Relationship Between Structural Strength And Structural Yield Pressure Of Loess

Loess is kind of special soil which was widely spread in Northern China, How to determine the preconsolidation pressure of loess, explore the distribution of preconsolidation pressure and analysis of its relations with the structural strength is a discovery of the development of the soil mechanics, while playing a guiding role to the engineering practice, all above are very meaningful.Paper focused on the unsaturated loess, by means of high pressure consolidation and direct shear test, studied on the relationship of structural strength and structure yield pressure of unsaturated loess, and the main results were as follows:(1) There was a well Power function relationship of structure yield pressure and moisture content, the structure yield pressure decreased with the increasing of moisture content. Determination of the structure yield pressure in various ways, the results of Casagrande,Joes et al and Burmister were on the close, and the result of Lebert and Horn was minimum.(2) When the moisture content was lower,the residual strength of undisturbed loess is much smaller when less pressure on the loess , the residual strength of remodeled loess increased gradually with the increasing of normal stress. Some remodeled ones'residual strength was higher than undisturbed ones'when under the same moisture content and dry density.(3) There was a well Power function relationship of structural strength and moisture content and a linear relationship of structural strength and cohesion, when the dry density is smaller and clay content is lower, the increment of cohesion was larger than that of structural strength along with reducing of moisture content, instead, the opposite results.(4) The increment of structural yield pressure was larger than that of the structural strength along with the reducing of moisture content, there was a linear relationship between the increment of the structural strength and the structural yield pressure, and under the co-action of normal stress and horizontal shear stress, the structure of loess was beginning to failure before the normal stress reached the structural yield pressure.(5) The OCR value of loess under the same depth decreased along with the increasing of moisture content, showing a well power function relationship, not a fixed value as the general concept of soil mechanics.(6) Defined S to be an unstable structural strength factor of loess, the value of S showed the size of unstable structural strength factor of loess.