论岩土材料屈服准则的基本特性和创新

从岩土材料的基本力学性能出发,讨论岩土材料屈服准则的基本特性和屈服准则的创新。根据国内外学者的大量实验结果,岩土材料屈服准则的基本特性为:拉压异性(SD)效应、正应力效应、静水应力效应、中间主应力效应、中间主剪应力效应、双剪应力正应力效应、双剪应力围压效应、应力角效应(应力偏张量第三不变量效应)和屈服面的外凸性。屈服准则应该满足这些基本特性,Tresca准则不符合这些条件,Mohr-Coulomb理论只能够满足部分条件,Drucker-Prager准则不能满足应力角效应。屈服准则的创新应该满足科学创新的3个要素:(1)新,前所未有;(2)比原来的准则更好;(3)能够实施、便于实际应用。总结各种力学单元体模型的发展,并以一个新的力学模型为依据,对统一强度理论补充一个拉伸破坏条件,它类似于Mohr-Coulomb准则的拉伸截断。从而将统一强度理论扩展到三向拉伸区,更能适用于岩土材料和岩土工程,也使统一强度理论在理论上更趋完整。

ON BASIC CHARACTERISTICS AND INNOVATION OF YIELD CRITERIA FOR GEOMATERIALS

A number of yield criteria have been proposed.Most yield criteria satisfy one or some basic characteristics of yield criterion.For examples,the Tresca yield criterion is a single-shear criterion;the strength difference(SD) effect,effect of normal stress,effect of intermediate principal stress,effect of intermediate principal shear stress,effect of hydrostatic stress,and the effect of twin-shear stresses are ignored.The Mohr-Coulomb yield criterion satisfies the SD effect,effect of normal stress,effect of single-shear stress and effect of hydrostatic stress.However,the effect of intermediate principal stress,effect of intermediate principal shear stress,and the effect of twin-shear stresses are not taken into account.The Drucker-Prager yield criterion can not satisfies the effect of stress angle.The basic characteristics of yield criteria are available for the research and innovation of yield criterion.The innovation of yield criterion for geomaterials has to satisfy three elements of scientific innovation as follows:(1) new(not existing before,introduced for the first time);(2) better than existing criteria;and(3) availability for application.The development of mechanical models for various yield criteria is summarized.According to a new pentahedron mechanical model,a tension-cut condition is added to the unified strength theory.The unified strength theory is extended to the tension region for geomaterials.