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有效应力原理是土力学区别于一般固体力学的基础,是土力学的核心基石。Terzaghi有效应力原理从提出至今就一直饱受争议,特别是有关Terzaghi有效应力的近似性问题是争议的焦点。本文从有效应力原理的任务出发,阐明有效应力原理的内涵是土体可量测荷载效应—外荷载间的一般规律。指出有效应力的作用是联接土体强度、变形等可量测荷载效应与外荷载间的纽带,定义对土体强度特性和变形行为等可量测荷载效应产生直接影响的土体应力为有效应力,因此,有效应力不是唯一的,它们是土体中真实存在应力的名义表述,可以依据应力平衡原理和流体压力与土颗粒间的相互作用关系给出,不同的有效应力定义就对应不同的有效应力计算公式,从而解释了Terzaghi有效应力原理近似性的原因。提出了强度相关有效应力和变形相关有效应力(Terzaghi有效应力)的概念,严格推导了他们的计算表达式,阐述了强度相关有效应力与土体剪切强度、变形相关有效应力与土体变形的一般关系。进一步,基于摩尔库伦强度准则,推导了土体抗剪强度与Terzaghi有效应力和孔压的关系。
The principle of effective stress is the foundation of soil mechanics different from general solid mechanics and is the core foundation of soil mechanics. The Terzaghi effective stress principle has been controversial since it was proposed, and in particular the approximation of the effective stress of Terzaghi is the subject of controversy. In this paper, starting from the task of effective stress theory, the paper expounds that the connotation of effective stress principle is the measurable load effect of soil - the general rule of external load. It is pointed out that the effect of effective stress is to connect the bond between the measurable load effect and the external load, such as soil strength and deformation, to define the soil stress which is directly affected by the measurable load effect such as soil strength and deformation behavior as effective stress Therefore, the effective stress is not the only. They are the nominal expressions of real stress in soil, which can be given according to the principle of stress equilibrium and the interaction between fluid pressure and soil particles. Different effective stress definitions correspond to different effective Stress calculation formula, which explains the reason why Terzaghi effective stress principle approximation. The concepts of effective strength-related effective stress and deformation-related effective stress (Terzaghi effective stress) are proposed and their calculation expressions are strictly deduced. The relationship between strength-related effective stress and soil shear strength, deformation-related effective stress and soil deformation General relations. Further, the relationship between soil shear strength and Terzaghi effective stress and pore pressure is derived based on the molar coulomb strength criterion.