关键词: 非饱和土, 结构性, 土骨架, 吸应力, 中性应力, 有效应力

Abstract: Because of the complexity of unsaturated soil, traditional three-phase model for unsaturated soil is oversimplified, which is unfit for interphase analysis and determination of stresses in soil. Considering a special structure in unsaturated soil , in this work, soil water system is divided into six phases and its bearing structure, named generalized soil structure, is defined. Then the differences between saturated and unsaturated soils are concluded: the bearing structures and pore liquids are different. Based on the similarity of bearing structures, a set of variables to depict the structural properties of soils is defined as generalized structural properties to describe the properties of the bearing structures of different soils. The rationality of some variables is analyzed by explaining some practical phenomena, e.g. the essence of collapse phenomenon is the weakening of the bearing structure of soil. Two representative interphase interactions are discussed and the physical significance of neutral stress is revealed, and the suction stress is redefined. Finally, it proves that the total skeleton stress in the grain is the “effective stress” for unsaturated soil.

Key words: unsaturated soil, structural property, soil skeleton, suction stress, neutral stress, effective stress