中文摘要：

为建立原状土的结构性模型,对土的初始应力及其在形成土材料过程中的作用进行了研究,并在分析常规Mohr-Coulomb准则适用性的基础上对该准则进行了修正和改进。基于土的诸多属性均依赖于其特定的结构性并最终依赖于对应的初始应力这一客观现实,给出了加（卸）载比的概念,并建立了能反映初始应力和增量应力的修正Mohr-Coulomb强度屈服准则。在此基础上,进一步给出了Pisa原状软粘土和九州火山灰撒砂法试样2种结构性土真三轴试验的各向异性屈服模型。结果表明：基于初始应力和增量应力的修正Mohr-Coulomb屈服准则以初始应力线而不是等倾线为轴线,修正准则能合理反映原状土的结构性和各向异性,且与试验结果吻合较好。

英文摘要：

In order to construct an ameliorated structural model for undisturbed soil,the initial stress state and its corresponding function in the soil aggradation process were studied detailedly,and the practicability of Mohr-Coulomb criterion was analyzed for the improvement of the criterion.Since soil＇s mechanical properties would be determined by its original structure and eventually depend on the initial stress state,the loading unloading ratio was put forward.Modified Mohr-Coulomb criterion were put forwarded in which the initial stress and the incremental stress,but not the total stress,were taken as parameters.The anisotropy yield model for true triaxial tests on the natural soft clay at Pisa and on the Shirasu specimens prepared by Kyushu ash was established.The results show that the ameliorated Mohr-Coulomb criterion based on initial stress and incremental stress with initial stress line rather than hydrostatic pressure line as its axial line can reflect structural properties and anisotropy of undisturbed soil and agree well with experiment results.