从粒间吸力特性再认识非饱和土抗剪强度理论

首先对非饱和土中吸力进行了综合分类并对各类吸力的性状进行了系统阐述 ,认为非饱和土中土颗粒间的总吸力由本征结构吸力、可变结构吸力、有效基质吸力、湿吸力和牵引力组成。基于各吸力的特性和Mohr -Coulomb强度准则 ,从理论上直接给出了非饱和土的总吸力与抗剪强度间的关系 ,这不仅从形式上统一了Bishop和Fredlund的强度公式 ,而且在内容上明确了其中各状态变量的物理意义。文中分析了非饱和土抗剪强度的组成及其影响因素。对Donald在非饱和土试验中发现的砂性土抗剪强度与基质吸力间呈山坡形的曲线关系及Gan、Escario、Fredlund等的粘性土抗剪强度和基质吸力 (含水量 )间呈非线性正比关系 ,以及对同一非饱和土因具不同初始孔隙比而具不相同的抗剪强度现象给出了令人满意的理论解释。广义抗剪强度公式客观地反映了非饱和土的强度特性

New suggestion on shear strength in unsaturated soil based on suction between grains

In this paper, the suction between grains of soils is comprehensively classified, and the properties of different suction is systematically expounded. Based on total suction and Mohr-Coulomb′s criteria of shear strength,the principle of generalized effective stress and formula of generalized shear strength are proposed.Each component of the generalized shear strength is analyzed. By generalized shear strength theory, the Bishop′s and Fredlund′s formula of shear strength are unified formally, and the physical meanings of the state variables in the formula of generalized shear strength are clear and definite.The primary factors affecting the generalized effective stress and the generalized shear strength are discussed. The experiments on nonlinear direct ratio and curred relation between shear strength and matric suction of clayey and sandy soil respectively, which were done by Donald, Gan, Escario, Fredlund, etc.,are cited to prove or to be explained by the generalized shear strength theory. This new theory based on total suction can objectively depict the shear strength of unsaturated clayey or sandy soil.