中文摘要：

关于砂土临界状态线的传统研究主要集中f两点，临界状态线的唯一性和线性性质。然而，作为影响临界状态的重要因素，应力路径和主应力旋转一直被忽视，更鲜有将二者结合的研究。室内试验也无法在保证应力路径的同时，观测主应力旋转的存在。为了弥补这些缺憾，在多应力路径前提下，加入含主应力旋转的应力路径，对密砂进行双轴压缩试验和单剪试验的颗粒流数值模拟研究，得出以下结论：（1）密实砂土的临界状态线表现出唯一性；（2）在平均有效应力-偏应力空间和平均有效应力一比体积空间，密砂临界状态线都出现从低临界值向高临界值过渡的阶段性变化。因此，将应力路径单一化有不合理之处；而多应力路径，尤其含有特殊路径的多应力路径，将极大的影响密砂临界状态线性质，应该受到重视。

英文摘要：

Traditional research about the critical state of sand is mainly focused on the uniqueness and linearity of the critical state line. But stress path and principal stress rotation, as two important factors, have always been neglected, not to mention being studied simultaneously. And the principal stress rotation of sand cannot be observed in laboratory test. In order to make up for the shortage and combine the traditional stress path and stress path that reflects principal stress rotation, this paper conducts numerical simulations of biaxial tests and simple shear tests for dense sand by using particle flow code. According to the results, it is found that： （1） the critical state line is unique and not affected by the stress path, principal stress rotation drainage condition, initial void ratios and confining pressures~ （2） the critical state lines in both effective pressure-deviatoric stress space and effective pressure- specific volume space change from a straight line under low critical values to a curve under high critical values. Then the simplification of stress path is relatively inappropriate. Different stress paths, especially which include unconventional and specific paths will greatly influence the characteristics of critical state line. Therefore, the study about effects of different stress paths on critical state is valuable and should be paid great attention to.