岩土弹塑性理论的加卸载准则探讨

ON LOADING-UNLOADING CRITERION OF ELASTOPLASTIC THEORY OF ROCK AND SOIL

将当前岩土弹塑性加卸载准则分为３类：基于屈服面概念的加卸载准则、应力型加卸载准则和应变型加卸载准则，指出了它们存在的问题．在岩土硬化阶段加卸载过程分析中，发现弹性应变增量、应变总量易于计算，又与塑性应变具有相关性，适于用作判断加卸载的参量．基于硬化情况下的应变增量分析，提出了一种新的应变型加卸载准则．该准则适用于岩土的硬化阶段，物理意义明确且简单适用．将该准则推广到多维及理想塑性情况，并对软化、应力洛德角变化及主应力轴旋转情况下的加卸载准则进行了讨论．

The existent loading-unloading criteria of elastoplastic theory are classified as three classes: the criterion based on the concept of yield surface, the criterion of stress type and the criterion of strain type. The shortcomings of the three classes of criteria are discussed respectively. In the light of analysis on loading-unloading process, it is discovered that strain increment and total strain are suitable to be used as judgement parameters of loading-unloading because they are easy to be calculated and correlate with plastic strain. A new loading-unloading criterion of strain type is presented for the strain increment analysis of harden stage. This criterion is of clear physical meaning, suitable to the harden stage of geomaterials and can be easily used for practical application. The criterion can be generalized to multi-dimensions and ideal-plastic case. The loading-unloading criteria used for soften, the variation of stress Lode's angle and principal stress axes rotation are discussed also.