中文摘要：

对大理岩试样开展常规三轴加荷和峰前卸荷破坏试验，探讨加卸荷2种应力路径下大理岩在子午平面上的屈服函数形式。根据广义塑性力学理论，给出q方向上剪切屈服面和p方向上体积屈服面的数学表达式。大理岩加荷条件下剪切屈服面呈直线形式，卸荷条件下剪切屈服面呈二次抛物线形式。加荷和卸荷应力路径下大理岩都会发生体积剪胀，相应的体积屈服面可以分为压缩和剪胀2个阶段。大理岩加荷破坏过程的体积屈服面为2段不同直线形式，大理岩卸荷破坏过程的体积屈服面应采用二次抛物线形式。通过试验确定大理岩屈服函数，不仅能反映应力路径变化对岩石屈服的影响，还能够反映岩石各向异性性质，避免人为假定屈服函数的弊端。与加荷应力路径相比，卸荷应力路径下塑性剪应变和塑性体应变增加的更快，后继屈服面迅速向极限屈服面发展，进一步说明卸荷破坏的突发性和剧烈性。

英文摘要：

Conventional triaxial experiments and unloading experiments of marble were carried out. The forms of yielding functions on the meridian plane were discussed under different loading and unloading stress paths. According to the generalized theory of plastic mechanics,the mathematical expressions of the yielding surface of shearing in q direction and the volumetric yielding surface in p direction were given. Results show that the yielding surface for shearing was linear under the loading stress path, was a parabola under the unloading stress path. The volume of the marble samples dilated under both the loading and unloading stress paths. The volumetric yielding surface was divided into the compression stage and the expansion stage. The volumetric yielding surface of marble under the loading stress path made up by two linear segments and under the unloading stress path was a parabola. The yield function determined according to the test results reflected the impact of the stress path changes and the anisotropy of rock and avoided the disadvantages of assumed ones. The plastic shear strain and plastic volume strain increased faster under the unloading stress path than under the loading path. The subsequent yield surface developed to the limit yield surface very quickly. These results illustrate that the unloading failure occurring more suddenly.