3种应力路径下的室内三轴试验，获得青岛粗细海砂的宏观力学响应，并进行初步地机制分析；然后，进行与室内试验匹配和补充的PFC^2D数值模拟试验，挖掘室内物理试验中难以得到的细观信息，如颗粒配位数，转动速度，颗粒位移等，定量地解释小同级配的砂土在不同路径下力学响应的细观原因；最后，进行不同颗粒级配砂土在循环加载路径下力学性质的PFC^2D数值试验，从细观角度分析砂土在该路径下的变形机制。

英文摘要：

The laboratory triaxial tests and numerical tests of Qingdao sea sands with different grain size gradations under different stress paths are carried out by using the GDS stress path triaxial system and particle flow code in two dimensions（PFC2D）, in order to study the mesomeehanism of the influence of stress path and grain size gradation on sands mechanical behavior. The macromechanical properties of Qingdao sea sands are obtained by three stress paths triaxial tests; and the deformation mechanism is analyzed preliminarily. Numerical tests are presented as the match and complement of laboratory tests. Some meso-information such as particle coordination number, rotational velocity and particle displacement, which cannot be obtained from laboratory tests, are extracted to explain quantitatively the meso-reasons of the peculiar mechanical behavior of sands with different gradations and stress paths. The numerical tests of different gradations particles under cyclic loads are also presented; and the macromechanical behavior and its mesomechanism are given.