传统塑性剪胀模型在描述应力比和塑性应变增量关系时都是基于共轴塑性流动法则，从而认为土体的剪胀性仅与应力比有关。大量试验结果表明，在涉及主应力轴变化的复杂应力条件下塑性流动过程中应力-应变是非共轴的，因而在分析砂土剪胀特性时非共轴是不可忽视的因素。为了研究主应力轴变化的复杂应力条件下非共轴对砂土剪胀特性的影响，利用空心圆柱仪对饱和砂土进行了一系列定轴剪切试验、纯主应力轴旋转试验以及组合加载试验。试验结果表明，不同应力路径下应力-应变非共轴都会引起剪胀曲线偏离Rowe直线，通过Gutiereez提出的考虑非共轴因子的修正剪胀方程可以修正非共轴引起的偏差，从而使得Rowe剪胀方程适用于涉及主应力轴旋转等更加复杂的加载条件。

Traditional plastic dilatancy models are based on coaxial plastic flow rule when describing relations between the stress ratio and plastic strain increment, in which stress-dilatancy behavior of soil only depends on stress ratio. A large number of test results show that the stress and strain are non-coaxial during plastic flow under complex stress conditions involving principal stress rotation; so the non-coaxiality cannot be ignored when analyzing stress-dilatancy behavior of soil. In order to investigate the effects of non-coaxiality on the stress-dilatancy behavior of sand under complex stress conditions involving principal stress axes rotation, a series of fixed principal stress axes shear tests and pure principal stress rotation tests and combined loading tests are conducted on the saturated sand using a hollow cylinder apparatus. The test results indicate that the stress-strain non-coaxiality would result in the deviation between the stress-dilatancy curves and Rowe-line under different stress paths, which can be modified through the Gutiereez’s modified dilatancy equation by introducing a non-coaxiality factor. In this way, Rowe’s stress-dilatancy equation can be made more applicable to loadings involving principal axes stress rotation.