对岩土塑性变形过程中体应变与剪应变的相互作用原理的内涵做了深入的阐述，特别对塑性体应变和剪应变之间的相互作用方式，塑性体应变对抗剪能力的直接控制作用，剪缩和剪胀发生的条件，应力路径相关性是这种相互作用的综合体现及实例验证，临界状态是塑性和弹性体应变都保持不变的纯粹剪切变形过程等方面进行了论证；根据这个相互作用原理，在理论上证明了空间临界状态线的存在性和唯一性以及它与应力是无关的。

The paper proposed a principle of interaction between plastic volume strains of and shear for rock and soil. The main meanings of the principle were further explained. Especially, the manners of the interaction between plastic volume strain and shear strain, the direct effect of plastic volume strain on the resistance to shear, the conditions of generating contraction and expansion of volume, the fact that the dependence of stress path is a comprehensive performance form of the interaction between the plastic volume strain and shear and its verification, and the fact that the critical state is a pure shearing process, in which the plastic and elastic volume strains remain constant, were demonstrated. In addition, according to this principle, it was theoretically proved that the space critical state line exists and is unique and independent of the stress history.