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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。
The traditional plastic dilatancy model is based on the coaxial plastic flow law when describing the relationship between stress ratio and plastic strain increment, so that the dilatancy of soil is only related to the stress ratio. Numerous experimental results show that stress-strain is non-coaxial in the plastic flow process under complicated stress conditions involving the change of principal stress axis. Therefore, non-coaxiality can not be neglected when analyzing dilatancy characteristics of sand. In order to study the influence of non-coaxial to the dilatancy characteristics of sand under complicated stress conditions with varying principal stress axis, a series of tests of the fixed-axis shear test, pure principal stress axis rotation test and combined loading test. The experimental results show that the stress-strain non-coaxial path under different stress paths will cause the curve of the dilatancy to deviate from the Rowe line. The modified non-coherent dilatancy equation proposed by Gutiereez can correct the non-coaxial deviation and make the Rowe shear Expansion equations apply to more complicated loading conditions involving rotation of the principal stress axis.