论有效应力原理与有效应力

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。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,基于莫尔库仑强度准则,推导了土体抗剪强度与Terzaghi有效应力和孔压的关系。

On principle of effective stress and effective stress

The principle of effective stress is the key stone of soil mechanics, which becomes the fundamental difference between soil mechanics and solid mechanics. As it is put forward, the principle of effective stress is always in the debate, and the discussion focus is its approximation. From the analysis of the assignment of the principle of effective stress, the connotation of the principle of effective stress is illustrated as the general rule between the measurable effects and external loads. The effective stress establishes a connecting bond on the external loads and the measurable effects such as strength or deformation, which is defined as the stress that can influence the measurable effects such as strength or deformation directly. Therefore, the effective stress is not unique, which is the nominal term of real stress and can be given according to the equilibrium of forces and the interaction of soil particles. The different formulas correspond to different definitions of the effective stress, which explains the approximation of Terzaghi principle of effective stress. Then, the physical meanings of the effective stress related to the strength and the deformation are given respectively, indicating the general law of effective stress-strength or effective stress-deformation. Based on the Mohr-Coulomb strength theory, the relationship between the effective stress related to strength and the shear strength is established.